FEASIBILITY STUDY OF ULTRASOUND MEASUREMENTS ON THE HUMAN 
LUMBAR SPINE 
 
 
Except where reference is made to the work of others, the work described in this thesis is 
my own or was done in collaboration with my advisory committee. This thesis does not 
include proprietary or classified information. 
 
 
 
 
 
                                     
Phani Bhushan Pothuganti Virabadra Venkat 
 
 
 
Certificate of Approval: 
 
 
 
 
Ram Gudavalli                                                      P.K. Raju, Chair              
Adjunct Associate Professor                                 Thomas Walter Professor                                      
National University of Health Sciences                Mechanical Engineering                                  
Associate Professor                                                      
Palmer Center for Chiropractic Research 
 
 
                                                                                    
 
Dan Marghitu                                                        Joe F. Pittman  
Professor                                                               Interim Dean 
Mechanical Engineering                                       Graduate School 
 
 
FEASIBILITY STUDY OF ULTRASOUND MEASUREMENTS ON THE HUMAN 
LUMBAR SPINE 
 
   Phani Bhushan Pothuganti Virabadra Venkat 
 
 
 
 
A thesis  
Submitted to 
 the Graduate Faculty of  
Auburn University  
in Partial Fulfillment of the  
Requirements for the  
Degree of  
Master of Science 
 
 
 
 
Auburn, Alabama 
December 15, 2006 
 iii
FEASIBILITY STUDY OF ULTRASOUND MEASUREMENTS ON THE HUMAN 
LUMBAR SPINE 
 
 
Phani Bhushan Pothuganti Virabadra Venkat 
 
 
 
Permission is granted to Auburn University to make copies of this thesis at its discretion, 
up on request of individuals or institutions and at their expense. The author reserves all 
publication rights. 
 
 
 
 
 
       
                                    Signature of Author 
 
 
 
 
             Date of Graduation  
     
 
 
 
 
 
 
 
 
 
 
 
 
 iv
VITA 
 
Phani Bhushan Pothuganti Virabadra Venkat, only son of LaxmiKantham 
Pothuganti and Vidyavathi Pothuganti, was born in Banswada, Nizamabad District, 
Andhra Pradesh, India on November 07, 1982. He finished his high school from 
Dilsukhnagar Public School and later joined in Ideal Junior College for his Intermediate 
Education. Later he went to Bangalore for pursuing his Bachelor of Engineering in 
Mechanical at Shirdi Sai Engineering College, Visveswaraiah Technological University. 
After graduating from Shirdi Sai Engineering College he then entered the Graduate 
school at Auburn University in the Department of Mechanical Engineering in August 
2004. While at Auburn University, he was a teaching assistant for various courses in the 
engineering and business disciplines. He also worked as a research assistant under the 
valuable guidance of Dr. P.K. Raju and Dr. Ram Gudavalli and graduated in September 
2006 with a Master of Science in Mechanical Engineering.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 v
THESIS ABSTRACT 
FEASIBILITY STUDY OF ULTRASOUND MEASUREMENTS ON THE HUMAN 
LUMBAR SPINE 
Phani Bhushan Pothuganti Virabadra Venkat 
 
Master of Science, December 15, 2006 
(B.E., Vishveswaraiah Technological University, 2004) 
167 Typed Pages 
Directed by P. K. Raju 
 
This study is a part of a research project that aims to measure the variation in the 
intervertebral distance of patients that are subjected to lumbar flexion-distraction 
chiropractic manipulation. The purpose of this research project is to evaluate the 
feasibility of using a B-scan image generated by a customized ultrasonic design to 
measure the distance between the adjacent lumbar vertebrae  
 Previous research using the same customized ultrasonic design was done and it 
was found that the reproducibility of the measurement expressed in terms of the 
coefficient of variation for measurements of the artificial model was found to be better 
than 0.1% (0.013 mm standard error), whereas for measurements of human subjects it 
was better than 1% (0.1 mm standard error). The excellent results obtained from the test 
conducted on the artificial model verify the reliability of the testing instrumentation and 
methodology. Before this system is routinely used in clinical situations it needs to
 vi
undergo further testing process. This system was tested to measure the distance between 
the lumbar vertebrae of the artificial spine model by scanning the transverse process 
instead of the spinous process. This experimentation showed us a few drawbacks and 
certain limitations of using this ultrasonic design equipment.  
As a consequence we employed the commercially available high-end ultrasonic 
device, Philips HDI 5000. Several experiments were conducted on the artificial spine 
model using this ultrasound machine, such as measuring the distance between the 
transverse process of the lumbar vertebrae, measuring the depth of the transverse process 
from the surface of the gelatin solution and measuring the width of each transverse 
process. Experiments were also made to measure the width of each spinous process of the 
lumbar vertebrae and these measurements were then compared with the measurements 
obtained from our customized ultrasound system and also with the physical 
measurements from the vernier calipers. Measurements obtained from the two ultrasound 
systems and vernier calipers were very close. 
Further tests were conducted on the customized ultrasound system to measure the 
distance between the lumbar vertebrae (L1, L2 and L3) by imaging the spinous process in 
a traction conditioned situation. To simulate the traction in the artificial spine, 1 mm rings 
were used and were placed in-between the vertebral body and the distance was measured. 
The distance between the lumbar vertebrae was increased by 1 mm for each set of 
experiments. The results obtained showed that the custom-built ultrasonic system can be 
used to measure the distance between the lumbar vertebrae by imaging the spinous 
process in a traction condition. However, a commercially available sophisticated system 
is needed if the distance between the lumbar vertebrae by imaging the transverse process. 
 vii
ACKNOWLEDGEMENTS 
I would like to express my deepest gratitude towards Dr. P.K. Raju and Dr. Ram 
Gudavalli for their support, motivation and guidance throughout the research work. I 
would like to thank Dr. Dan Marghitu for being a positive support throughout my 
research work and for serving as a committee member. I would also like to thank Dr. 
David Beale and his student, David Branscomb, for their help in manufacturing the slider. 
I would like to thank Dr.Cramer at NUHS on the advice of gel preparation, 
support of equipment and travel from Cox funds at NUHS and Auburn University. I 
would also like to extend my appreciation to Dr. Holly McCort and Dr. Hudson for their 
valuable time and help in conducting the experiments at veterinary school facility, AU. 
  I wish to express my gratitude to all my family members for being supportive and 
keeping faith in me at all times.  I am highly indebted to my parents, for unconditional 
love and support, and for always encouraging me to follow my dreams. They have 
dedicated a great deal of their life to keeping me happy, healthy and successful, and for 
that I am forever grateful and dedicate this thesis to them. 
A special thanks to Sri Harsha, who was always there by my side when I needed 
the most and provided me with constant support, love and encouragement. Big thanks to 
all my friends for their support and encouragement. Finally, I want to thank god for 
guiding me and giving me the encouragement, strength and will to pursue my goal in 
accomplishing this research work and having the pleasure to see it terminate fruitfully. 
 viii
Style manual or journal used: Journal of ASME 
 
Computer software used: Microsoft word 2003 
 ix
 
TABLE OF CONTENTS 
 
LIST OF FIGURES????..??????????????????????xiii 
LIST OF TABLES??????????????????????????...xvii 
1. INTRODUCTION .......................................................................................................... 1 
1.1 Overview................................................................................................................... 1 
1.2 Main Objective: ........................................................................................................ 4 
2. ULTRASONIC WAVE PROPAGATION THEORY.................................................... 6 
2.1 Evolution of Ultrasonic?s.......................................................................................... 6 
2.2 Characteristics of Ultrasonic Waves......................................................................... 8 
2.3 Basic Concepts........................................................................................................ 10 
2.4 Types of Ultrasonic Waves..................................................................................... 13 
2.5 Behavior of Ultrasonic Waves at Boundaries......................................................... 18 
2.6 Attenuation of Ultrasonic Waves............................................................................ 22 
3. TESTING TECHNIQUES AND DATA PRESENTATION FOR ULTRASONIC 
     TESTING..................................................................................................................... 25 
3.1 Introduction............................................................................................................. 25 
 x
3.2 Pulse Echo Technique:............................................................................................ 25 
3.3 Through Transmission Technique .......................................................................... 29 
3.4 Data Presentation .................................................................................................... 30 
3.4.1 A-Scan Presentation......................................................................................... 30 
3.4.2 B-Scan Presentation......................................................................................... 32 
3.4.3 C-Scan Presentation......................................................................................... 33 
3.4.4 M-Scan Presentation:....................................................................................... 34 
4. ULTRASONIC TRANSDUCERS ............................................................................... 35 
4.1 Introduction............................................................................................................. 35 
4.2 Construction of a Simple Ultrasonic Transducer:................................................... 35 
4.3 Principle of Operation............................................................................................. 37 
4.4 Resolution & Sensitivity of Ultrasonic Transducers .............................................. 37 
4.5 Piezoelectric Transducers ....................................................................................... 40 
4.5.1 Contact, Immersion or Air-Coupled Transducers............................................ 41 
4.5.2 Normal or Angled Beam Transducers ............................................................. 43 
4.5.3 Single and Multiple Element Transducers....................................................... 44 
5. LUMBAR SPINE ANATOMY.................................................................................... 50 
5.1 Spinal Column ........................................................................................................ 51 
 xi
5.2 Vertebrae................................................................................................................. 53 
5.3 Intervertebral Disc .................................................................................................. 54 
5.4 Soft Tissue surrounding the lumbar spine .............................................................. 55 
5.5 Facet Joint ............................................................................................................... 56 
6. INSTRUMENTATION AND METHODOLOGY ...................................................... 58 
6.1 Background Information......................................................................................... 58 
6.2 Instrumentation ....................................................................................................... 59 
6.3 Working of the ultrasonic system ........................................................................... 62 
6.4 Scanning Procedure ................................................................................................ 65 
6.5 Data Analysis.......................................................................................................... 67 
6.6 Spatial Resolution, Encoder Resolution ................................................................. 69 
6.7 Selection of the Transducer .................................................................................... 70 
6.8 Test Sessions........................................................................................................... 71 
6.8.1 Tests on the Artificial Spine Model Using Customized Ultrasound System... 71 
6.8.2 Tests on the Artificial Spine Model in VET School ? Auburn University...... 75 
6.8.3 Simulating the Traction in the Artificial Lumbar Spine .................................. 87 
7. RESULTS AND DISCUSSION................................................................................... 89 
7.1 Tests on the Artificial Spine Model........................................................................ 89 
7.2 Tests on Artificial Spine Model ? Simulating the traction in the model. ............... 95 
 xii
8. CONCLUSIONS AND POTENTIAL FOR FUTURE DEVELOPMENT................ 104 
REFERENCES????????????????????????????108 
APPENDIX A. LITERATURE REVIEW??...???????????????112 
 
APPENDIX B. TECHNICAL SPECIFICATIONS OF ULTRASOUND SYSTEM?..117 
 
APPENDIX C. LABVIEW PROGRAMS AND DLL?????????????123 
APPENDIX D. COMMERCIAL ULTRASOUND SYSTEMS?????????..136 
 
APPENDIX E. WEB REFERENCES???????????????????.149 
 
 
 
 xiii
 
 
 
 
 
LIST OF FIGURES 
 
Figure 1.2: Intervertebral distance a) after and b) before flexion-distraction treatment..... 4 
Figure 2.1: Acoustical Frequency Spectrum....................................................................... 8 
Figure 2.2: Relation between resolution and penetration depth ....................................... 10 
Figure 2.3: Harmonic Oscillation ..................................................................................... 11 
Figure 2.4 - Longitudinal Wave........................................................................................ 13 
Figure 2.5: Longitudinal wave propagation in a material................................................. 14 
Figure 2.6: Transverse or Shear Wave.............................................................................. 14 
Figure 2.7: Transverse or Shear Wave propagation in a material..................................... 15 
Figure 2.8: Surface Wave ................................................................................................. 15 
Figure 2.9: Normal incidence of an ultrasonic wave on a smooth boundary ................... 19 
Figure 3.1: Basic schematic of pulse-echo testing technique. .......................................... 26 
Figure 3.2: Basic Design of Pulse Echo Technique.......................................................... 28 
Figure 3.3: Schematic of Through Transmission Technique............................................ 29 
Figure 3.4: Scanning Procedure of the Specimen............................................................. 31 
Figure 3.5: A-scan Presentation........................................................................................ 32 
Figure 3.6: B-Scan Presentation ....................................................................................... 33 
Figure 3.7: C-Scan Presentation ....................................................................................... 34 
Figure 4.1: Axial Resolution Effect.................................................................................. 38 
Figure 4.2: Cylindrically and spherically focused transducers......................................... 42 
 xiv
Figure 4.3 - a) Normal Beam Transducers b) Angled Beam Transducers........................ 44 
Figure 4.4: Components of a single element transducer................................................... 44 
Figure 4.5: Components of a Dual Element Transducer................................................... 45 
Figure 4.6: Electronic phasing used to steer a sound field ............................................... 47 
Figure 4.7: Electronic phasing used to create a focused sound field................................ 48 
Figure 4.8: Commercially available phased array transducers ......................................... 49 
Figure 5.1: Human Spine .................................................................................................. 50 
Figure 5.2: Lumbar Spine a) General Structure, b) Ligaments around the vertebrae....... 52 
Figure 5.3 ? Parts of a Lumbar Vertebrae......................................................................... 54 
Figure 5.4: Vertebrae with Intervertebral Disc................................................................. 55 
Figure 5.5 ? Cross Section  of Lumbar Spine Segment.................................................... 56 
Figure 5.6: Facet Joint....................................................................................................... 57 
Figure 6.1: Ultrasonic Testing System.............................................................................. 60 
Figure 6.2: Schematic representation of the functioning of the ultrasonic board............. 62 
Figure 6.3: Scanning assembly configuration................................................................... 62 
Figure 6.4: Slider holding the transducer at a fixed position............................................ 63 
Figure 6.5: Displacement of the slider along the base slot ............................................... 64 
Figure 6.6: Rubber sheet glued at the bottom of the base................................................. 65 
Figure 6.7: B-scan (intensity plot) representation and instrumentation settings .............. 66 
Figure 6.8: Front panel of the data analysis program ....................................................... 68 
Figure 6.9: Zoom in image of Figure 6.8.......................................................................... 68 
Figure 6.10: Artificial lumbar spine in the gelatin solution.............................................. 71 
Figure 6.11: New slider with large diameter hole............................................................. 72 
 xv
Figure 6.12: Scanning procedure of artificial sample....................................................... 73 
Figure 6.13: Philips HDI 5000 Ultrasound System .......................................................... 75 
Figure 6.14: Artificial Lumbar Spine in Gelatin Solution ................................................ 77 
Figure 6.16: Width of the L1 transverse process on the left of the vertebral body .......... 80 
Figure 6.17: Distance between the L1 & L2 transverse process....................................... 81 
Figure 6.18: Depth of L4 and L5 transverse process from the gelatin surface................. 82 
Figure 6.19: Length of the L4 Spinous process ................................................................ 83 
Figure 6.20: Length of the L4 spinous process................................................................. 84 
Figure 6.21: Vertical Measurements between the L3 and L4 lumbar vertebra ................ 85 
Figure 6.22: Dual Image of L1, L2 and L3 vertebrae....................................................... 86 
Figure 6.23: L1, L2 and L3 Vertebrae with no 1mm rings............................................... 88 
Figure 6.24: L1, L2 and L3 vertebrae with 5 mm rings in between ................................. 88 
Figure 7.1: Image of L4 Vertebra and transverse process of L5 Vertebra  
                   from Philips HDI 5000 Ultrasound System................................................... 89 
Figure 7.2: Depth measurement of L4 and L5 transverse processes ................................ 90 
Figure 7.3: Image of the spinous process of L4 vertebra using our ultrasound system.... 92 
Figure 7.4: Comparison Graphing two ultrasound systems and vernier calipers ............. 94 
Figure 7.5: Distance between the L2 and L3 spinous process.......................................... 97 
Figure B.1: PCIUT3100 board........................................................................................ 117 
Figure B.2: MAGMA's 2 Slot Cardbus-to-PCI Expansion Systems .............................. 119 
Figure B.3: Immersion Ultrasonic Transducer ............................................................... 121 
Figure B.4: Signal waveform and frequency spectrum  
                   of a Video Scan 5 MHz transducer.............................................................. 121 
 xvi
Figure B.5: Final Assembly ............................................................................................ 122 
Figure D.1: LOGIQ Book XP from GE.......................................................................... 137 
Figure D.2: Philips HD 11 XE Ultrasound System ........................................................ 139 
Figure D.3: Sonoline G 20 Ultrasound, gray scale imaging........................................... 142 
Figure D.4: Aloka SSD 4000 Utrasound System............................................................ 144 
Figure D.5: Pyramid 800 Ultrasound System................................................................. 145 
Figure D.6: Cart Base Ultrasound system UF-850XTD from TeraRecon...................... 146 
 
 xvii
 
 
 
 
 
 
LIST OF TABLES 
 
Table 2.1: Wave speed, density, and acoustic impedance for some materials ................. 17 
Table 2.2: Average Attenuation Coefficients for soft tissue............................................. 24 
Table 4.1: Effect of axial resolution, lateral resolution and penetration of the 
                 ultrasonic beam as a function of the frequency ............................................... 39 
Table 7.1: Depth of the Transverse Process...................................................................... 90 
Table 7.2: Width of the Transverse Process ..................................................................... 91 
Table 7.3: Distance between the Transverse Process ....................................................... 91 
Table 7.4: Length of the Spinous Process from Philips HDI 5000................................... 92 
Table 7.5: Length of spinous process from our ultrasound system .................................. 93 
Table 7.6: Comparison of Spinous Process Length.......................................................... 93 
Table 7.7: Difference in spinous process length obtained from vernier calipers 
                  and philips system........................................................................................... 94 
Table 7.8: Difference in spinous process length obtained from vernier calipers 
                  and the customized ultrasonic system............................................................. 95 
Table 7.9: Distance between the Lumbar Vertebra with no 1mm rings ........................... 96 
Table 7.10: Distance between the lumbar vertebra with 1mm rings ................................ 98 
Table 7.11: Distance between the lumbar vertebrae with 2 mm rings.............................. 98 
Table 7.12: Distance between the lumbar vertebrae with 3 mm rings.............................. 99 
Table 7.13: Distance between the lumbar vertebrae with 4 mm rings.............................. 99 
 xviii
Table 7.14: Distance between the lumbar vertebrae with 5 mm rings.............................. 99 
Table 7.15: Difference in the spinous processes distance when 1 mm rings are used ... 100 
Table 7.16: Difference in the spinous processes distance when 2 mm and  
                    1mm rings are used ..................................................................................... 100 
Table 7.17: Difference in the spinous processes distance when 2 mm and 
                   3 mm rings are used ..................................................................................... 101 
Table 7.18: Difference in the spinous processes distance when 3 mm and  
                    4 mm rings are used .................................................................................... 101 
Table 7.19: Difference in the spinous processes distance when 4 mm and 
                    5 mm rings are used .................................................................................... 101 
Table 7.20: Difference in normal spinous processes distance and when 
                   1 mm rings are used ..................................................................................... 102 
Table 7.21: Difference in normal spinous processes distance and when  
                   2 mm rings are used ..................................................................................... 102 
Table 7.22: Difference in normal spinous processes distance and when 
                   3 mm rings are used ..................................................................................... 102 
Table 7.23: Difference in normal spinous processes distance when 
                   4 mm rings are used ..................................................................................... 103 
Table 7.24: Difference in normal spinous processes distance when  
                    5 mm rings are used .................................................................................... 103 
 
  1 
 
1. INTRODUCTION 
 
1.1 Overview 
 Ultrasound has been accepted as a potential imaging utility since the 1940s. Since 
then, ultrasound has been applied for various medical purposes. Today ultrasound is 
ranked as a major diagnostic tool in medicine. Its applications are constantly expanding 
in new diagnostic areas. Obviously, continuous change and continuous improvement are 
the role in the field of diagnostic ultrasound equipment 
1
.All the modern clinical 
ultrasound machines currently in commercial use are based on the construction of an 
image from the backscattered ultrasound waves 
2
.  
A variety of medical technicians including radiographers, physiological 
measurement technicians, specialist technicians in ultrasound, medical engineers and 
physicists play role a in medical diagnostic ultrasound. A well-trained level of expertise 
in ultrasound is definitely needed for any ultrasound examination procedure. 
 There are two main types of ultrasonic measurement. First, the Quantitative 
Ultrasound (QUS), which is a reliable, fast and cost-effective method of determining 
tissue composition, assess muscle thickness and non-invasively determine bone-mineral-
density, risk of fractures, skin pathology, body fat and muscle thickness. In this kind of 
measurement, ultrasonic waves pass through the site under investigation and reflect back 
from different kinds of tissue and bone components. The strength of the reflected waves 
  2 
 
is then correlated to measure tissue composition, bone-mineral-density and body fat 
3, 4, 5
.  
The Second type of measurement is known as Diagnostic Ultrasound (DUS), which 
covers the imaging aspects of the tissues and skeletal structures 
6, 7, 8, 9, 10
. In these types 
of measurements, a narrow beam of ultrasound is focused onto the tissues, bones, 
muscles and different body organs, and a pictorial representation of the area of interest 
can be obtained and used for evaluation and diagnosis purposes 
1
. The fundamental 
mechanism that creates the ultrasound image is the strength of the reflected waves 
(echoes). The frequency of the ultrasound used for diagnosis depends on a number of 
factors, including the properties of tissues or organs examined, depth of the tissues or 
organs from the skin surface, quality of image required and many others. 
 This research project falls under the diagnostic ultrasound (DUS) measurement. 
We image the lumbar vertebrae of the human spine and calculate the distance between 
them before and after the flexion-distraction chiropractic manipulation. In the 
chiropractic medicine, it is of major importance to calculate the variations in 
intervertebral distance when patients are treated by the Cox Flexion-Distraction 
technique.  
  3 
 
 
Figure 1.1: Cox Flexion Distraction Table 
Flexion-distraction is an excellent technique for the treatment of middle and lower 
back pain. It is a gentle and extremely effective technique that helps to decompress the 
spine and remove pressure on vertebral discs. In addition, it restores range of motion to 
the spine and realigns the vertebrae. Flexion-distraction is the treatment of choice for 
many patients suffering with back pain. Most patients experience relief after 3 to 5 
treatments. The treatments are comfortable and performed on a fully adjustable 
ergonomic table that can be fit to all body types including pregnant women. Flexion- 
distraction should be considered for those whose pain has not responded to other types of 
care. This treatment can make all the difference in removing and managing your pain 
permanently 
34
. 
Theoretically, the traction or distraction of the disc combined with isolation and 
gentle pumping of the involved area allows the central area of the disc, the nucleus 
pulposus, to assume its central position in the disc. Flexion-distraction is thought to 
  4 
 
increase the intradiscal height and reduce intradiscal pressures 
35
. The largest vertebral 
mobility under this technique is found in the lumbar and cervical spine section. 
a b 
 
Figure 1.2: Intervertebral distance a) after and b) before flexion-distraction treatment. 
To measure the intervertebral distance before and after the flexion-distraction 
treatment, we can use MRI, X-Ray or Computed Tomography (CT), but these techniques 
are expensive, ionizing and complex in setup and operations. An inexpensive, sensitive, 
portable and non-invasive technique for measuring this intervertebral distances. This can 
be achieved through the application of ultrasound technique. 
Literature search revealed a lack of this kind of ultrasound application to calculate 
the intervertebral distance before, during and after the flexion distraction technique. On 
the other hand, many investigations were found in measuring the intervertebral distance 
during the diurnal changes 
7, 8
 and weight bath therapy 
11
.  
1.2 Main Objective: 
The main objective of this research project is to measure the variation in 
intervertebral distances of patients who are subjected to lumbar flexion-distraction 
chiropractic manipulation. 
  5 
 
The specific goals that will contribute to achieve the objective are: 
? Measuring the distance between the vertebrae by scanning the transverse process 
instead of the spinous process. 
? Conducting the experiments on Phillips HDI 5000 CV, ultrasound system and 
comparing some of the values obtained with our customized built ultrasound 
system and evaluating the accuracy of our system. 
? Simulating the traction condition in the artificial spine using 1mm metal rings and 
evaluating the reliability of the custom-built ultrasonic design and testing 
procedure to consistently locate the spinous processes and measure the distance 
between them. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  6 
 
2. ULTRASONIC WAVE PROPAGATION THEORY 
 
2.1 Evolution of Ultrasonic?s 
 
 Like so much else in engineering, ultrasonic theory has undergone its greatest and 
most rapid development in the 19
th
 and 20
th
 centuries. In 240 B.C., the Greek philosopher 
Chtysippus, speculated that sound took the form of waves. The father of acoustics, 
Galileo Galilei, and Marin Mersenne developed the first laws governing sound in the 16
th
 
and 17
th
 centuries. Sir Isaac Newton developed the first mathematical theory of sound in 
1686. Newton?s theory allowed for wave phenomena such as diffraction. Later Newton?s 
theory was expanded by Euler, Lagrange, and d?Alembert which led to the development 
of the wave equation. The wave equation developed by Euler, Lagrange, and d?Alembert 
allowed sound waves to be represented mathematically 
12
.  
 In 1880, Curie discovered the crystals which can convert the ultrasonic energy to 
electrical energy. The inverse effect known as the piezoelectric effect, converting the 
electrical energy into ultrasonic energy, was discovered by Lippmann in 1881 
12
. After 
these discoveries, one of the more practical ultrasonic endeavors was the detection of 
icebergs at sea, developed in 1912 as a direct response to the sinking of the Titanic. This 
technique of sending sound waves through water and observing the returning echoes to 
characterize submerged objects inspired early ultrasound investigators to explore ways to 
apply the concept to medical diagnosis 
37
. In 1929 and 1935, Sokolov studied the use of 
  7 
 
ultrasonic waves in detecting metal objects. Mulhauser, in 1931, obtained a patent for 
using ultrasonic waves, using two transducers to detect flaws in solids. Firestone (1940) 
and Simons (1945) developed pulsed ultrasonic testing using a pulse-echo technique.  
Shortly after the close of World War II, researchers in Japan began to explore the 
medical diagnostic capabilities of ultrasound. The first ultrasonic instruments used an A-
mode presentation with blips on an oscilloscope screen. That was followed by a B-mode 
presentation with a two dimensional, gray scale imaging.  
This Japanese achievement in ultrasound was relatively unknown in the United 
States and Europe until the 1950s. The same researchers then presented their findings on 
the use of ultrasound to detect gallstones, breast masses, and tumors to the international 
medical community. Japan was also the first country to apply Doppler ultrasound, an 
application of ultrasound that detects internal moving objects, such as blood coursing 
through the heart for cardiovascular investigation.  
Ultrasound pioneers working in the United States contributed many innovations 
and important discoveries to the field during the following decades. Researchers learned 
to use ultrasound to detect potential cancer and to visualize tumors in living subjects and 
in excised tissue. Real-time imaging, another significant diagnostic tool for physicians, 
presented ultrasound images directly on the system's CRT screen at the time of scanning. 
The introduction of spectral Doppler and later color Doppler depicted blood flow in 
various colors to indicate speed of flow and direction. The United States also produced 
the earliest hand-held "contact" scanner for clinical use, the second generation of B-mode 
  8 
 
equipment, and the prototype for the first articulated-arm hand-held scanner, with 2-D 
images 
37
.  
2.2 Characteristics of Ultrasonic Waves 
 Ultrasonic waves are high (?ultra?) frequency sound (?sonic?) waves. They 
vibrate at a frequency above 20,000 vibrations per second, or 20,000 Hz- too fast to be 
audible to humans. Our ear can detect frequencies between about 20 Hz (for example, the 
sound form a bumblebee?s wing) and 17 Khz (the sound from a whistle). Any sound at a 
higher frequency is ultrasonic and is inaudible.  
 INFRASOUND                                              SOUND                                      ULTRASOUND 
  
Figure 2.1: Acoustical Frequency Spectrum 
 
 Based on the frequency of ultrasound waves, applications can be divided into two 
groups: (1) applications which use low frequency ultrasound of order 200KHz to 20 
MHz, (used to diagnose the physical condition of the material) and (2) applications which 
use high frequency ultrasound of order 50MHz, (to act on a given material (therapy) to 
provoke a stimulus or a transformation in the material). Low frequency ultrasound 
utilizes only as much energy as needed to transmit a sufficiently clear signal through a 
material. By assessing the behavior and transformation of the wave in the medium, the 
condition and some characteristics of the material or specimen can be determined. 
 
   1 - 20 Hz                                  20 ? 20,000 Hz                          20000- ? Hz
  9 
 
Among the reasons that justify the use of high frequency waves for the evaluation 
of materials (instead of using audible frequencies) are: 
a) The absorption coefficients of waves at high frequencies are considerably high, thus 
their use in providing a sensitive parameter for evaluating variations in the internal 
condition of material.  
b) The small wavelength associated with the propagation of high frequencies make the 
ultrasonic testing sensitive to small heterogeneities along the wave path. Ultrasonic 
waves can detect heterogeneities equal to or larger than ?/2; therefore, higher 
frequencies make the testing sensitive to the presence of smaller singularities (e.g. 
defects, tiny tissues, air bubbles, and small particles, so on). 
Ultrasonic testing is accomplished by introducing electronically controlled pulses 
into a material from an external surface. The mechanical wave then travels within the 
material and manifests alterations (attenuation, reflection, scattering, change of 
propagation mode, etc) as it traverses variations in the mechanical composition (or 
impedance) in its path. The resulting reflected beam is captured by a transducer, and its 
features (amplitude, shape, time of flight, etc) are examined for evaluation of the physical 
characteristics and condition of the material. 
Some of the advantages of ultrasonics with respect to other NDT techniques are 
that defects may be detected in all kind of materials (metallic, nonmetallic, 
ferromagnetic, wood, ceramics, biomaterial, etc), and it can be also used to locate internal 
as well as superficial heterogeneities. Ultrasonic technique has rapid testing capabilities, 
and portable instrumentation is available for field and laboratory testing for a relatively 
low cost. Conversely, ultrasound is not exempt from limitations; certain physical and 
  10 
 
technological limitations restrict its use. There may be difficulty in coupling energy to 
rough surfaces, and it may be impractical to inspect complex shapes. Sometimes it is 
difficult to detect and measure the length of small, tight cracks or crack-like 
discontinuities. Also, rather extensive training is required for operators and data 
evaluators. The resolution of the test is subjected to the utilization of higher frequencies; 
however, as the frequency is increased, the damping of the wave increases as well. 
Therefore, a compromise has to be made between resolution and penetration depth.  
 
 
Figure 2.2: Relation between resolution and penetration depth 
Many advantages of ultrasonics have led to rapid development in its use. The 
disadvantages, however, may be formidable, and the diligent NDE engineer must ensure 
that ultrasonics is the proper technique selection for the required task 
13
. 
2.3 Basic Concepts 
 The presence of a medium - fluid or solid - is necessary for ultrasonic wave 
propagation. Wave propagation is the vibration or periodic displacement of successive 
elements of the medium. These low-energy vibrations (i.e., stress waves) can travel long 
distances in many liquids and solid materials as compared to travel in gases. 
  11 
 
Materials having elastic properties will carry ultrasonic waves as long as their 
elastic internal forces are capable of holding the particles within their equilibrium 
position. When the particles of a medium are displaced from their equilibrium positions, 
internal restoring forces arise. These elastic restoring forces between particles combined 
with the inertia of the particles, lead to oscillatory motion within the medium. 
Ultrasonic waves used for nondestructive testing are periodic and characterized by 
a central frequency ?f? expressed in cycle-per-second or Hertz [Hz]. The frequency 
corresponds to the number of oscillations that a particle experiences in one second, its 
inverse value is called period, denoted by ?T?, and is expressed in time units, see figure 
2.3. 
                                                         
f
T
1
=                                        (2.1) 
 
Figure 2.3: Harmonic Oscillation 
The phase velocity, ?c?, normally expressed in meters-per-second [m/s], is 
defined as the rate at which any particle amplitude of the perturbation propagates. This 
parameter is in general determined by the elastic properties of the materials; therefore it is 
a distinctive characteristic of each medium. If the material is homogeneous and isotropic, 
the phase velocity will be constant. Both parameters, frequency and phase velocity, are 
  12 
 
related by the wavelength ???, expressed in longitude units. It represents the least 
distance between identical particle displacements in the propagation medium, and is 
given by 
                                                              
f
c
=?                    (2.2) 
Sound travels through materials under the influence of sound pressure. Because 
molecules or atoms of a solid are bounded elastically to one another, the excess pressure 
results in a wave propagating through the solid. The resistance offered by the medium to 
the particle oscillation exposed to a perturbation is called Acoustical Impedance ?Z? 
[Kg/m
2
s]. A material having low impedance will offer slight resistance to deformations if 
an excitation acts on it and vice versa.  It is expressed as 
                                                cZ ?= ?                               (2.3) 
Where, ? is the material density. 
Acoustic impedance is important in: 
1. The determination of acoustic transmission and reflection at the boundary of two 
materials having different acoustic impedance. 
2. The design of ultrasonic transducers.  
3. Assessing absorption of sound in a medium. 
The normal force applied by a longitudinal wave on a specific surface of a particle plane 
within the material is called Acoustical Pressure ?P?, equation 2.4.  
  13 
 
If the wave has a shear propagation mode, it will apply a force parallel to the particle 
plane, then the pressure will be called shear stress. Both are expressed in Pascal [pa] or 
[N/m
2
]. 
                                                               cZP ?=                                  (2.4) 
2.4 Types of Ultrasonic Waves 
 
 The generation of ultrasonic waves can be done by any means that agitates liquids 
and gases or high-frequency displacements to surfaces of solid materials. Often, 
ultrasonic waves are generated using piezoelectric crystals and magnetostrictive 
materials. Other similar methods of wave generation use electromagnetic and 
electrostatic generators. Still other high frequency generators include whistle, mechanical 
vibrators, sirens, and thermal types such as high-energy laser pulses. 
 The major types of ultrasonic waves are longitudinal, transverse or shear, and 
surface or rayleigh waves. Most wave types are named according to relationships of 
particle motions relative to the direction of propagation of the ultrasonic beam 
13
. 
Longitudinal waves: In longitudinal wave mode, particles move parallel to the 
direction of wave propagation. The longitudinal wave mode is also called a pressure 
wave or P-wave, because the stress of the periodic compression and rarefaction of the 
particles is along the direction of propagation (Fig 2.4). 
 
Figure 2.4 - Longitudinal Wave 
  14 
 
Longitudinal waves can propagate in solids, liquids and gases and are most widely used 
for nondestructive testing of materials (Fig 2.5). 
 
Figure 2.5: Longitudinal wave propagation in a material 
 
Transverse or Shear Waves:  The transverse wave mode is often called a shear wave. In 
these, the particle motion will be perpendicular to the propagation of the wave (fig 2.6). 
Transverse wave inspection is usually limited to solids, since propagation in liquids 
occurs only in the very viscous types. Low-viscosity fluids, such as air or water, do not 
support shear stresses, and thus shear waves cannot propagate through air or water. 
 
 
Figure 2.6: Transverse or Shear Wave 
 
A shear wave penetration is normally achieved by using a longitudinal wave 
transducer attached to an acrylic wedge.  According to Snell?s Law, the proper selection 
  15 
 
of the angle of incidence of the beam will help propagate just transverse waves into the 
material, figure 2.7.  
 
Figure 2.7: Transverse or Shear Wave propagation in a material 
 
Surface Waves: These waves are also called Rayleigh waves. These waves propagate 
exclusively in the surface of materials to a depth of one wavelength.These waves have an 
elliptical particle motion in the vertical plane and normally travel undispersed on smooth 
surfaces (Fig 2.8).  
 
 
Figure 2.8: Surface Wave 
 
There are other kinds of surface waves known as lamb or plate waves. These are 
used when the plate in which waves travel is thin compared to the wavelength 
13
. 
  16 
 
Velocities of the various wave types are determined by modulus, density, and 
Poisson?s ratio of the material in which they propagate. Each type of wave has a different 
phase velocity, and in each case it depends on the elastic properties of the material and 
the relative size of the object. The propagation speed or phase velocity of longitudinal 
(c
L
), transverse (c
T
), and surface (c
s
) waves can respectively be expressed as 
 
)21)(1(
)1(
???
?
?+
?
=
E
c
L
      (2.5) 
 
???
GE
c
T
=
+
=
)1(2
     (2.6) 
 
)1(21
22.187.0
???
?
+
?
+
+
=
E
c
s
 (2.7) 
 
where ?E? stands for Young's modulus, ?G? is the Shear Modulus, ??? is the Poisson?s 
Coefficient and ??? is the density of the propagation material 
By relating the first two equations, an expression is found that associates the 
longitudinal wave velocity with the transverse wave velocity. This is: 
 
)1(2
21
?
?
?
?
=
LT
cc          (2.8) 
 
  17 
 
Table 2.1 illustrates the density, longitudinal and transverse wave velocity, and the 
acoustic impedance of some materials and substances. 
 
VELOCITY 
[km/s] 
 
MATERIAL 
 
DENSITY 
[g/cm
3
] 
c
L 
c
T 
 
ACOUSTIC 
IMPEDANCE 
Z=??c
L    
 
[Kg/m
2
s]
 
?10
6 
Steel (structural steel) 
7.85 5.82 3.19 45.7 
Steel 1018  (Reference Block) 
7.85 5.92 3.25 46.4 
Aluminum 
2.71 6.32 3.08 17.1 
Alloy Al-Cu = AI L3120 
2.78 6.25 3.10 17.4 
Iron Cast 
7.2 3.5-5.6 2.2-3.2 25-40 
Iron Electrolytic 
7.9 5.95 3.22 45 
Inconel  
8.25 7.82 3.02 64.5 
Cooper 
8.9 4.7 2.26 41.8 
Gold 
19.3 3.24 1.20 6.25 
Platinum 
21.4 3.96 1.67 8.47 
Nickel 
8.9 5.63 2.96 50 
Silver 
10.5 3.60 1.59 3.78 
Lead 6% antimony 
10.90 2.16 0.81 23.6 
Brass 
8.1 2.12 4.43 35.8 
Plexiglas (PMMA, Perspex) 
1.18 2.73 1.43 3.2 
Zinc 
7.1 4.17 2.41 29.6 
Araldite 
1.15-1.3 2.5-2.8 1.1 2.8-3.7 
Quartz Glass 
2.60 5.57 3.51 14.4 
Rubber (vulcan) 
1.2 2.30  2.8 
Lithium Sulfate (Li
2
SO
4
) 
2.06 4.72 8.6 
Teflon 
2.2 1.35  3.0 
Oil (SAE 20 a30) 
0.89-0.96 1.74 1.5-1.7 
Bone 
1.62 2.5-4.7 4-7.5 
Water 
1 1.48 1.48 
Blood 
1.06 1.57 1.66 
Muscle 
1.07 1.59 1.7 
Fat 
0.92 1.45 1.33 
Glycerin 
1.26 1.92 2.4 
Air 
0.0012 0.330 
 
0.389?10
-3 
 
Table 2.1: Wave speed, density, and acoustic impedance for some materials 
 
  18 
 
2.5 Behavior of Ultrasonic Waves at Boundaries 
 
 The reflection and refraction of the wave front at the boundaries or interface plays 
an important role in ultrasonic investigations.  Voids, cracks, inclusions and coatings can 
be determined using this effect. Deviation of, or changes in, the wave as it encounters an 
interface or boundary can lead to one of the following: 
? Reflection and/or transmission of the wave 
? Propagation of the wave along the boundary or interface 
? Change in direction of wave travel (refraction) 
? Conversion from one type of wave to another type of wave (mode conversion) 
To understand the behavior of the ultrasonic waves at the boundary, we need to 
understand the: 
1) Normal Incidence  
2) Oblique Incidence 
Here we will discuss only the normal incidence because in our application we 
deal with the normal incidence of ultrasonic waves on the spinous process of the human 
vertebra. In normal incidence, a propagating plane wave impinges at 90
o
 onto a smooth 
surface separating mediums 1 & 2.  
When an ultrasonic beam reaches a smooth boundary one then speaks of 
reflection; on the other hand, if the reached boundary is rough, i.e. it has irregularities, 
then the beam gets scattered. In this connection the roughness of the boundary is 
measured in terms of the wavelength size. When another material is behind the boundary 
and adherences to the first material so that forces can be transmitted, then the wave may 
propagate on it. 
  19 
 
 
Figure 2.9: Normal incidence of an ultrasonic wave on a smooth boundary 
 
Let?s now consider the simple case of a plane wave striking at right angle a plane 
of smooth boundary that divides two different materials, figure 2.9. A Portion of the 
wave energy is transmitted to the second medium characterized by an acoustic impedance 
Z
2
 and the remainder is reflected back within the incident medium characterized by an 
acoustic impedance Z
1
. Both waves propagate in a right angle with respect to the 
boundary.  
 We now define the Reflection coefficient ?R? as the ratio between the reflected 
acoustic pressure P
r
 and the acoustic incident pressure P
0. 
The Transmission coefficient 
?T? is also defined as the ratio between the acoustic transmitted pressure P
t
 and the 
acoustic incident pressure P
0
. Both values are dimensionless. 
                                                  
0
P
P
R
r
=    And 
0
P
P
T
t
=            (2.9) 
By using the relation between acoustic pressure and acoustic impedance, Eq. 2.4, we 
arrive at 
                                                      
12
12
ZZ
ZZ
R
+
?
=                                (2.10) 
  20 
 
                                                     
21
2
2
ZZ
Z
T
+
=                                (2.11) 
From equation 2.10 and table 2.1 it can be inferred that the absolute value of 
reflection coefficient R tends to 1 (most of the energy is reflected back) when one of the 
mediums is air. This is a result of the low acoustical impedance of air compared with any 
other solid or liquid. If the acoustic impedance of the first medium is greater than the 
second medium, the reflection coefficient will take a negative value. This fact associates 
a shifting in the phase of the reflected wave with respect to the incident wave. As a 
consequence, it is concluded that the reflection coefficient is affected by the side where 
the wave strikes the interface. On the other hand, if the incident wave comes from the 
medium of less acoustic impedance, then the transmission coefficient will have a value 
greater than 1. Taking the impedance of PMMA (Plexiglas) Z
p
 and Aluminum Z
a
 as an 
example, and having PMMA as the incident medium, the coefficients R and T can be 
calculated as: 
7.1
172.3
17*2
,68.0
2.317
2.317
=
+
==
+
?
= TR         (e - 2.1) 
The transmitted wave has 170% the sound pressure of the incident wave. That is, the 
incident sound pressure is amplified in the second medium.  
As a second example, consider the propagation from human soft tissue (muscle) 
Z
s 
= 1.6?10
6 
[kg/m
2
s], and hard bone Z
b 
= 7.5?10
6 
[kg/m
2
s], then R and T result in: 
63.1
7.15.7
5.72
,63.0
7.15.7
7.15.7
=
+
?
==
+
?
= TR  (e-2.2) 
 These results confirm the stress (pressure) relation at the boundary  
                                      P
o
 + P
r
 = P
t        
 or        1 + R = T                    (2.12) 
  21 
 
The energy balance expressed in terms of intensities, calculated on a given boundary for 
a normal incidence furnishes: 
I
0 
= I
r
 + I
t
                                (2.13) 
The expressions for the reflection and transmission coefficients are also valid for 
transverse waves. However, transverse waves are completely reflected from an interface 
solid-gas or liquid since shear waves in general do not propagate in these substances 
12
. 
 Power ratios are very important in ultrasonic inspection. The power expressions 
yield the rate at which energy is being transmitted by the wave front. Generally, power 
can be calculated by: 
               Pwr = Stress * Velocity at a point                        (2.14) 
In a similar manner, power expressions for the incident, transmitted, and reflected 
waves are: 
                                                        
1
22
2
1
C
EA
Pwr
i
i
?
=                              (2.15) 
        
22
1
''
2
1
?? t
t
ACPwr =                         (2.16) 
                                                        
22
1
2
1
?? r
r
ACPwr =                           (2.17) 
Power transmission and reflection ratios can be obtained by algebraic 
manipulation, using the particle displacement: 
                                    
2
12
12
/1
/1
?
?
?
?
?
?
+
?
=
ZZ
ZZ
Pwr
Pwr
i
t
                                 (2.18) 
                                                    
[ ]
[]
2
12
12
/1
/4
ZZ
ZZ
Pwr
Pwr
i
r
+
=                                 (2.19) 
  22 
 
The behavior of both the pressure and the power at the boundary are important in 
nondestructive inspection 
14
. 
2.6 Attenuation of Ultrasonic Waves 
 
 The behavior of an acoustic wave to lose energy when traveling through materials 
is known as attenuation. Attenuation of the waves occurs due to the following 
mechanisms: 
? Absorption: dissipation of energy in the form of heat. 
? Scattering: diffraction, reflection, and refraction of the ultrasonic wave due to 
discontinuities in the medium or at the surface of the medium. 
? Beam Spreading: geometric expansion of a nonplanar wave front. 
? Dispersion: Difference of velocities of different wave modes 
12
. 
Attenuation is usually expressed in the following form 
    
aL
ePP
?
=
0
                                        (2.20)      
Where 
 
0
P = Original pressure level at a source or other reference location. 
 P= Pressure level at second reference location 
 a = Attenuation coefficient (Nepers per cm) 
 L= Distance of pulse travel form original source to second reference location. 
Ultrasonic pulse attenuation is expressed in units of decibels (dB). This a convenient unit 
to use when the magnitude of the parameter being measured varies over a large range. 
Generally, these decibels are based on a logarithmic scale. 
  23 
 
The relative sound pressure level (SPL) of a propagating wave is 
            dB
P
P
SPL
0
log20=                                               (2.21) 
Where, 
 P = Effective Pressure of ultrasonic wave at observation point 
 P
0
= Pressure at an earlier reference point. 
 
If we consider two points in the ultrasonic wave path, then the sound pressure level loss 
for an ultrasonic wave passing between 1 & 2 is given by 
                                        dB
P
P
SPLSPL
2
1
21
log20=?                                    (2.22) 
 
If the stations are separated by a distance L and the material has attenuation 
coefficient? , the above equation can be rewritten as  
                                           dB
P
P
L
2
1
log20=?                                                 (2.23) 
Here L is the length and is generally expressed in meters. So, the units of ?  will be in 
decibels per meter 
14
.  
  24 
 
The attenuation coefficient increases with increasing frequency. The table below gives 
the attenuation coefficients for soft tissue. 
Frequency (MHz) Average Attenuation Coefficient for 
Soft Tissue (dB/cm) 
1.00 0.5 
2.25 1.1 
3.50 1.8 
5.00 2.5 
7.50 3.8 
10.00 5.0 
 
Table 2.2: Average Attenuation Coefficients for soft tissue 
 
A simple proportional approximation is that soft tissue, on average, has 0.5 dB of 
attenuation per centimeter for each megahertz of frequency 
15
. 
 
 
 
 
 
 
  25 
 
 
 
3. TESTING TECHNIQUES AND DATA PRESENTATION FOR ULTRASONIC 
TESTING 
 
3.1 Introduction 
 
Ultrasonic testing uses high frequency sound energy waves to conduct examinations 
and make measurements. Ultrasonic inspection can be used for flaw detection/evaluation, 
dimensional measurements, and material characterization, among other things.  
The propagation of the ultrasonic waves in a material depends on the elastic 
properties of the material and also on the homogeneity of the material?s structure. The 
direction of the waves and measurement of time taken for the waves to pass through the 
material or reflect from the back surface or defects is very important in the ultrasonic 
inspection. 
A typical UT inspection system consists of several functional units, such as the 
pulser/receiver, transducer, and display devices. There are two kinds of testing 
techniques, which are normally used for inspection. They are: 
1) Pulse Echo Technique 
2) Through Transmission Technique 
Our research project deals with pulse echo technique. We image the spinous process 
of the human lumbar vertebra from the waves reflected back from spinous process tips. 
3.2 Pulse Echo Technique:  
 
       Pulse Echo technique is also known as the pulse transit-time method. This 
method has been in use since World War I for locating objects under water. The principle 
  26 
 
of the pulse echo technique is the simplest of all the ultrasonic testing methods and it is 
one of the most commonly used techniques.  
In this technique a piezoelectric element excited by an extremely short electrical 
discharge transmits an ultrasonic pulse into a specimen. The probes (emitter-receiver) are 
coupled to the surface of the test object by a liquid or coupling paste so that the sound 
waves can transmit into the specimen from the emitter probe and from the specimen into 
the receiver probe. In some cases, a single transducer acts as both the transmitter and 
receiver, as shown in fig 3.1. If any flaw is found in its path then it reflects back an echo 
that is captured by the receiver probe. Another echo is reflected from the back wall but 
with a certain delay in respect to the first reflection. Observation of the received pulses 
can provide valuable information about the nature of the defect from which the pulses 
have been reflected and, perhaps, of the structure of the material being tested. 
 
 
Figure 3.1: Basic schematic of pulse-echo testing technique. In the instrument screen we 
can see all the echoes received (i.e. back wall, crack echo and initial pulse) 
 
If we know the velocity of the sound in the object, then the time of flight of the 
pulse obtained from the oscilloscope can be converted into distance or depth in the 
Plate
Crack
0 2 4 6 8 10
Initial  
 pulse 
Crack 
   Echo 
Back surface 
   Echo 
  27 
 
object. The intensity and shape of the reflected beam depend mainly on the material, 
attenuation, size of the reflector, frequency of the ultrasonic wave, location of the 
reflector within the object, defect orientation in respect to the axis of the beam, etc. 
 The main advantage of this method is that access from only one side of the object 
is necessary, provided that the back surface of the object is parallel to the surface where 
the transducer is placed. 
3.2.1 Design of Pulse Echo Equipment 
 The figure 3.2 shows the basic design of the pulse echo method equipment. This 
is commonly known as the ultrasonic flaw detector, but it can be employed for many 
other applications. With the aid of this equipment, a trigger can excite simultaneously a 
time-base control and a pulse generator at regular intervals, usually between 50 and 1000 
Hz. Once excited, the time-base control connected to the X-plates of the cathode ray 
oscilloscope causes the electron beam to sweep in a horizontal direction from left to right. 
We can use the range control device to vary the time of sweep so that it suites the 
acoustic path length. A multi-position switch can be used to extend the range of this 
continuous variation in time of sweep by several orders of magnitude. At the end of the 
sweep, the electron beam returns to its original position for the next excitation of the 
trigger. When there is no signal applied to the Y-plate, a bright horizontal trace appears 
on the oscilloscope screen. 
 Once excited by the trigger, the pulse generator feeds a direct potential difference, 
usually from several hundred to thousand volts and for an instantaneous duration to the 
electrodes of either a transmitting or reversible probe in contact with the material under 
the test. Pulse energy control can be used to adjust the magnitude of this applied voltage. 
  28 
 
 A reversible probe is used for a single probe operation and this is connected to an 
amplifier and rectifier, which can be bypassed if a display of the waveform is required, to 
the Y-plates of the oscilloscope. The output of the amplifier is usually adjusted by using a 
sensitivity control. When the probe receives the shock excitation, it generates an 
ultrasonic pulse, and a large peak known as transmission peak appears at the left-hand 
extremity on the oscilloscope screen. Returning echoes received by the probe after 
reflections are converted into electronic pulses and the corresponding peaks appear on the 
oscilloscope screen.  
 
Figure 3.2: Basic Design of Pulse Echo Technique 
 
In a double probe operation the transmitting probe is not directly connected to the 
oscilloscope; therefore, on transmission of the pulse, the transmission peak does not 
appear on the oscilloscope screen. However, the received echoes are picked up by the 
  29 
 
receiving probe and they are converted into electrical pulses and are fed to the Y-plates of 
the oscilloscope similar to the single probe operation 
16
. 
In the time taken for the sound pulses to travel through the delay, the echo peaks 
are displaced to the right of point A by distances corresponding to the amount of the 
delay. Peaks B and C correspond to the first back wall echo and internal defect. Because 
of the rapidity of the pulse generation as determined by the pulse repetition frequency 
(PRF), the displayed peaks appear to be steady. The time delay values can be determined 
by calibrating the time base. If we assume that the time base indications vary linearly 
with the horizontal distance, then the distance of the indicated defect from the front 
surface of the test object is equal to the product of its thickness and the ratio AC/AB 
16
. 
3.3 Through Transmission Technique 
 
Through-transmission is used in several cases, particularly for highly attenuate 
material where a pulse-echo results in significant loss in signal strength. In this technique 
the transmitter probe is placed on one side of a specimen and a receiver on the opposite 
side and the specimen is scanned across as shown in figure 3.3, any variations in 
ultrasonic attenuation in the specimen will be registered.  
 
Figure 3.3: Schematic of Through Transmission Technique 
 
T R
T R
1
1 
2 
0 24 6 8 1
2
1
1
  30 
 
An internal flaw in the specimen will reduce the intensity of the transmitted 
ultrasonic energy as it comes between the probes. Usually this technique is difficult to 
apply, as the two probes must be maintained rigidly at a fixed distance and angle. Any 
probe movements relative to one another, or any variation in the specimen surface, will 
cause a change in the transmitted intensity. This method is sometimes called a Pitch-
Catch method or obscuration technique. Through transmission is useful in detecting 
discontinuities that are not good reflectors and when signal strength is weak. This 
technique does not provide the depth information of the crack. 
3.4 Data Presentation 
There are several ways in which the information delivered to the display may be 
represented. Each presentation mode provides a different way of looking at and 
evaluating the area of material being inspected. There are four different types of scans or 
presentation modes in practice. They are  
1) A mode scan or amplitude mode scan  
2)  B mode scan or brightness mode scan 
3) C mode scan 
4) M mode scan or motion mode scan 
3.4.1 A-Scan Presentation 
The A mode scan or simply A-scan displays the amount of received ultrasonic energy as 
a function of time. A mode operation causes a vertical deflection of the spot each time a 
pulse i.e., reflection, is received by the transducer. The relative amount of received 
energy is plotted along the vertical axis and elapsed time (which may be related to the 
sound energy travel time within the material) is display along the horizontal axis. In the 
  31 
 
A-scan presentation, relative discontinuity size can be estimated by comparing the signal 
amplitude obtained from an unknown reflector to that from a known reflector. Reflector 
depth can be determined by the position of the signal on the horizontal sweep. 
 
 
 
 
 
 
 
 
                              Figure 3.4: Scanning Procedure of the Specimen 
In the A-scan presentation shown in figure 3.5, the initial pulse generated by the 
transducer is represented by the signal IP, which is near time zero. As the transducer is 
moved along the surface of the part as shown in figure 3.4, four other signals will appear 
on the screen at different times. When the transducer is at the extreme left position, we 
will see two signals i.e. the IP signal and signal A (the sound energy reflecting from 
surface A) will be seen on the trace. As the transducer is scanned to the right, a signal 
from the back wall BW will appear on the screen showing that the sound has traveled 
farther to reach this surface. When the transducer is over flaw B, signal B, will appear at a 
point on the time scale that is approximately halfway between the IP signal and the BW 
signal. Since the IP signal corresponds to the front surface of the material, this indicates 
  32 
 
that flaw B is about halfway between the front and back surfaces of the sample. When the 
transducer is moved over flaw C, signal C will appear earlier in time since the sound 
travel path is shorter, and signal B will disappear since sound will no longer be reflecting 
from it 
16
. 
 
Figure 3.5: A-scan Presentation 
3.4.2 B-Scan Presentation 
The B-scan presentation as shown in figure 3.6 is a cross-sectional view of the 
test specimen. In the B-scan, the time-of-flight (travel time) of the sound energy is 
displayed along the vertical, and the linear position of the transducer is displayed along 
the horizontal axis. From the B-scan, the depth of the reflector and its approximate linear 
dimensions in the scan direction can be determined. The B-scan is typically produced by 
establishing a trigger gate on the A-scan. Whenever the signal intensity is great enough to 
trigger the gate, a point is produced on the B-scan. The gate is triggered by the sound 
reflecting from the back wall of the specimen and by smaller reflectors within the 
material. In the B-scan image above, line A is produced as the transducer is scanned over 
  33 
 
the reduced thickness portion of the specimen. When the transducer moves to the right of 
this section, the back wall line BW is produced. When the transducer is over flaws B and 
C, lines that are similar to the length of the flaws and at similar depths within the material 
appear in the B-scan. A limitation to this display technique is that reflectors may be 
masked by larger reflectors near the surface 
37
. 
 
Figure 3.6: B-Scan Presentation 
3.4.3 C-Scan Presentation 
The C-scan presentation provides a plan-type view of the location and size of test 
specimen features, as shown in figure 3.7. The plane of the image is parallel to the scan 
pattern of the transducer. C-scan presentations are produced with an automated data 
acquisition system, such as a computer controlled immersion scanning system. Typically, 
a data collection gate is established on the A-scan and the amplitude or the time-of-flight 
of the signal is recorded at regular intervals as the transducer is scanned over the test 
piece. The relative signal amplitude or the time-of-flight is displayed as a shade of gray 
or a color for each of the positions where data was recorded. The C-scan presentation 
  34 
 
provides an image of the features that reflect and scatter the sound within and on the 
surfaces of the test piece. High resolution scan can produce very detailed images 
37
.  
 
 
                                                                                            
 
 
 
 
 
 
 
 
Figure 3.7: C-Scan Presentation 
 
3.4.4 M-Scan Presentation:  
 M-scan is similar to a B scan presentation, in which the motion of the spots is 
recorded by a recording medium, usually a strip chart recorder that moves across the face 
of the display. This results in a recording of the reflector motion. The M-mode scanning 
is generally used in heart studies. 
 
  35 
 
 
 
4. ULTRASONIC TRANSDUCERS 
 
4.1 Introduction 
 
A transducer is a device that converts one form of energy to another, for example, 
electrical energy to ultrasonic energy or vice versa. Most of the ultrasonic transducers are 
reversible: the energy conversion is possible in both directions with equal efficiencies.  
Ultrasonic transducers may be classified as follows: 
1) Piezoelectric transducers 
2) Electromagnetic transducers 
3) Electrostatic transducers 
4) Magnetostrictive transducers 
5) Laser and other Optical transducers 
Quality of performance, ease of application and cost are the important 
considerations in selecting the transducers. Piezoelectric transducers are widely used for 
various inspection processes. However, for proper transmission of ultrasonic waves in the 
object under test we need a coupling medium which can satisfactorily transmit the 
ultrasonic waves. 
4.2 Construction of a Simple Ultrasonic Transducer: 
 
Three major elements in any ultrasonic transducer construction are: active element, 
backing and wear plate.  
Active element: The active element, normally a piezoelectric material, converts electrical 
energy such as an excitation pulse into ultrasonic mechanical energy and vice versa. The 
  36 
 
most commonly used materials are natural piezoelectric as well as polarized ceramics 
(polycrystalline) such as quartz, barium titanate, lithium sulfate and lead meta-niobate. 
The active plate is normally 1/2 wavelength thick. 
Backing: The backing is usually a highly attenuate material that is used to control the 
vibration of the transducer by absorbing the energy radiated from the back face of the 
oscillator. When the acoustic impedance of the backing matches the acoustic impedance 
of the oscillator, the back face of the oscillator transmits a great portion of its vibration 
into the damping body. As a result, the vibration is absorbed by the backing material, and 
the vibration of the plate is stopped. This condition describes a heavily damped 
transducer that displays short pulses (good resolution) but low signal amplitude. On the 
contrary, if there is a mismatching in acoustic impedance between these two materials, 
more energy will be reflected forward into the specimen. This is the case of a bad 
resolution transducer due to the longer wave duration, but may be higher in signal 
amplitude or sensitivity. Materials such as vulcanized rubber and molded fiber plastic are 
satisfactory for moderate demands at high frequencies. Composite materials based on 
curable synthetic resins or rubbers in which other powdery mixtures have been 
incorporated are preferable. Attempts have also been made to scatter and disturb the 
waves by using cellular structures and oblique or saw-tooth shaped end faces 
respectively. Such means can be applied successfully only in combination with an 
intrinsically effective absorption. Otherwise, the various interfering echoes will produce a 
background of grass behind the transmitting pulse.  
Wear Plate: The wear plate?s purpose is to protect the oscillator plate from the testing 
environment. In the case of contact transducers, the wear plate must be durable and 
  37 
 
corrosion resistant in order to withstand the wear caused by the abrasion of the specimen 
surface. For immersion, angle-beam and delay-line transducers the wear plate has the 
additional purpose of serving as an acoustic impedance adaptor between the active 
element and the water, wedge or the delay line respectively 
39
.  
4.3 Principle of Operation 
 
Transducers operating by the principle of piezoelectric effect or magnetostrictive 
effect are used for producing ultrasonic sound. High intensity ultrasonic sound of 
frequency 20-40 kHz range can be produced by using magnetostrictive transducers. The 
high intensity sound of frequency 20-40 kHz is used in ultrasonic cleaning and other 
mechanical applications. Ultrasound of frequency 1-20MHz is produced by introducing 
the output of an electronic oscillator to a thin wafer or piezoelectric material like lead 
zirconate titanate. This type of ultrasound is used in ultrasonic medical imaging. The 
higher frequencies have shorter wavelengths and thereby provide higher resolution to the 
imaging process 
39
. 
4.4 Resolution & Sensitivity of Ultrasonic Transducers 
 
Characteristics of an ultrasonic testing system are mainly dependent on the 
transducer?s features like resolution and sensitivity.  
There are two types of resolution, Axial resolution is the ability of the probe to 
produce simultaneous and distinct indications from reflectors located at nearly the same 
position with respect to the sound beam. In other words, the minimum distance in the 
beam direction between two reflectors can be identified as separate echoes. Axial 
resolution is slightly more than half the spatial pulse length, SPL, defined as the product 
between wavelength and the number of cycles in the pulse. Thus, the axial resolution can 
  38 
 
be improved in two ways: 1) decreasing the number of cycles in each pulse by 
manipulating the transducer damping, and 2) decreasing the wavelength of the pulse.  
The number of cycles per pulse can typically be reduced to a minimum of one.  
Typically, a frequency range of 2 to 10 MHz is used to meet both resolution and imaging 
depth requirements. The reason why the minimum reflector distance must be larger than 
half the spatial pulse length is shown in figure 4.1.  
 
Figure 4.1: Axial Resolution Effect 
 
An ultrasonic transducer and its ultrasound pulse are analyzed at four different 
times. At time 1, the transducer has just emitted an ultrasound pulse with a spatial pulse 
length SPL as indicated by the length of the arrow. The pulse encounters two reflectors, 
R1 and R2, separated by a distance exactly equal to 1/2 SPL in the ultrasound beam 
direction. At time 2, part of the pulse is reflected from R1; the remainder of the pulse 
travels on. At time 3, part of the pulse is also reflected from R2. The echoes from R1 and 
R2 both have lengths equal to the pulse length (SPL). As the "tail" of the echo from R1 
leaves this reflector, the "head" of the echo from R2 reaches R1 (time 3). At time 4, both 
echoes are seen propagating towards the transducer, the "head" of the last echo "biting 
the tail" of the first one. The transducer therefore cannot separate the echoes. For the two 
  39 
 
echoes to be resolved, the distance between the reflectors needs to be slightly longer than 
half the spatial pulse length, which is the maximum axial resolution.  
Lateral Resolution refers to the ability to discern two separate objects 
perpendicular to the ultrasound beam direction. For a single-element transducer, lateral 
resolution is determined by the ultrasound beam diameter. In order to separate two 
objects that are closely spaced, the beam must be narrower than the space between them. 
As the diameter of the beam varies with distance from the transducer so does the lateral 
resolution. The primary mean to reduce the beam diameter is focusing the beam. Lateral 
resolution is directly proportional to the frequency, but there always exists the limitation 
of attenuation as one goes higher in frequency. 
Sensitivity: This is the ability of an ultrasonic probe to detect reflectors at a given depth 
in a test material. The greater the signal that is received from these reflectors, the more 
sensitive the transducer is. It is a measure of the test system?s ability to detect 
discontinuities producing relatively low-amplitude signals because of their size, 
geometry, or distance.   
 
 
 
Table 4.1: Effect of axial resolution, lateral resolution and penetration of the ultrasonic 
beam as a function of the frequency 
 
Table 4.1 summarizes the effect of axial resolution, lateral resolution and sensitivity of 
ultrasonic transducers as a function of frequency.  
 2.0MHz 5.0MHz 
Axial Resolution Decrease Increase 
Lateral Resolution Decrease Increase 
Sensitivity Increase Decrease 
  40 
 
The variety of transducers used for ultrasonic testing is divided in two main types 
based on type of waves that they propagate. They are 1) normal incidence or longitudinal 
wave transducers and 2) angular incidence or transverse wave transducers 
17, 18
.  
4.5 Piezoelectric Transducers 
 
Piezoelectric transducers are the most commonly used for detecting and creating 
ultrasonic waves. The piezoelectric effect was discovered by Jacques and Pierre Curie in 
1880. The piezoelectric effect is the characteristic of single crystals of certain insulators, 
including lithium sulphate and quartz, and some semiconductors such as zinc oxide and 
cadmium sulphide. The piezoelectric effect requires the presence of a polar axis, which is 
present naturally in the single crystal materials used as transducers. When we have a disc 
made from one of these materials having a polar axis perpendicular to the flat parallel 
surfaces and subject it to mechanical stress, equal and opposite electric charges appear on 
these surfaces. This is called as the direct piezoelectric effect.  
We can categorize the piezoelectric transducers by the beam orientation, by the 
environment where it is used, and by the type of wave generated. Most common 
classifications are: 
1) Type of waves generated (longitudinal, shear or surface) 
2) Contact, immersion, or air-coupled 
3) Normal or angled beam 
4) Broadband or narrowband 
5) Single or multiple elements 
6) Transducer face ? flat (normal) or shaped (contoured or focused) 
7) Ambient or high temperature 
  41 
 
We are next going to discuss about the contact, immersion, normal or angle 
beamed and single or multiple elements transducers, as these are most directly related to 
the research work here presented. 
4.5.1 Contact, Immersion or Air-Coupled Transducers 
 
 Piezoelectric transducers are also classified by their coupling mechanisms: 
contact, immersion, or air-coupled. Contact transducers, although they appear to come 
into direct contact with the object under test, in fact require some form of dry couplant or 
liquid to adequately couple the ultrasound to and from the object under test. A couplant is 
generally necessary because of the acoustic impedance mismatch between air and solids; 
for example the test specimen is large and, therefore, nearly all of the energy is reflected 
and very little is transmitted into the test material. The couplant displaces the air and 
makes it possible to get more sound energy into the test specimen so that a usable 
ultrasonic signal can be obtained. There also exist those transducers that transmit the 
ultrasonic energy normally to the contact surface but use a liquid medium as vehicle; 
these transducers are known as immersion transducers.  
Immersion transducers operate in a scanning tank where the specimen and the 
transducer are fully immersed within the fluid (typically water). Immersion transducers 
have a design similar to that of contact transducers but the wear plate in its case works as 
an impedance adapter and are designed to match the acoustic impedance of water 
37, 17
.
  
It offers two mayor advantages over the contact transducer: 
? Uniform coupling which reduces variation in the sensitivity. 
? The focusing feature increases the sensitivity to small reflector. 
  42 
 
There are three basic configurations: unfocused (flat), spherical focused (spot), 
and cylindrical focused (line), figure 4.2. In most transducers the focusing is 
accomplished by the addition of a lens on the end of the oscillator. A spherical focus 
beam is normally used to improve sensitivity to small discontinuities while a cylindrical 
focus is used for inspection of pipes or bars.  
The focal length is the distance from the face of the transducer to the point in the 
sound field where the signal has maximum amplitude. In the case of spherical focus, the 
focal length depends upon the spherical radius of the lens, as well as the size and 
frequency of the element. A small radius produces shorter focal length. The same applies 
for cylindrical lenses.  
 
Figure 4.2: Cylindrically and spherically focused transducers 
 
At or near the theoretical focus area, the sound beam maintains shape within a 
short zone before it again diverges and rapidly spreads out. Since the last signal 
maximum occurs at a distance equivalent to the near field, a transducer cannot be 
acoustically focused at a distance greater than N (near field length). The maximum 
practical focal length for a point target is 0.8N.  
  43 
 
The measured focal length of a focused transducer depends on the material in 
which it was measured. When specifying a transducer focal length, it typically refers to 
water. Since most of the materials have a higher propagation velocity than water, the 
focal length is effectively shorter as justified by Snell?s Law. The focal length is also 
affected by the curvature of the surface of the test piece 
37, 18
.  
Because of the high impedance mismatch between the air and the piezoelectric 
crystal, these air-coupled transducers require a special layer of material for sending the 
pulse through air to the sample. This layer is called as the impedance matching layer 
12
. 
4.5.2 Normal or Angled Beam Transducers 
 
Transducers can also be categorized on the way the ultrasonic waves transmit 
from the face of the transducer as normal beam or angled beam. Normal beam 
transducers, as shown in figure 4.3-a, transmit a wave normal to the face of the 
transducer, whereas angled beam transducers transmit a wave at an angle (not normal) to 
the face of the transducer. Angled beam transducers are usually just the normal beam 
transducers attached with a wedge, as shown in figure 4.3-b, often made of plastic. An 
important point to be remembered is, due to the Snell?s Law, the angle in the wedge is 
not the same as the angle of the beam created in the sample. When angled beam 
transducers are manufactured, manufacturers label their transducers based on the angle of 
injection.  
  44 
 
 
Figure 4.3 - a) Normal Beam Transducers b) Angled Beam Transducers 
4.5.3 Single and Multiple Element Transducers 
 
If the transducer has a single element then it is called a single element transducer. 
The single element of crystal acts as both the transmitter and receiver. The elements of a 
single crystal transducer are shown in figure 4.4.  The external housing is the support of 
the other elements. The inner sleeve isolates the active (piezoelectric element) element 
and the backing from the external house. Electrodes attach to both surfaces of the active 
element and transfer the electric charges to the active element and from the active 
element to the electrical leads or cables. The electrical network consists in passive 
elements that work as an impedance matching between the pulse transmitter and the 
active element. The other three elements, backing, active element, and wear plate, 
discussed earlier, are the most critical in the design of the transducer. 
 
Figure 4.4: Components of a single element transducer 
  45 
 
 
Piezoelectric transducers commonly contain multiple (two or more) elements. In 
the dual element transducers, we have separate transmitter and receiver elements housed 
in a common case, as shown in figure 4.5. One of the elements transmits and the other 
receives. Active elements can be chosen for their sending and receiving capabilities 
providing a transducer with a cleaner signal, and transducers for special applications, 
such as inspection of course grain material. Dual element transducers are especially well 
suited for making measurements in applications where reflectors are very near the 
transducer since this design eliminates the ring down effect that single-element 
transducers can produce. (When single-element transducers are operating in pulse echo 
mode, the element can not start receiving reflected signals until the element has stopped 
ringing from its transmit function.)  
 
Figure 4.5: Components of a Dual Element Transducer 
 
Dual element transducers are very useful when making thickness measurements 
of thin materials and when inspecting for near surface defects. The two elements are 
angled towards each other to create a crossed-beam sound path in the test material. This 
kind of arrangement allows for improvement in the near surface resolution 
12, 37
. 
  46 
 
 A set of several normal piezoelectric transducers acting together is called an 
array. If the transducers are driven at slightly different times by either electrical or 
physical means, so that the individual waves interfere constructively and destructively 
into an angled wave, this is called a phased array. The individual transducers in phased 
array transducers are usually as small as possible, so that the individual elements appear 
as point sources.  
The phased array concept deals with multi element transducers. Each element of 
these transducers is connected to a different electronic channel, either directly or through 
multiplexers, according to electronic device performances. Each element can be activated 
or not for each shot. The activated elements give the size and the location of the active 
aperture of a phased array transducer. An electronic delay can be applied to each 
electronic channel when emitting and receiving the signal to/from the transducer 
elements. The setup corresponding to all the delays of a given shot is called Delay Law. 
Each delay law defines a different acoustic beam with particular direction, focusing 
distance and lateral resolution. This technique requires probes with very low acoustic and 
electric cross coupling between the elements, so that all the elements can be fired 
independently 
40
. 
All elements are connected to, and controlled by, a computerized ultrasound 
system. The system is able to activate each element independently. Typical element size 
is from 0.02? to 0.1?. Also available are annular arrays, which are circular pieces, divided 
into donut shaped annular elements. Timing or phasing the individual elements 
appropriately can be utilized to create different beam profiles. Such is the versatility that 
the beam can be focused or steered in a wide range of angles.  
  47 
 
 
 
Figure 4.6: Electronic phasing used to steer a sound field 
 
A steered angle beam is created by sequentially firing each element in an array to 
create a wave front following the desired angle, figure 4.6. The angle is set electronically 
by the instrumentation, and can if necessary be changed pulse by pulse.  
The advantages are: 
? Only one transducer is required for inspection at variable angle. 
? Fast inspection of complex geometry parts. 
? The advantage of this technique can be combined with the advantages of 
electronic focusing. 
The creation of a focused beam is achieved by a different pulsing cadence, i.e. by 
selecting the firing order and pulse delays of the array elements. This can be changed 
pulse by pulse to sweep a focal point through a range of depths in the test material, 
(Figure 4.7). Note that the beam steering and dynamic focusing can be combined to give 
a resultant beam which is both focused and angled.  
 The transducer array can also be used to perform so-called ?linear scanning?. It 
consists in successively fired adjacent groups of elements to create a scanning effect.  
  48 
 
The "Virtual Probe" width and scan pitch can be controlled by selecting the number of 
elements fired in parallel and the number of elements indexed for successive shots. This 
technique can be combined with both beam steering and dynamic focusing to apply a 
"scanning motion" to angled and focused beams.  
 
Figure 4.7: Electronic phasing used to create a focused sound field 
 
The advantages are: 
? Faster inspection of complete volume of thick pieces with dynamic focusing. 
? Electronic focusing can compensate for focusing aberrations due to cylindrical 
interfaces 
18, 40
. 
An array transducer may be constructed from a wide variety of sources, including 
piezoelectric elements as well as EMAT (Electromagnetic-Acoustic Transducer) and 
laser sources. This kind of system is very expensive as each circuit is essentially a 
separate ultrasonic system controlled by the multiplexer. But the increased speed and 
versatility of inspection that the array transducers permit, however, may offer advantages 
that counter the added expense of the system 
14
. 
  49 
 
These phased array transducers are used in inspecting complex geometries such as 
rotor shafts for turbines and components for nuclear reactors. Figure 4.8 shows some of 
the commercially available phased array transducers. 
  
 
 
Figure 4.8: Commercially available phased array transducers 
 
The adaptability of these kinds of probes reduces the set-up time required for 
making varied inspections on these geometries, since from one probe placement, different 
parts of the component can be inspected by just changing the firing scheme of the probe 
elements. 
 
 
 
 
 
 
 
 
 
 
 
 
 
  50 
 
 
 
5. LUMBAR SPINE ANATOMY 
 
The spine works as the main support for the spinal cord and the nerves that carry 
information from the arms, legs, and rest of the body, and carries signals from the brain 
to the body. Without a functioning spinal cord, one could not move any part of the body, 
and the organs could not function. Our back is composed of 33 bones called vertebrae as 
shown in fig 5.1
 41
, 31 pairs of nerves, 40 muscles and numerous connecting tendons and 
ligaments running from the base of the skull to the tailbone or coccyx.  
 
 
 
Figure 5.1: Human Spine 
 
 
  51 
 
 
5.1 Spinal Column 
 
The spinal column is made up of 33 small bones called vertebrae that are stacked or 
jointed together to create the spinal column. 
The spinal column is separated into 5 specific functional areas: 
? Cervical / C 1-7  
? Thoracic / T 1 - 12  
? Lumbar / L 1 - 5  
? Sacral  
? Coccyx  
The cervical, thoracic and lumbar are the three main segments of the spinal column 
(Figure 5.1) 
41
. The cervical spine is the upper part of the spine, comprised of seven 
vertebrae (C1 to C7). The cervical bones are designed to allow flexion, extension, 
bending, and turning of the head. They are smaller than the other vertebrae, which allow 
a greater amount of movement. The thoracic spine is the center portion of the spine, 
comprised of twelve vertebrae (T1 to T12). The spinal canal in the thoracic region is 
relatively smaller than the cervical or lumbar areas. This puts the thoracic spinal cord at 
greater risk when there is a fracture. The motion that occurs in the thoracic spine is 
mostly rotational. The ribs prevent bending to the side. A small amount of movement 
occurs in bending forward and backward. The lower portion of the spine is called the 
lumbar spine. It usually comprises five vertebrae (L1 to L5); however, some people may 
have six lumbar vertebrae. Below the lumbar spine is the sacrum. The sacrum is actually 
a group of specialized vertebrae that connect the spine to the pelvis. At the terminal end 
  52 
 
of the spinal column is the coccyx, which is composed of four, fused undeveloped 
vertebrae. The normal spine has an "S"-like curve when looking at it from the side. This 
allows for an even distribution of weight. The "S" curve helps a healthy spine withstand 
all kinds of stress. 
In all of these vertebrae we have a fibrous, elastic cartilage in between the 
vertebrae called intervertebral discs. These act as "shock absorbers" which keep our spine 
flexible and cushion the hard vertebrae as we move, Fig 5.2a 
42
.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 5.2: Lumbar Spine a) General Structure, b) Ligaments around the vertebrae 
 
There is one disc between each vertebra; each disc has a strong outer ring of 
fibers called the annulus, and a soft, jelly-like center called the nucleus pulposus. Each 
vertebra is held to the others by groups of ligaments, figure 5.2b. There are also tendons 
that fasten muscles to the vertebrae. The spinal column also has real joints (just like the 
knee or elbow) called facet joints. The facet joints link the vertebrae together and give 
them the flexibility to move against each other. Each vertebra has an apperture in the 
a) 
b) 
  53 
 
center, so when they stack on top of each other they form a hollow tube that holds and 
protects the entire spinal cord and its nerve roots, figure 5.2a. The spine branches off into 
thirty-one pairs of nerve roots. These roots exit the spine on both sides through spaces 
(neural foramina) between each vertebra. 
5.2 Vertebrae 
 
 Vertebrae are the individual bones of the spine. These are the building blocks of 
the spinal column. The vertebrae protect and support the spinal cord. They also bear the 
majority of the weight put upon the spine. The body of each vertebra is the large, round 
portion of bone, figure 5.3. The exterior vertebral body consists of very hard bone 
(cortical bone), with more spongy bone (cancellous bone) and blood vessels inside. 
The body of each vertebra is attached to a bony ring. These rings create the hollow tube 
through which the spinal cord passes. The bony ring attached to each vertebral body 
consists of several parts. First, the laminae extend from the body to cover the spinal 
canal, or tubular opening in the center of the vertebrae. Second, the spinous process is 
the bony portion opposite the body of the vertebra. We feel this part when we run a hand 
down a person's back. Then there are two transverse processes which attach the back 
muscles to the vertebrae. Finally, the pedicle is a bony projection that connects to both 
sides of the lamina 
43
. 
 
  54 
 
 
Figure 5.3 ? Parts of a Lumbar Vertebrae 
 
5.3 Intervertebral Disc 
 
The intervertebral discs are flat, round "cushions" that act as shock absorbers 
between each vertebrae in the spine. There is one disc between each vertebra. Each disc 
has a strong outer ring of fibers called the annulus, and a soft, jelly-like center called the 
nucleus pulposus, figure 5.4. The annulus is the disc's outer layer and the strongest area 
of the disc. It also helps keep the disc's center intact. The annulus is actually a strong 
ligament that connects each vertebra together. The mushy nucleus of the disc serves as 
the main shock absorber. The nucleus is made up of tissue that is very moist because it 
has high water content. The water content helps the disc act as a shock absorber - 
somewhat like a waterbed mattress
 43
. 
Body 
Transverse  
Process 
Superior 
Articular  
Process 
Spinous 
Process 
Laminae 
Spinal 
Canal
Pedicle 
Inferior 
Articular  
Process 
  55 
 
 
Figure 5.4: Vertebrae with Intervertebral Disc 
 
5.4 Soft Tissue surrounding the lumbar spine 
 
 The osseous elements of the lumbar vertebral column are connected by a variety 
of structures that collectively are known as soft tissue. Ligaments of various types 
connect the vertebral bodies and the posterior elements of the vertebrae and span one or 
more segments, depending on the type of ligament and vertebrae level, figure 5.2b.  
The paraspinal muscles refer to the muscles next to the spine. They support the spine and 
are the motor for movement of the spine. The joints allow flexibility and the muscles 
allow mobility. There are many small muscles in the back - each controlling some part of 
the total movement between all the vertebrae and the rest of the skeleton. These muscles 
can be injured directly, such as when you have a pulled muscle or muscle strain of the 
back muscles. The muscles can also cause problems indirectly, such as when the muscles 
are in spasm after injury to other parts of the spine.  
 
 
 
Intervertebral Disc 
Vertebrae 
  56 
 
 
 
 
 
 
 
 
Figure 5.5 ? Cross Section  of Lumbar Spine Segment 
 
 Above the ligaments and muscles associated with the spine, there is outer material 
composed of connective tissue and layers of skin. The connective tissue, called the 
hypodermis attaches other tissues of the body to the skin and supports structures such as 
blood vessels and nerves. This layer is variable in thickness depending on the amount of 
fat stored in the tissue. Above this layer, there are two layers of skin present: the dermis 
and epidermis. The dermis is commonly two millimeters in thickness and is composed of 
fibrous tissue, capillaries, sweat glands, hair follicles and sensory nerve endings. The 
epidermis is commonly half of a millimeter in thickness, is composed of epithelial tissue 
and includes sebaceous glands, sweat glands and hair follicles 
18
. 
5.5 Facet Joint 
 
The facets are the "bony knobs" that meet between each vertebra to form the facet 
joints that join the vertebrae together. There are two facet joints between each pair of 
vertebrae, one on each side. They extend and overlap each other to form a joint between 
  57 
 
the neighboring vertebrae facet joints. Without the facet joints, we would not have 
flexibility in the spine, and we could only move in very straight and stiff motions.  
The facet joints are also known as synovial joints. A synovial joint, such as the 
knee or elbow, is a structure that allows movement between two bones. In a synovial 
joint, the ends of the bones are covered with a material called articular cartilage. This 
material is a slick spongy material that allows the bones to glide against one another 
without undue friction.  
 
Figure 5.6: Facet Joint 
 
Surrounding the facet joint is a watertight sack made of soft tissue and ligaments. 
This sack creates what is called the "joint capsule". The ligaments are soft tissue 
structures that hold the two sides of the facet joint together. The ligaments around the 
facet joint combine with the synovium to form the joint capsule that is filled with fluid 
(synovial fluid). This fluid lubricates the joint to decrease friction, just as oil lubricates 
the moving parts of a machine 
43
. 
 
 
 
 
 
  58 
 
 
 
6. INSTRUMENTATION AND METHODOLOGY 
 
6.1 Background Information 
 
In the field of chiropractic medicine, it is very important to measure the variations 
in the intervertebral distance when patients are treated by the Cox Flexion-Distraction 
technique. Previous research has attempted estimation of the distance between contiguous 
lumbar vertebrae by identifying specific points in each vertebra to be used as an 
anatomical reference from which the measurements could be made. The point had to be 
representative of a singularity that could be very clearly identified in successive trials by 
recognizing the echo pattern of the pulsed reflected from it. Based on this, the tip of the 
spinous process was selected as the anatomical reference, viewed from the posterior-
anterior orientation. Based on this, a B-scan program was developed and has been used to 
record the profile of reflections along a trajectory that completely covers two adjacent 
spinous processes. Distances between the vertebrae has been determined directly by the 
separation between the indications of the spinous process tips within the image. 
 
Here, we plan on measuring the distance between the lumbar vertebrae by imaging 
the transverse process instead of the spinous process. The reason behind this is that the 
distance between the spinous process becomes very small as we move up along the spine 
into the thoracic and cervical zones, and this makes the measurement of distance between 
the vertebrae from the spinous process difficult, but there are significant distances 
between the transverse process in these zones. We have used the same ultrasound 
  59 
 
equipment as used for previous research. The only change is the frequency of the 
transducer used. A B-scan program has been used to scan the transverse process and save 
the recorded image. Another program has been used to read the saved file and rebuild the 
image for the data analysis. 
6.2 Instrumentation 
The experiments were carried out in the Litee Laboratory and Veterinary School at 
Auburn University in Auburn, Alabama. 
A computer-controlled ultrasonic testing system, US-Ultratek PCIUT3100, in 
conjunction with a 3.5 MHz immersion ultrasonic transducer, Panametrics V384, was 
used to generate the ultrasonic waves and receive the reflections from the specimen. The 
ultrasonic system includes a pulser/receiver and a high speed analog to digital (A/D) 
converter board for a PCI bus. It generates a high voltage pulse from the PULSE OUT 
connector to excite the transducer for the generation of the acoustic signals. The same 
terminal is used to receive the electric pulse back from the transducer. The analog signal 
is converted into digital information at a maximum rate of 100MHz (100 millions 
samples per second), See Appendix B for more technical specifications.  The board was 
housed in external portable bus expansion hardware, Magma 2 Slot CardBus PCI 
Expansion System, consisting of a CardBus card, expansion bus cable, expansion mother 
board, and a chassis with power supplier (Figure 6.1).  
  60 
 
 
Figure 6.1: Ultrasonic Testing System 
 
The use of the PCI expansion system was meant to allow the use of a laptop, Dell 
Inspiron 6000, to operate the ultrasonic system. This configuration provided the 
portability required to move the whole system to different laboratories and the flexibility 
to unplug the component as desired, for instance, to use the computer in a different 
location for data analysis, etc.  
 The PCIUT3100 board included a software development kit for engineers to write 
programs to control the different parameters of the pulser/receiver and the A/D converter. 
Labview, version 6i, National Instrument, was used to write the programs for the 
different tests. The software development kit provided a dynamic link library with a 
single function call to control different tasks of the board and get the required data. By 
setting some features of the function call one can set board parameters such as: receiver 
  61 
 
gain, sampling frequency, filters, signal rectification, buffer length, pulse width, etc 
29
. 
See Appendix C for details regarding dynamic link library and control of board 
parameters.  
 The following is a description of the general functioning of the ultrasonic board. 
Also refer to figure 6.2.  
? The PCIUT3100 board generates a negative high voltage pulse from the PULSE OUT 
connector and then starts collecting data. 
? The pulse excites the ultrasonic transducer with user-defined pulse voltage, pulse 
width, and damping. 
? The receiver on the PCIUT3100 board inputs the ultrasonic signal through RECEIVE 
IN connector, or (as in our design) directly from the PULSE OUT connector. 
? The receiver clips out the high voltage of the signal and then makes the signal go 
through the amplifier, high pass filter, rectifier, DC offset adjustment, and low pass 
filter. 
? The signal then is directed to the A/D circuit where it is converted to digital data and 
stored in the memory of the board. 
? The data is captured from the memory of the board and saved in the computer RAM 
for further digital processing and displaying.  
  62 
 
 
Figure 6.2: Schematic representation of the functioning of the ultrasonic board 
 
6.3 Working of the ultrasonic system 
 
The main four parts of the ultrasonic system are the base, transducer, slider and the 
encoder. 
 
                          Figure 6.3: Scanning assembly configuration 
  63 
 
 The ultrasonic system was made out of a translucent acrylic material. As shown in 
Figure 6.3, the base or main body holds the slider which in turn carries the transducer. 
The transducer is inserted in the hole of the slider whose diameter is slightly longer than 
the transducer diameter. The transducer is set in a way that its tip does not touch the 
bottom level of the base, i.e. its tip is set couple of millimeters above the bottom level of 
the assembly. This arrangement protects the active element of the transducer, preventing 
any direct contact between the transducer and the specimen being tested. Once the 
transducer is adjusted at the desired height, it is fixed by a plastic tip set screw (Figure 
6.4).  
 
Figure 6.4: Slider holding the transducer at a fixed position 
 
This design provides a smooth gliding of the slider through the base slot, a desired 
feature at the time of performing the test. An incremental optical encoder is attached to 
one of the top corners of the main body (Figure 6.3).  This device translates mechanical 
motion (such as speed, direction, and shaft angle) into electrical signals. Appendix B 
provides detailed information of the functioning and technical specifications of the 
encoder.  
  64 
 
 
Figure 6.5: Displacement of the slider along the base slot 
 
 In this application, the encoder was used to precisely measure the displacement of 
the transducer along the base slot. A rubber wheel was attached near the tip of the 
encoder shaft. The wheel is in direct contact with the slider and provides the necessary 
traction to rotate the encoder shaft as the slider moves, figure 6.5. 
As the shaft rotates, the encoder converts real time shaft-angle into digital (square 
waves) output signals proportional to the number of windows on the optical code disc. 
An encoder counter was added to the pulser/receiver board to encode the signal received 
from the encoder output. Two call functions were then used to properly read and 
manipulate the counter data. The first of them sets the starting value of the encoder 
counter and the second one simply gets the values from the encoder counter.  The counter 
delivers integer numbers from -8388608 to 8388607. If the encoder wheel is moved in 
counter clockwise direction, the values will be positive and vice versa.  
 The rectangular groove in the base of the assembly was covered by a thin rubber-
type sheet creating a small air volume under the slider, (Figure 6.6). During tests, the 
volume is partially filled with water to provide the acoustic coupling necessary to 
  65 
 
propagate the ultrasonic energy from the transducer to the test specimen. The rubber 
sheet was glued to the base to avoid any water leaking.        
 
Figure 6.6: Rubber sheet glued at the bottom of the base 
 
6.4 Scanning Procedure 
 
 Test preparation begins with setting the transducer and encoder on the assembly 
and plugging up their outputs to the respective input connectors on the board. The 
maximum displacement of the transducer before it touches the encoder shaft (physical 
limit) is approximately 6.2 cm.    
 As noted above, a call function was set to read the data from the encoder counter. 
The starting value of the encoder counter was set at zero. This means that once the 
program has been run, the zero reference point is automatically set in the position where 
the slider begins rotating the encoder. Accordingly, if the slider is placed  somewhere 
between the origin of the slot and the encoder shaft (as in figure 6.5), the point exactly 
below the center of the transducer will be the zero reference point. In general, the slider 
will be positioned touching the back edge of the assembly to provide the maximum 
coverage along the assembly.  
  66 
 
 Once the program has been run, no measurements are made unless the encoder 
wheel rotates. The Labview program, also called virtual instruments, was programmed in 
such a way that the encoder counts trigger the testing protocol. This means that when the 
counter advances the first positive digit from zero to one, the whole measurement and 
storing protocol begins. 
As the transducer is moved, the counter keeps delivering values, and the scanning 
continues up to the point where the slider is stopped by the encoder shaft. A command in 
the program was set in such a way that as the slider is glided back up to a predetermined 
position (couple of millimeters back from the encoder shaft), the program automatically 
builds an intensity plot containing the information stored in a preset buffer. The 
denominated B-scan screen is shown in Figure 6.7. 
 
Figure 6.7: B-scan (intensity plot) representation and instrumentation settings 
 
  67 
 
Once the image has been generated, one can decide to save it using the ?SAVE? switch 
or to reset the screen to run another scanning. The new scanning is carried out just by 
gliding the slider back until it reaches the position chosen as starting point (back edge of 
the assembly). At that point the counter will read zero again, ?Counter Output?, and a 
command will reset the image instantaneously. If the slider is moved forward again, the 
encoder counter will start counting positive counts back. This in turn will start a new data 
acquisition process without clicking any button. This feature allows an agile scanning. 
The front panel of the ?virtual instrument? allows adjustment of important parameters, 
for instance, signal rectification, high and low pass filters, pulse width, sampling rate, 
gain, etc 
29
. In addition, it provides other capabilities such as multiple zoom, and two 
positioning cursors to compute the distance between any pair of points, cursor 
coordinates reader, etc.  More details about of the operation and features of the front 
panel may be found in any help-tutorial of Labview software. Appendix C provides more 
details regarding the B-scan program. 
6.5 Data Analysis 
 
 The ultimate goals of the data analysis procedure are to determine the distance 
between the transverse processes and evaluate the correlation between the images as well 
as the reliability of the measurements. In some parts we have the figures of the spinous 
processes to explain the data analysis and about the B-scan program. Each B-scan is 
created from a two-dimensional data array saved as a text string file for further analysis. 
The text files are loaded by a program written in labview, and an identical to the original 
B-scan display is re-built (Figure 6.8). As in the former program, the display has multiple 
imaging enhancement features such as different types of zooms, two cursors to compute 
  68 
 
the distance between any pair of points within the image, adjustment of different intensity 
thresholds to emphasize or disguise specific levels of amplitudes (brightness), distance-
reading indicator, etc.  
 
Figure 6.8: Front panel of the data analysis program 
 
 
Figure 6.9: Zoom in image of Figure 6.8 
 
Once an image has been loaded the intensity thresholds can be adjusted to improve the 
image definition of the spinous process indications regardless of the quality of the rest of 
Intensity 
thresholds 
  69 
 
the image. In fact, one could select a smaller area of the image containing just the spinous 
process indications (Figure 6.9), to obtain a better view of the shape and boundaries of 
each singularity. The measurement of the distance is achieved by positioning the cursors 
in the center of each spot. The ?DISTANCE? meter of the front panel shows the distance 
between the X-coordinate of each cursor, which represents the distance between the 
spinous process tips.      
6.6 Spatial Resolution, Encoder Resolution 
 
 The spatial resolution of the scanning refers to the number of excitations of the 
ultrasonic system, or, in other words, the number of samples taken for every millimeter 
that the transducer advances along the assembly. The greater the number of excitations, 
the better is the resolution of the system, which in turn implies a better accuracy in the 
scanning. This feature was restricted by the encoder resolution since the ultrasonic pulse 
generator was triggered as the encoder counter generated an output count. By 
experimental measurements it was established that 1972 counts were generated as the 
transducer displaced 56.8 mm. Dividing this distance by the number of counts one 
obtains that the separation at which every measurement is taken is mm028.0
1972
8.56
= . 
The proper performance of the ultrasonic system and computer diminished each time the 
transducer was moved fast along the assembly. Each time the encoder triggered the 
system, a complex and long procedure (excitation and reception of the ultrasonic pulse, 
analog to digital conversion of the information, data acquisition and processing, etc.) was 
carried on. The vast amount of data being acquired and processed by the computer in 
each excitation (due to the high sampling frequency) demanded a minimum time that can 
be exceeded if the encoder is rotated too fast. When this minimum time is surpassed, the 
  70 
 
computer is unable to consistently synchronize the data collection with the data storing, 
resulting in the creation of incoherent images.  To ensure the usefulness of the scanning it 
was necessary to apply a delay to the scanning excitation rate. This was achieved by 
setting the program to start the scanning (excitation of the pulse generator) every 
increment of 4 of the encoder counter. In other words, four counts were skipped at every 
excitation. This fact in turn decreased the spatial resolution to one fourth the original 
resolution which corresponds to 0.112 mm. This rate is still excellent considering the 
order of magnitude of the separation between the center of the S.P. tips (experimentally 
found to be between 25 to 40 mm, depending on the size of the subject) and the size of 
their tip sections (between 5 to 20 mm depending on the size of the subject) 
18
.  
6.7 Selection of the Transducer 
 
 The selection of the transducer obeyed geometrical and performance criteria. 
Sensibility and resolution of several probes acting on a human bone target (radius of a 
human arm) and on the artificial model were evaluated. The best results were achieved by 
immersion transducers since those are designed to match the acoustic impedance of water 
which is very close to that of soft tissue, 1.5?10
6
 [Kg/m
2
s]
 
 and 1.6?10
6
 [Kg/m
2
s]
 
respectively.  The 2.25MHz - 1/4" element size and 1.0MHz - 1/2" element size 
immersion transducers from Panametrics are selected for this purpose.  
 
  71 
 
6.8 Test Sessions 
 
 Several testing sessions were conducted in LITEE Laboratory and the Veterinary 
School at Auburn University. The tests were carried out on artificial spine model. Each of 
the test sessions followed specific goals and procedures as it will be detailed next. 
6.8.1 Tests on the Artificial Spine Model Using Customized Ultrasound System 
 
 The lumbar plastic spine segment is immersed in an unflavored gelatin solution, 
and left till it solidifies as shown in figure 6.10. A thin layer of gelatin covers the spinous 
process tips.  
 
Figure 6.10: Artificial lumbar spine in the gelatin solution 
 
The gelatin simulated the soft tissue surrounding the bone. Several samples of different 
concentration were tested in order to find the texture and flexibility that better matches 
soft tissue characteristics. The final concentration was of about 100 ml of water for every 
7.06 g of gelatin powder.  
The average wave propagation speed in the gelatin solution was, c= 1517 m/s, 
which correlates very well with the wave propagation speed of tissues such as fat (1450 
m/s), muscle (1590m/s), and water (1480 m/s). This result added to the similitude in 
  72 
 
texture and flexibility and made gelatin a good approximation of the vertebrae-
surrounding tissue without offsetting the effect of the heterogeneous nature of real tissue. 
 Tests of the artificial model were meant to measure the distance between the 
lumbar vertebrae by imaging the transverse process instead of the spinous process.  
Imaging the transverse process is important because the distance between the vertebrae is 
very small as we move up along the spine, and it really becomes difficult to measure the 
distance between the vertebrae by imaging the spinous process. The spinous process 
image in the cervical and thoracic zones will not be sufficiently clear to measure the 
distance between the vertebrae, but the distance between the transverse process will be 
significant which makes distance measurement easy.  
 Two immersion transducers of frequencies 2.25 MHz and 1 MHz were obtained 
from the leading manufacturer Olympus for this experimentation. The diameter of these 
two transducers was ? inch. We had a new slider manufactured (as shown in Figure 
6.11), especially for holding these two transducers, as the early slider had a small hole 
which was not sufficient to hold the new transducers.  Translucent acrylic was used as the 
material for the slider. 
 
Figure 6.11: New slider with large diameter hole 
  73 
 
For conducting experiments on the plastic lumbar spine, the necessary gel was 
prepared and the plastic spine was immersed in it and allowed to solidify. With this done, 
the assembly was carefully placed on the top of the different segments of the spine 
covering at least two contiguous transverse process tips in each scanning (as shown in 
Figure 6.12). A thin layer of water was spilled on the surface of the gelatin to allow the 
propagation of sound from the rubber film to the specimen. Provision was taken to 
remove any air bubble between the rubber film and the specimen surface as well as to 
fully cover the transducer tip with water during the whole test. An air bubble would 
obstruct the propagation of the wave to the specimen which would result in unexposed 
zones invalidating the test or leading to data interpretation error.  
 
Figure 6.12: Scanning procedure of artificial sample 
 
            It was necessary to search for the best position above the transverse processes so 
that good reflections were received from their tips. The translucent nature of the gelatin 
eases this task making it possible to complete the data collection in a few minutes 
depending on the experience of the operator. 
  74 
 
 The LabVIEW B-scan program was used for this data acquisition. In general, the 
occurrence of a well defined and isolated peak would characterize the presence of a bone 
in the trajectory of the beam. The 2.25 MHz and 1 MHz immersion transducers were 
used for this scanning, but we did not get any reflections from the transverse process. 
Some reasons for not getting the image of the transverse process may be: 
1) Due to the depth of the transverse process from the surface of the gelatin solution. 
Physical measurement showed that the transverse processes are 35 mm to 40 mm 
deep from the surface. 
2) Due to the contour of the transverse process. The shape of the transverse process 
is very curvilinear which makes the ultrasonic wave to deflect from their path; 
thus waves may not reflect back. 
3) Due to the immersion transducers which did not have enough energy to transmit 
the ultrasonic waves deep enough. 
 These shortfalls of the customized ultrasonic system required us to go to other 
ultrasonic devices to scan the transverse process. Thus we conducted the same 
experiments in the Veterinary School at Auburn University using the highly sophisticated 
ultrasound system, Philips HDI 5000, at that facility.  
 
 
  75 
 
6.8.2 Tests on the Artificial Spine Model in VET School ? Auburn University 
 
Tests were next conducted on the artificial spine model using the Philips HDI 
5000, ultrasonic system. These tests were conducted to check for the feasibility of 
measuring the distance between the lumbar vertebrae by imaging the transverse 
processes. 
6.8.2.1 Specifications of the Ultrasonic System ? Philips HDI 5000 
 
The physical dimensions of the ultrasonic system shown in Figure 6.13 are: 
? Weight ? 380 lbs 
? Height ? 62 in (including the monitor) 
? Width ? 28.35 in 
? Depth 39.35 in 
 
Figure 6.13: Philips HDI 5000 Ultrasound System 
 
 
  76 
 
This machine offers the different imaging modes: 
? Gray-Scale 2D 
? M-Mode 
? Doppler 
? Color 2D 
? Color M-Mode 
? Tissue Doppler Imaging (TDI) 
The 2 Dimensional expresses a measurement with two dimensions on a flat plane. 
It is a cross-sectional representation of anatomical structures. 2D images also display 
motion. The position, texture, shape and dynamics of the anatomy displayed in the 2D 
image are presented in real-time. The 2D image is also used to orient the scanhead for M-
Mode, Doppler, Color, and Power imaging.  The 2D image allows us to locate the area of 
interest for magnification during the M-mode zoom. During the Doppler imaging, the 2D 
image provides a reference for sample volume, depth and size, and Doppler angle 
correction. The 2D image also provides the reference for the color display during the 
color and power imaging.  
 Using this 2D display, the scrolling Doppler display provides blood flow 
direction, speed, timing information and quality. An understanding of hemodynamics (i.e. 
study of the forces involved in the circulation of blood) and timing of normal and 
abnormal blood flow allows one to diagnose pathology using the Doppler display. M-
Mode or Motion Mode is used with the 2D display. A line within the 2D image 
represents the M-line. Over time the movement of the anatomy along the M-line creates a 
scrolling display. M-mode is primarily used for cardiology imaging.  
  77 
 
 Color flow imaging uses Doppler principles to generate a color image. Color is 
related to velocity and direction in the color flow imaging. This information is then used 
to overlay a color image onto the 2D gray scale display. The color flow image provides 
information about blood flow direction, speed, quality and timing. Color flow imaging 
helps you locate blood flow disturbances. Tissue Doppler Imaging (TDI) is a color 
Doppler imaging technique used primarily in cardiology to display ventricular wall 
motion.  
It can be used for diagnosis of abdominal, adult Cardiology, advanced breast 
imaging, cardiology contrast specific imaging (CSI), gynecological and Ffertility, 
musculoskeletal, neurology, obstetrical, pediatric/fetal cardiology, peripheral vascular, 
prostate and transcranial doppler 
20
. 
6.8.2.2 Experiments Using Philips HDI 5000 Ultrasound System 
 
These experiments were also conducted in the Veterinary School at Auburn 
University. The purpose of conducting these experiments was to find a suitable system 
for future work. The artificial lumbar spine model was set up in the gelatin solution 
before the experimentation (shown in Figure 6.14). 
 
Figure 6.14: Artificial Lumbar Spine in Gelatin Solution 
  78 
 
The Philips HDI 5000 system was equipped with three kinds of transducers. We 
have used the Linear Array Transducer having a varying frequency from 5 to 12 MHz. It 
has 128 elements and 38mm effective aperture length. This can be used to image 
vascular, small parts, breast, and musculoskeletal areas.  
 We started with imaging the transverse process of the L1 vertebrae using the 
linear array transducer. For proper coupling between the transducer and the gelatin 
surface, ultrasound gel was used. This coupling allowed for proper transmission and 
receiving of ultrasonic waves to and from the transducer.  We were able to get the image 
of the L1 transverse process which was very difficult to image using our customized 
ultrasound system.  
Using this highly sophisticated ultrasound system, Philips HDI 5000 we then measured: 
1. The width of the transverse process on both sides of the vertebral body 
2. Distance between the two contiguous transverse process 
3. Depth of the transverse process from the surface of the gelatin surface 
4. Width of the spinous process 
5. Distance between the spinous process vertically along the body of the 
spinous process. 
We began with measuring the width of the transverse process on the right side of 
the vertebral body. Once the linear array transducer was placed exactly on top of the 
transverse process, we obtained the real time 2D image on the screen. The transducer was 
moved until we get a better quality image of the transverse process. While doing this we 
could change the frequency of the transducer in real time. Once we saw the good quality 
image we were able to freeze the image on the screen and then measure what ever was 
  79 
 
needed using the cursors available to measure the distance. The distance measured could 
be seen on the lower left side of the picture. We also labeled the parts as shown in Figure 
6.15. Once we made all the necessary measurements and labeling we saved the image on 
the machine. These saved images can then be transferred to the computer and later used 
for analysis purpose. The Figure 6.15 shows the width of the transverse process of the L1 
vertebra. The width of the L1 transverse process was found to be 6.8 mm (or 0.68 cm).  
 
Figure 6.15: Width of the L1 Transverse process on the right of the vertebral body 
We did similar experiments on both sides of the vertebral body to measure the 
width of the transverse process. Figure 6.16 shows the width of the L1 transverse process. 
  80 
 
 
Figure 6.16: Width of the L1 transverse process on the left of the vertebral body 
 
Afterwards, the scans were performed covering all the transverse processes of the lumbar 
vertebra and making necessary measurements and labeling to identify them. 
 Our next activity was to measure the distance between the transverse processes. A 
procedure similar to the imaging the width of the transverse process was followed to get 
the image of the two transverse process in one image and thereby measure the distance 
between them (Figure 6.17). The figure below shows the distance between the L1 and L2 
transverse process on the right of the vertebral body. The distance was found to be 3.29 
cm from the top tip of the first transverse process to the top tip second transverse process 
and 3.26 cm when measured at the same level.  
  81 
 
 
 
Figure 6.17: Distance between the L1 & L2 transverse process  
 
Similarly the scans were performed to measure the distance between the other 
lumbar vertebra transverse process. 
Our next step was to measure the depth of each transverse process from the 
surface of the gelatin. Scans were performed to measure this, and Figure 6.18 shows the 
depth of the L4 and L5 transverse process from the top surface of the gelatin. 
  82 
 
 
Figure 6.18: Depth of L4 and L5 transverse process from the gelatin surface 
 
We then planned on measuring the length of each spinous process as shown in 
Figure 6.19, and comparing the value with the value obtained by our customized 
ultrasound system. Following the same procedure, we then measured the length of all the 
five spinous lumbar vertebrae using the linear array transducer. Figure 6.19 shows the 
length of the L4 spinous process, and it was found to be 0.82 cm (or 8.2 mm).  
  83 
 
 
Figure 6.19: Length of the L4 Spinous process 
 
The same spinous process has been imaged using our customized ultrasound 
system and the length was found to be 0.84 cm (or 8.41 mm). Figure 6.20 shows the 
length of the L4 spinous process obtained using our ultrasound system. 
  84 
 
 
Figure 6.20: Length of the L4 spinous process 
 
Finally scans were performed measuring the distance between the contiguous 
lumbar vertebrae vertically along the spinous process element as shown in Figure 6.21. 
Four to five measurements were made vertically along the spinous process. The figure 
below shows the four measurements made between the L3 and L4 lumbar vertebra. 
  85 
 
 
Figure 6.21: Vertical Measurements between the L3 and L4 lumbar vertebra 
 
Another important features of this HDI 5000 system is the dual image capability. 
The length of the transducer was not enough to image three lumbar vertebrae at once, so, 
we used the dual imaging control to get the three vertebrae in a single image as shown in 
figure 6.22. The dual image control displays two 2D images side by side on the screen. 
Initially, after the first scan was made we could freeze the image and scan again for the 
second image, and then we could overlap the second image on the first image as shown in 
Figure 6.22. 
  86 
 
 
Figure 6.22: Dual Image of L1, L2 and L3 vertebrae 
 
There is a disadvantage in using this dual image capability. We may not always 
be able to exactly attach the second image onto the first image where it has been cut. 
There will definitely some error in doing this. The only way to image three spinous 
processes is to use a linear array transducer having a long effective aperture length of 
around 50mm. 
As our customized ultrasound system had certain limitations, we had to look for 
other sophisticated ultrasound systems which could serve our purpose. Using this 
ultrasound equipment, HDI 5000, we were able to measure what we had planned, and it 
had all features what we needed. We also compared some of the values obtained from 
  87 
 
HDI 5000 system with our customized ultrasound system and evaluated our system?s 
accuracy. 
6.8.3 Simulating the Traction in the Artificial Lumbar Spine 
 
Flexion -Distraction is an excellent technique for the treatment of middle and 
lower back pain. It is a gentle and extremely effective technique that helps to decompress 
the spine and remove pressure on the vertebral disc. In addition, it restores range of 
motion to the spine and realigns the vertebrae. Theoretically, the tractioning or distraction 
of the disc combined with isolation and gentle pumping of the involved area allows the 
central area of the disc, the nucleus pulposus, to assume its central position in the disc. In 
simple words, traction is like a pulling or stretching force to remove the pressure from the 
discs and increase the distance between them.  
 We have simulated the traction condition in the artificial lumbar spine using the 1 
mm rings in between the vertebral body. First, we calculated the distance between the L1, 
L2 and L3 lumbar vertebrae without any 1 mm rings (as shown in Figure 6.23) in 
between them, and for the second set of scanning we inserted 1 mm rings in between the 
vertebral body and took the readings using our customized ultrasound system. Similarly 
we increased 1 mm more for the next set of experiments and so on until we had put 5 mm 
rings in between the lumbar vertebrae (as shown in Figure 6.24). This kind of setup 
simulates exactly what happens during the traction of the lumbar vertebrae. 
  88 
 
 
 
 
Figure 6.23: L1, L2 and L3 Vertebrae with no 1mm rings 
 
 
 
 
 
Figure 6.24: L1, L2 and L3 vertebrae with 5 mm rings in between 
  89 
 
 
 
7. RESULTS AND DISCUSSION 
 
7.1 Tests on the Artificial Spine Model  
 
The real time images obtained from the Philips HDI 5000 were very clear for 
analysis providing reliable information relating to the spinous and transverse processes. It 
also enabled us to make all necessary measurements and labeling on the image (as shown 
in Figure 7.1). This Figure shows the image of the L4 vertebra and transverse process of 
L5 vertebra. 
 
 
 
Figure 7.1: Image of L4 Vertebra and transverse process of L5 Vertebra from Philips 
HDI 5000 Ultrasound System 
 
In the above Figure, whenever we make any measurement, the value appears on 
the lower left hand corner of the image. When we make 2 or more measurements, each 
measurement has a different symbol to identify the measurement; this symbol can be seen 
to the left side of the measurement value (as shown in Figure 7.2). The units of the 
measurement are shown to the right side of the value as shown in Figure 7.2.  
  90 
 
 
Figure 7.2: Depth measurement of L4 and L5 transverse processes 
 
Experiments were conducted to measure the depth of the transverse process from 
the surface of the gelatin solution. Table 7.1 shows the depth measurements of the 
transverse process. 
 
Transverse Process Left (mm)  Right (mm) 
L1 29.9  24.1  
L2 34.9 20.8 
L3 34.2 27.4 
L4 44.8  31  
L5 34  26.9 
 
Table 7.1: Depth of the Transverse Process 
 
 
 
  91 
 
The next activity was to measure the width of each transverse process on both 
sides of the vertebral body. Table 7.2 shows the width of each transverse process in 
millimeters. 
Transverse Process Left (mm) Right (mm) 
L1 9.7   6.8  
L2 11.6 8.6 
L3 10.3 7.7 
L4 8.7  11.3  
L5 16.5  15.7  
 
Table 7.2: Width of the Transverse Process 
 
There was significant difference between the widths of the transverse process on 
the left and right side of the vertebral body. This explains the complicated shape of the 
transverse process and difficulty in imaging them. Moreover the shape of the transverse 
process is very curvilinear which makes the ultrasonic waves to deflect and makes it 
difficult to image using a single element immersion transducer. 
We also measured the distance between the transverse process on both sides of 
the vertebral body. Table 7.3 shows the distance between the transverse process. 
 
Transverse Process Section Left (mm) Right (mm) 
L1-L2 28.9  32.6  
L2-L3 34.4  29.2  
L3-L4 31.3  32.9 
L4-L5 28.1 29.5  
 
Table 7.3: Distance between the Transverse Process 
 
The shape of the lumbar vertebrae is very complicated as evidenced by the difference in 
measurements of the transverse process on both sides of the vertebral body. 
 
 
  92 
 
The length of the spinous process was also imaged and the Table 7.4 shows the 
values of it. 
Spinous Process Length (mm) 
L1 10.9 
L2 10.7  
L3 9.9 
L4 8.2 
L5 8.0 
 
Table 7.4: Length of the Spinous Process from Philips HDI 5000 
 
The same spinous processes length was measured using our customized 
ultrasound system. Figure 7.3 shows the length of the spinous process of L4 vertebra. 
 
Figure 7.3: Image of the spinous process of L4 vertebra using our ultrasound system 
 
 
  93 
 
Table 7.5 below shows the values obtained from our customized ultrasound system. 
 L1 L2 L3 L4 L5 
Trial 1 11.29 ? 0.11 10.60 ? 0.11 10.14 ? 0.11 8.41 ? 0.11 7.60 ? 0.11 
Trial 2 11.40 ? 0.11 10.71 ? 0.11 10.14 ? 0.11 8.64 ? 0.11 7.83 ? 0.11 
Mean (mm) 11.34 ? 0.11 10.65 ? 0.11 10.14 ? 0.11 8.52 ? 0.11 7.72 ? 0.11 
 
Table 7.5: Length of spinous process from our ultrasound system 
 
This spinous process length obtained from the two ultrasound systems was 
compared with the values obtained by vernier caliper. Table 7.6 shows the comparison of 
the spinous process length from the two ultrasound systems and the vernier calipers. 
Spinous Process Phillips HDI 5000 CV 
(mm) 
OUR SYSTEM 
(mm) 
Vernier Caliper 
(mm) 
L1 10.9   11.34 ? 0.06   11 ? 0.1 
L2 10.7  10.65 ? 0.06 10.4 ? 0.1 
L3 9.9  10.14 ? 0 9.8 ? 0.3 
L4 8.2 8.52 ? 0.12  8.5 ? 0.2 
L5 8.0  7.72 ? 0.12 8.2 ? 0 
 
Table 7.6: Comparison of Spinous Process Length 
 
 
The three kinds of measurement were compared and a graph plotted using those values 
(shown in Figure 7.4).  
 
 
 
 
 
 
 
 
 
 
 
 
  94 
 
Comparision of Two Ultrasound Systems and Vernier Calipers
0
2
4
6
8
10
12
12345
Lumbar Vertebrae
Le
ngt
h of
 S
p
i
nous
 
P
r
oc
e
s
s
 
(m
m
)
Philips System
Our System
Vernier Calipers
 
 
Figure 7.4: Comparison Graphing two ultrasound systems and vernier calipers  
 
The values obtained from the vernier calipers were considered as a standard and the 
difference in values from the customized ultrasound system and Philips ultrasound 
system has been calculated and shown in table 7.7 and table 7.8. 
Spinous Process Vernier Caliper 
(mm) 
Phillips HDI 5000 
CV (mm) 
Difference in Values 
(mm) 
L1 11 ? 0.1 10.9 0.1 
L2 10.4 ? 0.1 10.7 0.3 
L3 9.8 ? 0.3 9.9 0.1 
L4 8.5 ? 0.2 8.2 0.3 
L5 8.2 ? 0 8.0 0.2 
 
Table 7.7: Difference in spinous process length obtained from vernier calipers and philips 
system 
 
 
 
 
 
  95 
 
Spinous Process Vernier Caliper 
(mm) 
OUR SYSTEM 
(mm) 
Difference in 
Values (mm) 
L1 11 ? 0.1 11.34 ? 0.06 0.34 
L2 10.4 ? 0.1 10.65 ? 0.06 0.25 
L3 9.8 ? 0.3 10.14 ? 0 0.34 
L4 8.5 ? 0.2 8.52 ? 0.12 0.02 
L5 8.2 ? 0 7.72 ? 0.12 0.48 
 
Table 7.7: Difference in spinous process length obtained from vernier calipers and the 
customized ultrasonic system 
 
  The experiments conducted on the Philips HDI 5000 ultrasound system confirmed 
a lot of information and helped us to a better analysis of the lumbar vertebrae. The same 
ultrasound machine can be used to image the whole human spine with no difficulty. 
7.2 Tests on Artificial Spine Model ? Simulating the traction in the model. 
The traction conditioned has been simulated in the artificial lumbar vertebra by 
placing the 1mm rings in between the vertebral body.  
The most important sources of error linked to the testing system and procedure of 
scanning were imprecision in the data collection and data interpretation. Data were 
collected at points that were assumed to be right above the spinous process tips. The 
center of the tips was displayed by well defined shades and their mid points were used to 
compute the distance between the bone tips. To have consistent measurements the same 
reference points needed to be picked in all measurements, which obligate one to follow 
the same trajectory over the tips during every scan.  This requirement was hard to comply 
with since there was no way to assure the probe was exactly in the same position above 
the bones. 
For the first set of experiments there were no 1mm rings placed in between the 
lumbar vertebral body; this simulates the human vertebra before the traction treatment. 
  96 
 
The Table 7.9 shows the values distance measured between the L1, L2 and L3 vertebra. 
We have calculated the Mean ( x
~
), Standard Deviation (SD) and Coefficient of Variation 
(CV) using the formulas: 
                                                     
n
x
x
n
i
i?
=
=
1~
                               7.1 
                                              
n
xx
SD
n
i
i?
=
?
=
1
2
)
~
(
        7.2 
                                             100.
~
x
SD
CV =                                7.3 
Where x
i
 represents the elements of the sample of size n, i = 1, 2?..n.  
Trials L1-L2 Segment (mm) L2-L3 Segment (mm) 
1 27.30  29.84  
2 27.30  29.84  
3 27.30  29.84  
4 27.42  29.84  
Mean 27.33  29.84  
 
Table 7.9: Distance between the Lumbar Vertebra with no 1mm rings 
  97 
 
Second set of experiments was conducted by inserting the 1mm rings in between 
the vertebral body. This kind of setup simulates the little traction applied to the lumbar 
vertebra. Four measurements of the distance between L1, L2 and L3 spinous processes 
were recorded, and the mean, standard deviation and coefficient of variation has been 
calculated. Figure 7.5 shows the distance between the L2 and L3 spinous process. In the 
Figure you can notice the 2 clear reflections from the two spinous processes and the 
distance between them.  
 
Figure 7.5: Distance between the L2 and L3 spinous process 
 
 
 
 
 
  98 
 
Table 7.10 shows the distance measured between the vertebras when 1mm rings are 
placed in between. 
Trials L1-L2 Segment L2-L3 Segment 
1 28.34  30.87  
2 28.11  30.87  
3 28.11  30.87  
4 28.34  30.87  
Mean 28.23  30.87  
 
Table 7.10: Distance between the lumbar vertebra with 1mm rings 
 
For the next set of experiments we placed 2 mm rings in the vertebral body. Table 
7.11 shows the distance measured between the L1, L2 and L3 lumbar vertebras when 2 
mm rings are placed in between. 
Trials L1-L2 Segment L2-L3 Segment 
1 29.26  31.80  
2 29.49  31.80  
3 29.26  31.80  
4 29.26  31.80  
Mean 29.32  31.80  
 
Table 7.11: Distance between the lumbar vertebrae with 2 mm rings 
 
Similarly we placed 3 mm, 4mm and 5mm rings in between the lumbar vertebral body 
and measurements were made. All these measurements were conducted to simulate the 
traction applied to the human lumbar vertebrae. In the traction mechanism also, we 
gradually stretch the vertebrae there by increasing the distance between the lumbar 
vertebrae and decreasing the pressure in between them. Tables 7.12, 7.13 and 7.14 show 
the distance measured between the L1, L2 and L3 vertebrae when 3mm, 4mm and 5mm 
rings are placed in between the lumbar vertebral body respectively. 
 
 
  99 
 
Trials L1-L2 Segment L2-L3 Segment 
1 30.30  32.83  
2 30.30  32.83  
3 30.30  32.83  
4 30.30  32.83  
Mean 30.30  32.83  
 
Table 7.12: Distance between the lumbar vertebrae with 3 mm rings 
 
 
Trials L1-L2 Segment L2-L3 Segment 
1 31.33  33.98  
2 31.33  33.87  
3 31.33  33.75  
4 31.33  33.75  
Mean 31.33  33.84  
 
Table 7.13: Distance between the lumbar vertebrae with 4 mm rings 
 
Trials L1-L2 Segment L2-L3 Segment 
1 32.37  34.68  
2 32.26  34.68  
3 32.26  34.79  
4 32.37  34.79  
Mean 32.31  34.74  
SD 0.06 0.06 
CV % 0.19 0.17 
 
Table 7.14: Distance between the lumbar vertebrae with 5 mm rings 
 
Once all the experiments were done by simulating the traction condition in the 
artificial lumbar spine, all that remained was to calculate the differences between the 
measurements for analysis and for calculating how accurately our customized ultrasound 
system had imaged the spinous process in each set of experiments. Table 7.15 shows the 
difference between the spinous processes distances when there are no 1mm rings to the 
distance when there are 1 mm rings in between the vertebral body. The calculated 
  100 
 
difference is very close to 1mm, which shows that the customized ultrasound system can 
accurately image the spinous process. 
 
 L1-L2 (mm) L2-L3 (mm) 
0 mm 27.33 29.84 
1 mm 28.23 30.87 
Expected Difference 1 1 
Obtained Value 0.9 1.03 
Error (mm) 0.1 0.03 
 
Table 7.15: Difference in the spinous processes distance when 1 mm rings are used 
 
Similarly the differences in the spinous processes distance were calculated when 1 
mm rings and 2 mm rings are placed. The values are shown in table 7.16. Even these 
values were very close to 1mm difference. 
 
 L1-L2 (mm) L2-L3 (mm) 
1 mm 28.23 30.87 
2 mm 29.32 31.80 
Expected Difference (mm) 1 1 
Obtained Value (mm) 1.09 0.93 
Error (mm) 0.09 0.07 
 
Table 7.16: Difference in the spinous processes distance when 2 mm and 1mm rings are            
used 
 
Similarly, differences in spinous processes were calculated when 2 mm, 3 mm, 4 mm and 
5 mm rings are placed in between the vertebral body. Table 7.17, 7.18 and 7.19 show the 
differences respectively. 
 
 
 
 
  101 
 
 L1-L2 (mm) L2-L3 (mm) 
2 mm 29.32 31.80 
3 mm 30.30 32.83 
Expected Difference (mm) 1 1 
Obtained Value (mm) 0.98 1.03 
Error (mm) 0.02 0.03 
 
Table 7.17: Difference in the spinous processes distance when 2 mm and 3 mm rings are  
                    used 
 
 
 L1-L2 (mm) L2-L3 (mm) 
3 mm  30.30 32.83 
4 mm 31.33 33.84 
Expected Difference (mm) 1 1 
Obtained Value (mm) 1.03 1.01 
Error (mm) 0.03 0.01 
 
Table 7.18: Difference in the spinous processes distance when 3 mm and 4 mm rings are 
                   used 
 
 L1-L2 (mm) L2-L3 (mm) 
4 mm 31.33 33.84 
5 mm 32.31 34.74 
Expected Difference (mm) 1 1 
Obtained Value  (mm) 0.98 0.90 
Error (mm) 0.02 0.10 
 
Table 7.19: Difference in the spinous processes distance when 4 mm and 5 mm rings are 
    used 
 
Finally, calculations were made by keeping the normal distance, with no 1 mm rings in 
between the spinous processes, as a reference or base line for calculating the difference 
for 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm rings as shown in Tables 7.20, 7.21, 7.22, 7.23 
and 7.24. Table 7.20 shows the differences calculated between the L1 - L2 and L2 ? L3 
when 1 mm rings are placed. The calculated differences were 0.9 and 1.03 mm, which are 
very close to the increased 1 mm distance. 
 
  102 
 
 L1-L2 (mm) L2-L3 (mm) 
0 mm 27.33 29.84 
1 mm 28.23 30.87 
Expected Difference (mm) 1 1 
Difference (mm) 0.9 1.03 
Error (mm) 0.1 0.03 
 
Table 7.20: Difference in normal spinous processes distance and when 1 mm rings are 
                    used 
 
 
The table below shows the normal distance between the L1, L2 and L3 spinous process 
and when 2 mm rings are place in between them. The differences calculated were 1.99 
and 1.96 mm, which are very close to the increased 2 mm distance. 
 
 L1-L2 (mm) L2-L3 (mm) 
0 mm 27.33 29.84 
2 mm 29.32 31.80 
Expected Difference (mm) 2 2 
Obtained Value (mm) 1.99 1.96 
Error (mm) 0.01 0.04 
 
Table 7.21: Difference in normal spinous processes distance and when 2 mm rings are 
used 
 
The difference calculated when 3 mm rings are used is 2.97 and 2.99 mm, which is very 
close to the increased 3 mm distance. 
 L1-L2 (mm) L2-L3 (mm) 
0 mm 27.33 29.84 
3 mm 30.30 32.83 
Expected Difference (mm) 3 3 
Obtained Value (mm) 2.97 2.99 
Error (mm) 0.03 0.01 
 
Table 7.22: Difference in normal spinous processes distance and when 3 mm rings are 
used 
 
 
 
  103 
 
Similarly the tables below show the differences calculated when 4 mm and 5 mm rings 
are used. 
 L1-L2 (mm) L2-L3 (mm) 
0 mm 27.33 29.84 
4 mm 31.33 33.84 
Expected Difference (mm) 4 4 
Obtained Value (mm) 4 4 
Error (mm) 0 0 
 
Table 7.23: Difference in normal spinous processes distance when 4 mm rings are used 
 
 L1-L2 (mm) L2-L3 (mm) 
0 mm 27.33 29.84 
5 mm 32.31 34.74 
Expected Difference (mm) 5 5 
Obtained Value (mm) 4.98 4.9 
Error (mm) 0.02 0.1 
 
Table 7.24: Difference in normal spinous processes distance when 5 mm rings are used 
 
All the values calculated were very close to the increased distance between the 
spinous processes. This proved that our customized ultrasound system can be used for 
measuring the distance between the spinous processes very effectively and accurately. 
  104 
 
 
 
8. CONCLUSIONS AND POTENTIAL FOR FUTURE DEVELOPMENT 
 
The reliable, agile and inexpensive ultrasound based testing system developed for 
this project was tested and used to measure the distance between the lumbar vertebrae in 
a human spine by imaging the spinous process under simulated traction conditions in an 
artificial spine model by inserting a series of rings between the vertebral components. 
The results obtained were both effective and accurate; for example, the standard 
deviation (SD) was 0.05 mm and the coefficient of variation (CV) was 0.18% for the 
distance between L1 and L2 when no rings were inserted, and the SD was 0 mm and CV 
was 0% for distance between the L2 and L3 vertebrae. Similarly, when 5 mm rings were 
inserted, an SD of 0.06 mm and a CV of 0.06% were obtained for the L1 and L2 segment, 
with an SD of 0.19 mm and a CV of 0.17% for the L2 and L3 segment.  
Moreover, the difference in the individual values was consistently in the range of 
?0.05 mm. An extensive literature review revealed no previous reported use of ultrasound 
to measure the intervertebral distance between adjacent lumbar vertebrae using the 
spinous process tips as the anatomical reference in flexion distraction chiropractic 
manipulation or under traction conditions alone.  
In continued testing experiments were conducted to measure the intervertebral 
distance between adjacent lumbar vertebrae by imaging the transverse process as an 
anatomical reference. For this experiment 2.25 MHz and 1 MHz immersion transducers 
were used to image the transverse process in an artificial spine model and a slider was 
constructed specifically to support these large diameter transducers. However, although 
  105 
 
multiple attempts were made, it was not possible to image the transverse process of the 
lumbar vertebrae, which represents a severe limitation of the new ultrasound system. The 
main reason for this inability to image the transverse process is thought to be the shape of 
the transverse process itself, which is very curvilinear. This causes the ultrasonic wave to 
be deflected in different directions and thus makes it impossible to collect the reflected 
ultrasonic waves using conventional immersion transducers. The literature search failed 
to reveal any previous reports of the use of ultrasound to measure the intervertebral 
distance of the adjacent lumbar vertebrae between transverse process tips as the 
anatomical reference in either flexion-distraction chiropractic manipulation or in the 
traction condition. However, the transverse process tips were used as the reference to 
measure the intervertebral distance in the lumbar zone during diurnal changes by 
Ledsome and Lessoway 
31
. 
Another potentially serious limitation of this system is the magnitude of the error 
inherent in the testing system and the scanning procedure. Data were collected at points 
that were assumed to be immediately above the spinous process tips. The center of the 
tips was displayed by well defined shades and their mid points were used to compute the 
distance between the bone tips. However, in order to obtain reproducible measurements, 
the same reference points must be selected consistently in every measurement, which 
makes it imperative to follow exactly the same trajectory above the tips for every scan.  
This requirement was difficuly to comply with under the conditions of this study since 
there was no way to ensure that the probe was in exactly the same position above the 
bones for each run. This led to significant imprecision in both the data collection and data 
interpretation steps. 
  106 
 
This inability to scan the transverse processes in the lumbar zone due to 
limitations in the scanning procedure, data collection and data interpretation made it 
necessary to seek a more sophisticated ultrasound system. The Auburn University School 
of Veterinary Medicine kindly made available their Philips HDI 5000 ultrasound system 
and this was used to gather a large number of additional measurements of the width of 
each transverse process and the distances between the adjacent transverse processes of 
the lumbar vertebrae. The length of the spinous process was also measured and compared 
with the values obtained using the ultrasound system constructed for this study. These 
two sets of values were also compared with vernier caliper measurements and the values 
obtained from all three data sources were found to be in good agreement.  
This comparison, as well as the experiments conducted to simulate traction 
conditions in the artificial spine, verified that the new system can be used to measure the 
distance between the adjacent lumbar vertebrae by imaging the spinous process. It is not, 
however, suitable for measurements of the transverse process. 
This research revealed that there is a great deal of potential for this new approach 
and it seems likely that many different kinds of experiments would benefit from the 
application of the customized ultrasound system developed for this study.  
Although the customized ultrasound system was not used on human subjects who 
were being treated by the flexion distraction technique for this study, future research 
should examine its use on human subjects to measure the intervertebral distance before 
and after the flexion distraction technique. An additional set of experiments should be 
conducted on the artificial spine model to simulate the traction condition, with 
  107 
 
experiments repeated on consecutive days to confirm the repeatability and reliability of 
the system.  
For further work, a highly sophisticated ultrasound system is needed. Using such 
a system will make it possible to image both the transverse processes and spinous 
processes in the lumbar zone and accurately measure the intervertebral distance. Other 
measurements of the artificial spine model can also be made, including: 
1) Measuring the width of the transverse process by taking 10 measurements along 
the contour of the transverse process and comparing the results with those 
obtained using vernier calipers. 
2) Measuring the vertical distance gap between the adjacent lumbar vertebrae and 
again comparing the results with those obtained using vernier calipers. 
3) Measuring the intervertebral distance by imaging the spinous and transverse 
processes. 
All these experiments should be performed at least twice to enable proper 
evaluation of the ultrasound technique in making these kinds of measurements. Once the 
principle has been established using the artificial spine model, the work can be extended 
to similar experiments on human subjects.  
This system can also be used to image the intervertebral disc height by applying 
conventional transabdominal ultrasound imaging techniques.
33
 The effectiveness of the 
flexion distraction intervention can be determined by imaging the surrounding tissue 
around the lumbar vertebrae, particularly the supraspinous and interspinous ligaments, to 
reveal exactly how their properties change as a result of flexion distraction chiropractic 
manipulation.
23
  
  108 
 
 
 
REFERENCES 
  
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Elsevier Science Publishing Co., Inc. 1985 
 
2. Z.H. Cho, Joie P. Jones, Manbir Singh. Foundations of Medical Imaging. John Wiley 
& Sons, Inc. 1993. 
 
3. D. Hans, T. Fuerst, F. Duboeul. Quantitative ultrasound bone measurement. 
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5. D.Wayne Rhodes, D.C. and Philip A. Bishop, Ed. D. A review of diagnostic 
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6. Jason C. Birnholz. Fetal lumbar spine: Measuring axial growth with ultrasound. 
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St.Luke?s Medical Center, Chicago. 1985. 
 
7. Zeynep Siklar, Efgan Sanli, Yildiz Dallar and Gulten Tanyer. Diurnal variation of 
height in children. Pediatrics International (2005) 47, 645-648. 
 
8. John R. Ledsome, Vickie Lessoway, Lark E. Susak, Faith A. Gagnon, Roy Gagnon, 
Peter C. Wing. Diurnal changes in lumbar intervertebral distance, measured using 
ultrasound. Spine Volume 21, Number 14, pp 1671-1675. 1996. 
 
9. Claudia Naish, Richard Mitchell, John Innes, Mike Halliwell, Donal McNally. 
Ultrasound imaging of the intervertebral disc. Spine Volume 22, number 2, pp 107-
113. 1996. 
 
10. R Gosling. Medical Imaging with ultrasound: Some basic physics. Phys. Educ. 24 
(1989).  
 
11. Kurutzne KM, Bene E, Lovas A, Molnar P, Monori E. Biomechanical experiments 
for measuring traction lengthening of the lumbar spine during weight bath therapy. 
Orv Hetil 2002 Mar 31 ; 143 (13) : 673- 84. 
 
12. Peter J. Shull. Nondestructive Evaluation. Theory, Techniques, and Applications. 
2002. 
  109 
 
 
13. Don E. Bray & Don McBride. Nondestructive Testing Techniques - 1992. 
 
14. Don E. Bray & Roderic K. Stanley. Nondestructive Evaluation ? A Tool in Design, 
Manufacturing, and Service. Revised Edition ? 1997 
 
15. Frederick W. Kremkau. Diagnostic Ultrasound - Principles, Instruments, and 
Exercises. Third Edition ? 1989. 
 
16. Jack Blitz and Geoff Simpson. Ultrasonic Methods of Non-destructive Testing, First 
Edition ? 1996. 
 
17. Josef Krautkramer. Ultrasonic Testing of Materials. Springer-Verlag, 1969. 
 
18. Determination of the distance between adjacent lumbar vertebrae by an ultrasonic 
based image system, Ariel M Medina. 
 
19. PCIUT 3100 ? SDKLV, Software Development Kit for LabVIEW, User?s Guide, 
UsUltratek, May 2002. 
 
20. Philips HDI 5000, ATL Ultrasound? Reference Manual- 1998. 
 
21. P H F Nicholsont, M J Haddaway: and M W J Daviet. The dependence of ultrasonic 
properties on orientation in human vertebral bone. Phys. Med. Biol. 39 (1994) 1013-
1024. Printed in the UK 
 
22. Marta Kurutz, Eva Bene, Antal Lovas, Erika Monori  and Peter Moln?r. Experimental 
Biomechanics of Human Lumbar Spine Segments.  
 
23. Seong-Hwan Moon, MD, Moon-Soo Park, MD, Kyung-Soo Suk, MD, Jin-Suk Suh, 
MD, Sang-Hoon Lee, MD, Nam-Hyun Kim, MD, and Hwan-Mo Lee, MD. 
Feasibility of Ultrasound Examination in Posterior Ligament Complex Injury of 
Thoracolumbar Spine Fracture. Spine 2002;27:2154?2158 
 
24. James W. Murakani, Bernadette L.Koch, Brian D.Coley, William E.Shiels, Gregory 
Bates and Mark Hogan. Diagnostic and interventional ultrasound of the pediatric 
spine. Pediatr Radiol (2001) 31: 775 ? 785, Springer-Verlag 2001. 
 
25. Dan Nemet, Tzipora Dolfin, Baruch Wolach and Alon Eliakim. Quantitative 
Ultrasound Measurements of Bone Speed of Sound in Premature Infants. Eur J 
Pediatr (2001) 160: 736 ? 740. 
 
26. Jason C. Birnholz, MD. . Fetal Lumbar Spine: Measuring Axial Growth with 
Ultrasound. Radiology 807, Volume 158, Number 3. 
 
  110 
 
27. Gretchen A. W. Gooding, MD, Mitchel S. Berger, MD, Gregory D. Linkowski, MD, 
William P. Dillon, MD, Philip R. Weinstein, MD, James E. Boggan, MD. Transducer 
Frequency Considerations in Intraoperative US of the spine. Radiology 273, Volume 
160, Number 1. 
 
28. Claudia Naish, Richard Mitchell Et Al. Ultrasound Imaging Of The Intervertebral 
Disc. Spine, Vol 28, N
o
 2, Pp 107-113, 2003.  
 
29. Weiss Gary. Spinal Ultrasound: Clinical Correlation Of Spinal Ultrasound And MRI. 
AJPM, Vol 6, N
o
 4, October 1996. 
 
30. Osmo Tervonem Et Al. Ultrasound Diagnosis Of Lumbar Disc Degeneration. Spine, 
Vol 16, N
o
 8, 1991. 
 
31. John Ledsome,Vickie Lessoway. Diurnal Changes In Lumbar Intervertebral Distance, 
Measured By Using Ultrasound. Spine, Vol 21, N
o
 14, Pp 1671-1675, 1996. 
 
32. PCIUT 3100 ? SDKLV, Software Development Kit for LabVIEW, User?s Guide, 
USUltratek, May 2002. 
 
33. Osmo Tervonen, MD, Seppo Lahde, MD, and Heikki Vanharanta, MD. Ultrasound 
Diagnosis of Lumbar Disc Degeneration. Comparison of computer 
tomography/discography. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  111 
 
 
 
APPENDICES 
 
 
 
 
 
 
 
 
 
  112 
 
 
 
APPENDIX A 
 
LITERATURE REVIEW ON IMAGING OF LUMBAR VERTEBRAE AND THE 
INTERVERTEBRAL DISTANCE USING THE ULTRASOUND  
 
The following is a literature review of the most significant investigations done in the area 
of diagnostic and quantitative ultrasound as well as in the biomechanics of lumbar spine. 
The review consists in a summary of the articles describing their objective, methodology 
used and the results. 
 
A.1 Review of Research Papers 
 
1. The dependence of ultrasonic properties on orientation in human vertebral bone 
  Speed of sound (SOS) and broad-band ultrasound attenuation (BUA) were measured in 
cubes of human trabecular bone from lumbar venebrae, in the three major anatomical 
axes. The three major anatomical axes are: 
 1) Cranio-caudal (cc) 
 2) Antero-posterior (AP) axes, 
 3) Lateral (LT)axes 
There were significant differences in the SOS and BUA when measured across the 
different axes. SOS was approximately 500 m s
-1
 greater than in either the lateral (LT) or 
antero-posterior (AP) axes, and BUA was approximately 23 dB MHZ
-1
 cm
-1
 greater. 
Small, but significant, differences existed between the AP and LT axes for both SOS and 
BUA. In the AP and LT directions, strong linear correlations existed between SOS and 
apparent density (correlation coefficient, r = 0.90), and between BUA and apparent 
density (r = 0.96). In the cc axis, correlations with density were poorer 
21
. 
 
2. Experimental Biomechanics of Human Lumbar Spine Segments 
The aim of research was to clear the biomechanical background of traction bath therapy 
curing low back pain problems, moreover, to obtain the mechanical characteristics of 
human lumbar segments for the FEM model of human spine in tension. The authors 
developed a special subaqual ultrasound method for measuring the deformations of the 
lumbar segments of human body suspended in water. Special software has been used for 
analyzing the ultrasound pictures. In vivo deformations of segments L3-L4, L4-L5 and 
L5-S1 have been measured. Experiments were conducted on 155 adult patients taking 
around 3000 ultrasound pictures of 400 segments.. Biomechanical parameters like sex, 
age, weight, height of the body and the viscoelastic behaviour of segments have been 
analyzed. Just after being suspended in water, 30-50% of patients shows instant elastic 
tensile deformation, by registering a mean value of 1, 0-1,1 mm elongation per segments. 
At the end of the 20 minutes long weightbath treatment, elongation of lumbar segments 
have been registered practically in 55-60% of patients without any extra weights, and in 
70-85% of patients with 20-20N extra lead loads applied on the ankles. The total mean 
viscoelastic elongation of human lumbar segments is about 1,2-1,7 mm in average of 
  113 
 
deformable segments. As for the biomechanical parameters, a significant difference has 
been demonstrated in reaction time of men and women. Women react more slowly, 
however, after 20 minutes the deformations are equal to that of the men 
22
.  
 
3) Feasibility of Ultrasound Examination in Posterior Ligament Complex Injury of 
Thoracolumbar Spine Fracture 
 A study was done one 12 patients with thoracolumbar spinal fractures, to assess the 
feasibility of ultrasound examination for posterior ligament complex injury in 
thoracolumbar spinal fractures. In posterior ligament complex injury of thoracolumbar 
spine fracture, the reliability of magnetic resonance imaging (MRI) for diagnosis has 
been reported. Nevertheless the usefulness of ultrasound for diagnosis has not been 
studied, whereas diagnostic ultrasound has been applied in the musculoskeletal 
system.Two healthy volunteers without a history of spinal trauma were recruited for pilot 
examination of the ultrasound procedure to access normal findings of the posterior 
ligament complex. This study investigated 12 thoracolumbar spine fractures. Four were 
flexion distraction injury, six were stable or unstable burst fractures, and two were simple 
compression fractures. Ultrasound was performed over the injured area by an experienced 
musculoskeletal radiologist in addition to radiography and MRI. Five patients underwent 
operative procedures to stabilize the fractured spine. Imaging data and operative findings 
were correlated with ultrasound examination. In the patients who did not undergo 
surgery, agreement in diagnosis between MRI and ultrasound was moderate (5 of 7) and 
in the patients who underwent surgery, correlation between MRI, ultrasound, and 
operative findings was excellent, especially in diagnosing the status of the supraspinous 
and interspinous ligaments. Nevertheless, it is impossible to visualize deep seated 
structures (i.e., ligamentum flavum, deep muscles of the spine, and facet joint) with 
ultrasound. This study demonstrated the excellent diagnostic ability of ultrasound to 
detect the status of the supraspinous and interspinous ligaments, especially in patients 
who undergo surgery. Although ultrasound examination appears to be less sensitive than 
MRI in predicting ligament status, the cost effectiveness of ultrasound and its use as an 
alternative to MRI in special situations (i.e., patients with pacemaker, ferromagnetic 
implant, or severe claustrophobia) should be emphasized 
23
.  
 
4) Spinal Ultrasound: Clinical correlation of spinal ultrasound and MRI 
The objective of this study was to determine the clinical utility of spinal ultrasound by 
demonstrating its sensitivity to patient clinical history and neurological examination and 
to compare its findings to the findings of MRI. Ultrasound was found to have an 
increased sensitive when compare with MRI in detecting injuries and inflammation of the 
spinal structures, it was more highly consistent with patient?s history and clinical 
examination. The study confirms the usefulness of spinal ultrasound especially in soft 
tissue application. This raises the conclusion that less expensive ultrasound should be 
used as a screening test prior to a more expensive MRI for low back pain. There exist the 
needs of statistically validate studies 
29
.   
 
 
 
  114 
 
5) Diagnostic and interventional ultrasound of the pediatric spine 
Research was done to show that the ultrasound can be used as a diagnostic tool in the 
evaluation of the pediatric spine. MRI is the primary modality for spine imaging in 
children and adults, ultrasonography is an important and useful modality in the neonate 
and infant. The non-ossified posterior elements of the infant offer an excellent acoustic 
window for evaluation of the spine. With ultrasonography, exposure to ionizing radiation 
is avoided, no patient sedation is required and accurate diagnoses are generated. High 
resolution linear array transducers up to 15MHz are used for getting the excellent detail 
of the spine from a posterior approach. They were successful in imaging children  up to 1 
year of age, although the quality of ultrasound images often decreases markedly after 
approximately 6 months of age due to increased posterior element ossification. The 
ultrasound has been used for diagnosing various other kinds of diseases related to the 
human spine. At the end it was concluded that, despite MRI being the definitive modality 
for imaging the spine, ultrasound remains a powerful and viable tool for imaging the 
neonatal and pediatric spine and can successfully guide interventional procedures 
24
. 
 
6) Quantitative Ultrasound Measurements of Bone Speed of Sound in Premature Infants. 
Experiments were conducted to measure the bone speed of sound in premature infants by 
quantitative ultrasound. Experiments were conducted on a total of 44 neonates which 
included 29 premature infants and 15 full term infants. The left tibial speed of sound 
(SOS) was measured by quantitative ultrasound. Bone SOS was successfully measured in 
all infants. A significant correlation between tribial SOS and gestational age (r=0.78, 
P<0.0005), but a significant inverse correlation between tibial SOS and post-natal age (r 
= - 0.78, P<0.0005). But bone SOS was significantly higher in full term infants compared 
to premature infacts. In conclusion, the results indicate that the tibial speed of sound was 
reduced in premature infants compared to full term infants 
25
. 
 
7) Fetal Lumbar Spine: Measuring Axial Growth with Ultrasound 
Ultrasound (US) can be used to visualize vertebral segments, suggesting a quantitative 
means of studying vertebral column growth in utero and thus a means of detecting 
developmental abnormalities. US images of the lumbar spine were obtained in 128 
clinically normal fetuses between the gestational age of 11 through 41 weeks. A large-
aperture, dynamically focused US system capable of regional magnification was used. 
Lateral coronal, transverse, and sagittal views of the lumbar spine were obtained with a 
large-aperture, dynamically focused array system, operated at a 3.5- on 5.0-MHz center 
frequency (Acuson 128; Mountain View, Calif.). The focal zone was placed at the depth 
of the spine, and selective magnification was used so that the lumbar spine occupied half 
or more of the horizontal extent of the display matnix (which is allocated dynamically 
over 1,024 pixels horizontally and 486 TV lines vertically). Preprocessing amplification 
was logarithmic, with a 30- on 40-dB plateau and mildly sigmoidal gray-scale assignment 
for slight accentuation of upper- level reflectors. Images were made with integration of 
four to ten successive video frames. Average lumbar spacing was calculated from 
distance between centrums of at least four lumbar bodies. The average distance between 
lumbar centrums increased nearly linearly throughout the second and third trimesters 2 
  115 
 
0.98). Enhanced anatomic display implies new capabilities for recognizing 
developmental abnormalities antenatally 
26
. 
 
 
8) Ultrasound Imaging of the Intervertebral Disc  
The main concern of this article is to determine the reliability of ultrasound imaging in 
the detection of structural changes associated with disc pathology. An In Vitro ultrasound 
imaging of dog intervertebral disc was performed. The discs of several dogs were 
stripped of all surrounding tissue and scanned using ultrasound before being sectioned 
and photographed. The ultrasonic images were compared with the photographs, which 
were graded previously in order to allow an evaluation of the progressive stage of the 
disc degeneration. Ultrasonic imaging of several disc demonstrated echo patterns that 
matched, in both location and appearance, real structural defects identifiable on the 
sectioned disc. This initial study shows that ultrasound images can contain a high degree 
of structural information, relate well with the pathologic condition of the disc, and is able 
to locate specific pathologic defects 
28
. 
 
9) Ultrasound Diagnosis Of Lumbar Disc Degeneration  
The purpose for this study was to evaluate the accuracy of ultrasound for imaging internal 
disc changes, and to asses its value as a screening method for symptomatic disc prior to 
CT/discography. A total of 56 discs in 29 patients were examined by both methods. The 
sensitivity of ultrasound for recognizing a discographically painful and deteriorated disc 
was 0.95, and its specificity was 0.38. Correspondingly, the predictive value of a positive 
US finding was 1.53, and that of the negative finding was 0.13. The reproductively of the 
US depend on the experience of the examiner to a great extent more than in other 
radiologic examination, and the system of classification has to be simple in order to keep 
the interobserver error at a reasonable level. Nevertheless, US proved a reliable method 
for detecting structural changes in intervertebral disc. It provides a cost effective method 
for screening prior to discography; if a disc is normal in US, a clinical significant lesion 
is improbable, and CT discography can be omitted. If US shows locally or generally 
increased the echogenicity, an intradiscal lesion is probably, and CT/discography needs 
to be perform to evaluate the clinically significance of the finding 
30
. 
 
10) Diurnal Changes In Lumbar Intervertebral Distance, Measured By Ultrasound  
The study measure the distances between the tips of the transverse processes of adjacent 
lumbar vertebrae (L1-L4) in the same subjects after one day of normal activities and 
again the next morning. Its objective was to evaluate the feasibility of directly measure 
the lumbar intervertebral distance using ultrasonography and to determine the magnitude 
of the diurnal change. Measurements were made on six occasions in each of six patients 
after 6:00 PM at evening and the following morning before rising. The results show that 
the measurements were done in an individual with a coefficient of variation of 7.5%. The 
reproducibility of the measurements of the total distance was better than ? 4%. The 
intervertebral distances between L1 to L4 were significantly greater in the morning than 
in the evening. These results shown that the measurement of the change in the distances 
between the lumbar vertebrae is feasible to perform by using ultrasonography 
31
. 
  116 
 
 
11) Transducer Frequency Considerations in Intraoperative US of the spine 
Intraoperative spinal ultrasound has been used on 15 patients to determine the effect of 
transducer frequency.  Fourteen men an one women underwent intraoperative US studies 
of the spine immediately after a spinal laminectomy had been performed. All patients but 
one had spinal stenosis and/or disk disease that affected the cervical cord (n=5), the 
thoracic cord (n=1), or the lumbosacral area (n=8). Three different commercial real-time 
units were available. Both 5 MHz and 10 MHz transducers were used on one patient and 
the transducer with the option of 3.5, 5 or 7.5 MHz was used in ten, and a 10 MHz 
transducer was used on four other patients. A 10 MHz frequency transducer produced 
images superior to images produced with either 5 MHz or 7.5 MHz transducers, as 
determined by characterization of fine morphologic detail of the spine with magnification 
of the image. The 3.5 MHz transducer frequency was suboptimal for diagnostic detail. 
Intraoperatively, the 10 MHz transducer, which had superior spatial resolution, produced 
the most detailed images of spinal cord, the surrounding subarachnoid fluid, the radicular 
arteries, and the dural sheath 
27
. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  117 
 
 
 
 
 
APPENDIX B 
 
TECHNICAL SPECIFICATIONS OF THE ULTRASOUND SYSTEM 
 
 
B.1 PCIUT3100 - Ultrasonic Pulser/Receiver and 100 MHz A/D Board for PCI Bus 
 PCIUT3100 is a combination of a pulser/receiver and a high-speed analog to 
digital converter on a single PCI board as shown in figure B.1. The board generates an 
electrical pulse with user-defined pulse voltage and pulse width. The pulse is transmitted 
to an ultrasonic transducer, which converts the electrical excitation pulse into an 
ultrasonic pulse. The pulse is then propagated into couplant or the material to be tested. 
The transducer receives the echoes that are reflected from the interface and converts the 
ultrasonic pulse back into an electrical signal. The on-board receiver processes the signal 
with the user defined parameters, and the A/D converter converts analog signals into 
digital data at a rate of 100 million samples per second. In addition, the digital data is 
transferred to a computer?s RAM at about 10 MB per second. The resolution of the 
conversion is 9 bits, which can scale from 0 to 511. The memory depth can reach up to 
256 kilo samples 
51
. 
 
Figure B.1: PCIUT3100 board 
  
  118 
 
B.1.1 Technical Specifications of PCIUT Board  
 
Pulse Voltage  
-40V to -300V, 256 steps. Higher voltages are 
available upon request. 
Pulse Width  
50 ns to 484ns, 256 steps Optional 15 ns is available 
upon request. 
Damping  620?, 340?, 200?, 160?, 60?, 55?, 50?, or 47? 
Internal Trigger  
10 Hz to 5000 Hz in 10 Hz increments when internal 
trigger is selected. 
Receiver Gain  0 dB to 80 dB in 0.1dB increments. 
DC Offset  -2.5V to +2.5V in 5mV increments 
Low Pass Filter  
All, 48MHz, 28MHz, 18MHz, 8.8MHz, 7.5MHz, 
6.7MHz, or 5.9MHz 
High Pass Filter  4.8MHz, 1.8MHz, 0.8MHz, or 0.6MHz 
Waveform  Full rectify, + half rectify, - half rectify, or RF 
Sampling Rate  
100MHz, 50MHz, 25MHz, 12.5MHz, 6.25MHz, 
3.125MHz, 1.5725MHz, and external clock < 100MHz
Transducer Mode  Single (Pulse/Echo) or dual (through transmission) 
Resolution  8 bits (0 to 255) or 9 bits (0 to 511) 
Memory  16 kilo samples and 256 kilo samples 
Waveform Length  16 to 16382 in 4 sample steps 
Trigger Source  external, internal or software 
Connectors  
3 BNC connectors: Pulse out, receiver in, and external 
trigger in 
Post Trigger delay  2 to 32764 samples in 2 sample step 
Dimensions  
12.5"x4.25" not including BNC and PCI edge 
connectors 
Add-on Options  
- BNC external clock connector 
- BNC trigger sync output connector 
- Logarithmic amplifier 
- Distance amplitude correction 
- Up to 4 encoder counters and connectors 
- Two additional 14-bit A/D converters 
- 256K sample memory upgrade 
- Windows software development kits 
- Hardware security key module 
- Hardware key development kit 
- Multi-channel control option 
 
Table B.1: Technical specifications of PCIUT3100 board 
  119 
 
B.2 2 Slot CardBus PCI Expansion Systems 
MAGMA?s 2 slot CardBus PCI Expansion System is general purpose bus 
expansion system for the PCI local bus. MAGMA's 2 Slot Cardbus-to-PCI Expansion 
Systems provide two full-length 32-bit or 64-bit PCI slots in a separate enclosure 
(chassis) that connects to a PC notebook or Apple PowerBook (which do not have built-
in PCI slots) through a 32-bit CardBus slot, figure B.2.  With MAGMA's patented PCI 
Expansion Technology, everything installed in the enclosure actually acts as if it's inside 
the notebook. The PCI expansion system consists of CardBus card, an expansion bus 
cable, an expansion motherboard and a chasis with the power supply. 
 
 
 
 
Figure B.2: MAGMA's 2 Slot Cardbus-to-PCI Expansion Systems 
 
 
 
 
 
  120 
 
B.2.1 General Specifications:  
? Backplane: Two standard PCI slots and One non-standard PCI slot (32-bit/33MHz 
or 64-bit/33MHz)  
? Standard Expansion Cable Length: 1 meter (1.5 meter is optional)  
? PCI Local Bus Specification: Revision 2.2  
? PCI Bridge Architecture Specification: Revision 1.1  
? Interconnect Bandwidth: 132 MB/sec (Theoretical Max. of PCI 33/32) 
? MTBF: 25,000 hours  
? Operating Environment: 0? to 50? C Operating Temperature, -20? to 60? C Storage 
Temperature , 5% to 85% Relative Humidity, Non-condensing 
? Supported Operating Systems: Win XP, Win 2000, Win NT, Win ME, Win 98SE, 
Mac OS X (version 10.2.2+), Mac OS 9.x, and Red Hat Linux 9 
52
. 
B.3 Ultrasonic Transducer 
Panametrics Slim Line V384, 3.5 MHz immersion ultrasonic transducer, Figure B.3. This 
Video Scan series transducer is an untuned device that provides heavily damped broad 
band performance. This type of transducer are the best choice in applications where good 
axial and distance resolutions are necessary or in test that require improved signal-to-
noise ratio in attenuating or scattering materials. Figure B.4 shows the Video Scan 
performance of a 5MHz transducer. 
  121 
 
 
Figure B.3: Immersion Ultrasonic Transducer 
 
B.3.1 General Specifications: 
? Stainless steel case is only 0.38 in (10 mm) in diameter, ideal for limited access 
areas. 
? Standard connector style is Straight Microdot Connector (SM) 
? Available in 0.25 in (6 mm) and 0.125 in (3 mm) element diameters. 
 
Figure B.4: Signal waveform and frequency spectrum of a Video Scan 5 MHz transducer 
 
B.4 Assembly 
 The assembly is the component where encoder and transducer are held, figure 
B.5. It has two principal elements, the base body and the slider. Both are made out of 
reluctant high density acrylic. The base body was assembled bonding 5 machined parts 
together as shown in figure B.5. 
  122 
 
 
Figure B.5: Final Assembly 
 
 
 
 
 
 
 
 
 
 
  123 
 
 
 
APPENDIX C 
LABVIEW PROGRAMS AND DLL 
C.1 Dynamic Link Library 
 A dynamic link library PCIUTDLL.dll is provided with this software 
development kit to give a user an access to PCIUT3100 pulser/receiver and analog to 
digital converter board from a LabVIEW program. There is only one function call in the 
dynamic link library PCIUTParms() to send the parameters to the board and get 
acquired data as well as encoder information from the board. There are four parameters 
for the function call PCIUTParms(). 
int PCIUTParms(int mode, int board, DWORD wParam, int lParam); 
Parameter mode is a number starting from 1000 that defines the purpose of the function 
call. Different number specifies different control tasks. The values of this parameter are 
defined in the pciut.h file.  
Parameter board is the board number. A 0 specifies the first PCIUT3100 board in the 
computer. If an invalid board number is specified, the parameter will be downloaded to 
the active board. A function call with a valid board number will set the active board. 
Parameters wParam and lParam are the additional information past to the function. 
They have different meanings depending on the parameter mode.  
The modes of the Dll function used for the programming of the B-scan program 
are described next. For a complete description of all modes refer to reference 19. 
 
1 
4 
3 2 
5 
  124 
 
ISDATAREADY (mode = 1000), Get data status 
Get the status of the data acquisition process. 
wParam: not used 
lParam: not used. 
Return: 0 if no data in the memory yet. Otherwise there are data in the memory. 
SOFTWARETRIGGER (mode = 1001), Generate a software trigger 
Generate a software trigger. After this function call the board will generate a pulse from 
the PULSE OUT connector, and the analog to digital converter will start converting 
analog signal to digital data with the user-specified parameters. The digital data will be 
saved in the -board memory. 
To generate a software trigger, the trigger source needs to be set to software trigger. See 
the section. 
mode=1016 below for details. 
wParam: not used 
lParam: not used. 
Return: 1 if successful. 
SETSAMPLINGRATE (mode = 1002), Set Sampling Rate 
Set sampling rate. 
wParam: index which is from 0 to 7. Default is 0. 
0 - 100 MHz 
1 - 50 MHz 
2 - 25 MHz 
3 - 12.5 MHz 
  125 
 
4 - 6.25 MHz 
5 - 3.125 MHz 
6 - 1.5725 MHz 
7 - external clock 
lParam: Not used, Return: 1 if successful. 
SETLOWPASSFILTER (mode = 1004), Set Low Pass Filter 
Set receiver low pass filter. 
wParam: index which is from 0 to 7. Default is 0 which means no filter. 
0 - No filter 
1 - 148 MHz 
2 - 28 MHz 
3 - 18 MHz 
4 - 8.8 MHz 
5 - 7.5 MHz 
6 - 6.7 MHz 
7 - 5.9 MHz 
lParam: Not used 
Return: 1 
SETHIGHPASSFILTER (mode = 1005), Set High Pass Filter 
Set receiver high pass filter. 
wParam: index which is from 0 to 3. Default is 3 which means 0.6 MHz. 
0 - 4.8 MHz 
1 - 1.8 MHz 
  126 
 
2 - 0.8 MHz 
3 - 0.6 MHz 
lParam: Not used 
Return: 1 
SETRECTIFIER (mode = 1006), Set Rectifier 
Set receiver signal type. 
wParam: index which is from 0 to 3. Default is 3 which means RF signal (no 
rectification). 
0 - Full wave rectify 
1 - positive half rectify 
2 - negative half rectify 
3 - RF signal (no rectification) 
lParam: Not used 
Return: 1 
SETDAMPING (mode = 1007), Set Damping Resistor 
Set the pulser damping resistor value on a single channel PCIUT3100 card. Use 
SETMCHANDAMPING or SETCHANDAMPING to set the damping resistors on a 
multi-channel board DT16B (or DT8B.) 
wParam: index which is from 0 to 7. Default is 0 which is 620 ohms. 
0 ? 620 ohms 
1 ? 339 ohms 
2 ? 202 ohms 
3 ? 159 ohms 
  127 
 
4 ? 60 ohms 
5 ? 55 ohms 
6 ? 50 ohms 
7 ? 47 ohms 
lParam: Not used 
Return: 1 
SETTRANSDUCERMODE (mode = 1008), Set Transducer Method 
Set the transducer method, pulse/echo or through transmission on single channel 
PCIUT3100 card. Use SETCHANTRANSDUCERMODE or 
SETMCHANTRANSDUCERMODE to set the transducer mode on a multi-channel 
board DT16B (or DT8B.) 
wParam: index which is 0 or 1. Default is 0 which is pulse/echo. 
0 ? pulse/echo. In this case the board connects PULSE OUT and RECEIVE IN together. 
1 ? through transmission 
lParam: Not used 
Return: 1 
SETBUFFERLENGTH (mode = 1009), Set Buffer Length 
Set the buffer length that specifies how many data samples that the next acquisition will 
collect data. 
wParam: number of samples to take. It ranges from 16 to 16382 in step of 4 samples. 
Default 
value of the buffer length is 4000 samples. 
lParam: Not used 
  128 
 
Return: 1 
SETPULSEVOLTAGE (mode = 1011), Set Pulse Voltage 
Set pulse voltage. 
wParam: index which is from 0 (-300V or ?350V with ?350V option) to 255 (-40V). The 
default is 255 which is -40V. Section 3.35 describes how to get the information about the 
?350V pulse voltage. Pulse voltage can be set from -40 V to -300 V. The formula is pulse 
voltage (V) = -(4 + 4000 / (0.392157 x Index + 13.5)).  
Use the following formula to calculate the pulse voltage for ?350V option pulse voltage 
(V) = -(4 + 4000 / (0.392157 x Index + 11.56)) 
lParam: Not used 
Return: 1 
SETPULSEWIDTH (mode = 1012), Set Pulse Width 
Set pulse width. 
wParam: index which is from 0 to 255. Default is 0 which is the minimum pulse width. 
The minimum pulse width Wmin can be obtained by using function call mode=1025. 
Normally it is 50 ns or 28 ns with special order. Pulse width can be set from minimum 
pulse width to 480 ns. The formula is Pulse width (nanoseconds) = 18 + (760.8 x index) / 
(161.67 + Index). If the result is less than Wmin, Wmin should be used. 
lParam: Not used 
Return: 1 
SETGAIN (mode = 1013), Set Gain 
Set the receiver gain. This function sets the gain of both fixed gain amplifier and the 
DAC amplifier. If DAC is on, this function sets the fixed amplifier only. The DAC gain 
  129 
 
can be set by using function call mode=1015. When the gain is a negative number, the 
amplifier acts like an attenuator. At this point the attenuation is not linear to the 
calculated value. So the attenuation value is not reflecting the true attenuation. The 
number is just for reference. 
wParam: index which is from 0 to 1023. It specifies the total gain from -20 dB to 80 dB 
for both amplifiers, or -10 dB to 40 dB for the fixed gain amplifier along. Default is 511 
which is 30 dB of the global gain. Receiver gain can be set from -20 dB to 80 dB with 
about 0.1 dB resolution. The formula is Receiver gain (dB) = 0.0978 x (Index ? 204) 
lParam: Not used 
Return: 1 
SETDCOFFSET (mode = 1014), Set DC Offset 
Set the receiver DC offset. 
wParam: index which is from 0 to 1023. Default is 511 which is 0V. 
DC offset can be set from ?2.5V to 2.5V with 5mV resolution. The formula is DC offset 
= 0.005 x Index 
lParam: Not used 
Return: 1 
GETENCODERCOUNTER (mode = 1017), Get Encoder Counter 
Get the encoder counter from one of the counters. 
wParam: index of the counter. 
0 ? first encoder (X axis) 
1 ? second encoder (Y axis) 
2 ? third encoder (Z axis) 
  130 
 
3 ? forth encoder (W axis) 
lParam: Not used 
Return: counter value from -8388608 to 8388607. 
SETENCODERCOUNTER (mode = 1018), Set Encoder Counter 
Set the value of an encoder counter. 
wParam: index of the counter. 
0 ? first encoder (X axis) 
1 ? second encoder (Y axis) 
2 ? third encoder (Z axis) 
3 ? forth encoder (W axis) 
lParam: counter value from -8388608 to 8388607. 
Return: 1 
GETDATA (mode = 1019), Get Digitized Data from Memory 
Get the digitized data from the memory on the board after the data acquisition.  
wParam: pointer of the receiving buffer: (unsigned char *) 
lParam: number of bytes to move from the board memory to the buffer. It should be 
multiple of 4. 
Return: -2 if wParam is NULL or 1 if successful. 
RESETCOUNTER (mode = 1020), Reset A/D Board 
Use this function call to reset the analog to digital converter before acquiring data. 
wParam: not used 
lParam: not used 
Return: 1 
  131 
 
RESETMEMORY (mode = 1021), Reset Memory 
Use this function call to clean up any data in the memory. It should be called before 
acquiring data. 
wParam: not used 
lParam: not used 
Return: 1 
SETOFFSETADJUSTMENT (mode = 1022), Reset DC Offset Adjustment 
Use this function call to set DC offset adjustment which can make the signal smoother. 
wParam: 0 - change the adjustment value and download it to the board 1 ? do the task 
above and save the adjustment value in the Non-Volatile memory on the board. So it can 
be retrieved when the program starts running again. 
lParam: adjustment value fro ?127 to 127. 
Return: 1 
GETMODELNUMBER (mode = 1023), Get Board Model Number 
Get the model number of the board. Normally it is PCIUT3100. 
wParam: pointer of the receiving buffer: (char *). It should have enough room for at least 
20 characters. 
lParam: not used 
Return: -2 if wParam is NULL or 1 if successful. 
GETSERIALNUMBER (mode = 1024), Get Serial Number 
Get the serial number of the board. The serial number can be used to verify which board 
you are talking to. 
  132 
 
wParam: pointer of the receiving buffer: (char *). It should have enough room for at least 
20 characters. 
lParam: not used 
Return: -2 if wParam is NULL or 1 if successful. 
GETMEMORYSIZE (mode = 1025), Get Memory Size 
Get the size of the memory. The returned value could be 16384 or 262144. 
wParam: not used 
lParam: not used 
Return: size of the memory. 
C.2 Labview Programs 
The B-scan program developed in Labview is presented in the next pages. In order to 
understand the elements of the diagram and the sequence of the operations the readers 
need to be familiar with Labview programming. Structures such as the one next to the 
symbol ???in the next page, are called sequences and contain multiple substructures. The 
subsequences are depicted in subsequent pages.  
 
 
 
 
 
 
 
 
  133 
 
C.2.1 Labview Diagram of B-scan Program  
 
 
 
12
Expanded next pages 
  134 
 
Sequence   1 
 
 
 
 
  135 
 
Sequence  2 
 
 
 
  136 
 
 
 
APPENDIX D 
COMMERCIAL ULTRASOUND SYSTEMS 
 
D.1 Introduction 
 
There are many highly sophisticated and multipurpose ultrasound systems 
available in today?s market.  
Some of the major companies developing these systems are 
1) Siemens 
2) General Electric 
3) Philips 
4) Aloka 
5) Pyramid 
6) TeraRecon 
 
D.2 General Electric (GE) Ultrasound System 
 
GE Healthcare's broad range of products and services enable healthcare providers 
to better diagnose and treat many diseases and disorders with ease. 
GE Healthcare has 15 major products grouped into four families in its global Ultrasound 
business: 
1) Leadership Ultrasound ? High end ultrasound systems like LOGIQ9, LOGIQ7, 
Voluson 730 and LOGIQWorks. 
2) Value Ultrasound ? Mid-range and portable ultrasound systems like LOGIQ5, 
LOGIQ3, LOGIQBook. 
3) Echo Cardiology Systems ? Ultrasound products related to Cardiac application like 
Vivid 7, Vivid 4, Vivid 3 and Echopac. 
4) Primary Care Diagnostic Systems ? Products related to bone densitometry 42. 
 
After a little research it was found that the LOGIQ Book XP which can be used for 
musculoskeletal imaging matches our requirement.  
The LOGIQ Book XP as shown in figure D.1
45
, is a high performance multipurpose color 
hand-carried imaging system designed for abdominal, obstetrics, gynecology, vascular, 
musculoskeletal, small parts, pediatric and neonatal applications. 
  137 
 
 
 
Figure D.1: LOGIQ Book XP from GE 
 
D.2.1 Specifications 
Dimensions and Weight 
? ? Height: 78 mm(3.07 in)console only 99.5 mm (3.92 in)with handle 
? ? Width: 350 mm (13.78 in) 
? ? Depth: 280 mm(11 in) console only 430 mm (12.6 in) with handle 
? ? Weight: approx. 4.2 kg (9.2 lb.) 
Console Design 
? Laptop Style 
? Integrated HDD (20GB) 
? Wireless LAN Support 
? 1 probe p ort with micro-connector 
? Rear handle 
Scanning Methods 
? Electronic Convex 
? Electronic Linear with slant scanning 
Transducer Types 
? Convex Array 
? Microconvex Array 
? Linear Array 
 
  138 
 
Operating Modes 
? B-Mode 
? M-Mode 
? Color Flow Mode (CFM) 
? Power Doppler Imaging (PDI) 
? Pulse Wave Doppler(PWD) 
Standard Features 
? High Resolution 10.4 inch Color LCD 
? 435 Frames (15 sec) Standard CINE 
? Memory (64MB) 
? 20GB(over 4,000 images) Hard Drive 
? Loops storage-from?on the fly? scanning and from memory 
? Automatic Optimization 
45
 
 
D.2.2 Price: 
The total cost of the equipment is $39,040.00. This includes: 
1) LOGIQ BOOK XP Compact Digital Ultrasound Console 
2) 8L-RS Probe: This is a wide band liner probe 4 ? 10 MHz which supports small 
parts, vascular, musculoskeletal, pediatrics and breast imaging. It has a 39 mm 
aperture. 
3) 3S-RS Phased array transducer: Wide band multi-frequency transducer with 
bandwidth between 1.5 and 3.6 MHz. This can be used for imaging and screening, 
abdominal, trauma, and Transcranial imaging. 
 
More information can be found on the official website of GE, 
http://www.gehealthcare.com/usen/ultrasound/products/logiq.html 
 
D.3 Philips HD11 XE Ultrasound System 
 
The Philips HD 11 XE Ultrasound System is shown in Figure D.2. From its digital 
broadband beamformer with proven SonoCT imaging, to its powerful XRES image 
processing, every HD11 XE system is built for High Definition performance. This means 
enhanced edges and margins for more sharply defined structures, with reduced noise and 
speckle, for better visibility and contrast of even the smallest structures. Clinicians are 
demanding smaller, higher performing systems specifically designed to meet their 
clinical and operational challenges. The new Philips HD11 XE system provides a 
powerful architecture for superb High Definition performance; elegant design for 
ergonomics, mobility and ease-of-use; and a versatile suite of applications and options for 
highly-flexible configurations 
50
. 
 
  139 
 
 
 
 
Figure D.2: Philips HD 11 XE Ultrasound System 
 
D.3.1 Specifications: 
The HD11 XE system provides the foundation for an ergonomic environment that adapts 
to virtually any scanning condition for optimal user comfort and convenience. 
? Its independent adjustment of monitors and controls, specifically monitor and 
control panel height and articulation, meet Industry Standards1 for the prevention 
of WRMSD, facilitating neutral working postures and reducing repetitive stress 
injuries. 
? The HD11 XE features an ultra-bright, flickerless LCD flat panel display for 
reduced eye strain in rooms that are dark or bright. 
?  Users experience less fatigue ? department productivity and workflow are 
optimized1. 
? As the lightest and smallest system in its class, the HD11 XE system is the 
ultimate for portability?no more moving the most challenging patients to take 
advantage of advanced imaging capabilities on larger high performance machines. 
? Up to five available ports reduce bending to switch out transducers. 
? Advanced circuitry helps keep users and patients more comfortable by promoting 
a quiet and cool scanning environment. 
? The integrated footrest allows correct posture, reducing stress on the spine 
50
. 
  140 
 
D.3.2 Applications 
? Pediatric 
? Breast 
? Vascular 
? Transesophageal 
? Musculoskeletal 
? Orthopedics 
? Doppler 
? Cardiac 
 
D.3.3 Transducer 
? The HD11 XE system supports over 20 transducers, including many from the 
Explora line, for flexibility in meeting most any clinical need.  
? New superflex cable technology is extremely flexible and lightweight, 
dramatically easing wrist strain.  
? Explora transducers feature new low-loss lens design and next generation 
microelectronics to deliver maximum acoustic efficiency for greater penetration 
and resolution 
50
.  
L12-5 50 mm 
? Fine pitch, 256 elements, high resolution linear array 
? 12 to 5 MHz extended operating frequency range  
? 50mm effective aperture length  
? 10 degrees of trapezoidal imaging  
? Steerable pulsed wave, color Doppler, and Color Power Angio, Panoramic, 
SonoCT , XRES and harmonic imaging  
? High resolution superficial applications including vascular, small parts, breast, 
and musculoskeletal imaging  
? Supports stainless steel, reusable biopsy guides (up to 14 gauge)  
D.4.4 Price 
 
The Price of the Philips HD 11 XE ultrasound system is $75,000. 
  141 
 
D.4 Siemens Sonoline G20 ultrasound System 
 
The SONOLINE G20? ultrasound system, shown in figure D.3, quickly distances 
itself from the competition with next-generation all-digital system architecture that 
utilizes Siemens technology migration. Individual imaging parameters have been 
optimized for a wide variety of clinical applications and patient types 
48
. 
 
? All-digital signal processing technology creates excellent image quality. 
? State-of-the-art beamforming provides a wide acoustic aperture, improved image 
       resolution, uniformity and penetration for difficult-to-image patients. 
? All-digital G20 system architecture enables seamless integration of advanced 
capabilities including DICOM connectivity solutions, Tissue Harmonic Imaging 
(THI) and TGO? tissue grayscale optimization technology. 
? Ongoing performance enhancements, which require only simple, cost-effective 
software upgrades, protect your initial investment into the future. 
? Slim, lightweight design with small footprint and four swivel wheels makes the 
system ideally suited for use in tight workspaces and easily maneuverable from 
suite to suite and patient to patient. 
? Intuitive interface with the familiar Windows?-based operating system promotes 
efficient and ergonomic system control via on-screen menus and proprietary 
ReadySet? workflow shortcuts. 
? The operating system software supports all standard applications, exam specific 
imaging presets, measurements, pictograms, annotations, reports, worksheets and 
system diagnostics 
? QuickSet? user programmable system parameters and integrated cine review 
streamline exams and enhance workflow 
? TGO technology for instantaneous, one-button image optimization 
? Tissue Harmonic Imaging (THI) is available to enhance visualization, particularly 
in difficult-to-image patients 
? MultiHertz? multiple frequency imaging optimizes penetration and resolution to 
expand the clinical versatility of each transducer 
48
. 
 
 
  142 
 
 
Figure D.3: Sonoline G 20 Ultrasound, gray scale imaging 
D.4.1 Specifications: 
? Ultrasound imaging system supporting linear and convex transducers in the 
frequency range of 2.8 to 10.0 MHz. 
? Imaging modes of B, M, A and their combinations. Field size (depth) from 3 cm 
to 24 cm. Comprehensive measurement, calculation and report packages 
integrated. 
? Monitor 12 Inch (non-interlaced). 
? DIMAQ Integrated Ultrasound Workstation standard. 
? CD-RW for Patient Studies, Presets, Quicksets, reports, system software. 
 
 
D.4.2 Applications: 
? Small Parts 
? Breast 
? Vascular 
? Musculoskeletal 
? Orthopedics 
 
D.4.3 Transducers 
The 7.5L75S linear array transducer uses ultra-sensitive wideband 128-element 
technology for improved resolution and penetration. User-selectable MultiHertz multiple-
frequency imaging expands its clinical versatility. 
 
  143 
 
Features include: 
? 2D, M-Mode frequency range: 5-8 MHz 
? Doppler frequency range: 7 - 5 MHz 
? Active field of view: 67 mm 
? Optional stainless steel biopsy attachment 
48
 
 
D.4.4 Price: 
The total equipment cost around $24, 860 including 
1) SONOLINE G20 Ultrasound system with operating system 
2) 7.5L75S Linear Array Transducer 
 3) Mitsubishi B&W Thermal Printer 
 
More information can be found on: 
http://www.medical.siemens.com/siemens/en_AU/gg_us_FBAs/files/brochures/Sonoline/
G20Brochure.pdf#search=%22sonoline%20g20%20specifications%22 
 
 
D.5 Aloka 
The ProSound SSD-4000, shown in figure D.4 utilizes the most advanced acoustic 
technologies available today, and its multidisciplinary technology architecture enables it 
to offer great versatility and flexibility over a wide range of clinical applications. 
The system employs a Pure Harmonic Detection (PureHD) feature to create exceptionally 
clear images?artifact free and with a higher signal-to-noise ratio. This is especially 
useful when scanning traditionally difficult-to-scan patients (e.g., the aged or the obese). 
The PureHD technology enables distortion-free fundamental frequency transmission as 
well, which makes harmonic images much clearer. This maximizes the affect of both the 
Tissue and the Contrast harmonic echo by providing excellent contrast and spatial 
resolution 
47
. 
 
  144 
 
 
Figure D.4: Aloka SSD 4000 Utrasound System 
D.5.1 Specifications 
Scanning Method 
? Electronic Convex Sector 
? Electronic Linear 
? Electronic Phased Array Sector 
 
Image Display Modes  
? B: gray-scale imaging 
? M 
? Flow: Color Doppler and Power Flow imaging 
? Dual B 
? B and M 
? B and D 
? B(Flow) 
? Dual B(Flow) 
? M(Flow) 
? B(Flow) and M(Flow) 
? B(Flow) and D 
? Triplex mode: B, Flow, and PW Doppler simultaneous real-time display 
? Dual Dynamic Display (DDD): B and B(Flow) simultaneous real-time display 
 
  145 
 
System Dynamic Range 
? 172 dB 
Number of Processing Channels 
? 256 channels 
Frame Rate 
? Max. 500 frames/sec or more 
47
. 
 
D.5.2 Pricing 
The equipment costs $96,300.00, which includes 
1) SSD-4000 Surgery Color Console with Harmonic Imaging 
2) UST-579T-7.5 Side Fire T-Shaped Linear Probe (60 mm aperture) 
3) 1 UP-895MD Sony B/W Printer 
 
More information can be found on: 
http://www.aloka.com/products/view_system.asp?id=4 
 
 D.6 Pyramid 
 
The Pyramid 800 shown in figure D.5 is designed to enable improved ultrasonic 
diagnosis of the musculoskeletal system. It is a portable scanner utilizing a smaller 
monitor for improved contrast resolution of bones, muscles and tendons. High resolution 
7.5 Mhz linear array imaging, with electronic focussing, makes this the ideal 
musculoskeletal system. 
 
Figure D.5: Pyramid 800 Ultrasound System 
 
D.6.1 Specifications 
Probe Frequency: 3.5 to 7.5 MHz 
Scanning System: Electronic Convex and Linear Scanning 
Scanning Mode: B and M Mode 
Image processing: Pre-processing, Correlation-Processing, Interpolation 
Zooming: 
x
1, 
x
1.2, 
x
2 as well as depth shift 
Measuring & Calculation: Distance, Area, Circumference, Heart Rate 
  146 
 
Character Display: ID, Date, Time, Frequency, Gain, Zoom, Focus, Comments (with 
keyboard), etc. 
Power Requirements: 110V/220V, 140VA 
46
. 
 
D.6.2 Price: 
The total equipment costs only $9,500.00. This includes 
1) Main unit with digital scan converter 
2) 7.5 MHz Linear array probe 
3) Alpha-Numeric Keyboard 
4) Accessories : Dust-proof cover, Cables and Operation Manual 
5) Extra Accessories (not included in price): 
? 3.5MHz Linear Probe EZU-PL21  
? 5.0MHz Linear Probe EZU-PL22  
? 5.0MHz Transvaginal EUP-V12B  
? 5.0MHz Convex Probe EZU-PC2B  
? 5.0MHz Microconvex Probe EZU-PC4B  
? Sony Video Printer B/W UP-890  
? Trolley/Mobile Cart 
? 9 inch monitor
 46
. 
More information on this system can be found at: http://www.pyramidmed.com/pms-
ultrasoundsystems.html 
 
D.7 TeraRecon 
The UF-850XTD shown in figure D.6 from TeraRecon is a mid-range ultrasound system. 
This is ideally suited for musculoskeletal imaging applications. TeraRecon's XTrillion 
image processing chip technology provides the underlying foundation for achieving high 
frame rates and high definition imaging 
49
. 
 
Figure D.6: Cart Base Ultrasound system UF-850XTD from TeraRecon 
  147 
 
D.7.1 Clinical Benefits: 
? View soft tissue above and between underlying bones. 
? Assess complete and partial tears in tendons, ligaments, and muscles in a dynamic 
state by viewing pathology missed by static imagery or more expensive CT and 
MR. 
? Image superficial skeletal structures, muscle fibers, and nerves in the wrist. 
? Image discontinuity of cortical bone, bony spurs, and septic arthritis. 
? Visualize carotid artery stenosis, deep venous thrombosis, and peripheral arterial 
disease. 
? Assess abdominal pathology such as aortic aneurysm, liver pathology, gallstones, 
and kidney diseases. 
 
D.7.2 Specifications: 
? It has a footprint of 19?W x 32?D) featuring a Dual Receiving Digital Beam 
former with multi-frequency Transducer. 
? Features Digital storage on integrated high capacity hard disk or CDR/ RW or 
USB memory.  
? Features a 15-inch TFT Color LCD monitor, (DICOM 3.0 Connectivity, Print & 
Worklist capabilities are available options) 
 
D.7.3 Scanning Modes: 
Standard capabilities include B-Mode (2-D), M-Mode and Color M-Mode, Color Flow 
Mapping PW Power Doppler, Triplex mode and Tissue Harmonic Imaging and basic 
measurements and reporting packages. Fully Digital Platform Architecture and software 
oriented features allows for flexible expandability. 
 
D.7.4 Transducers: 
1) Linear Probe 38mm 6.0/7.5/9.0 MHz 
2) Linear Probe 30mm 8.0/10.0/14.0 MHz 
49
. 
 
D.7.5 Price: 
This total equipment costs $41,200.00. This includes 
 1) UF-850XTD Multi-function, All Digital Color Doppler Ultrasound System 
 2) Linear Probe 30mm 8.0/10.0/14.0 MHz - FUG-LG308-16A ? (for UF-      
      850XTD) 
 3) Linear Probe 38mm 6.0/7.5/9.0 MHz - FUT-LG386-9A ? (for UF-850XTD) 
 4) Mitsubishi P-93W A6 Monochrome Thermal Printer ? P-93W 
 
More information can be found on: http://www.terarecon.com/products/us_prod.html 
 
 
 
 
 
 
  148 
 
D.8 Comparison:  
The table D.1 shows the comparison of all the commercially available ultrasound system 
we have researched. 
 GE Siemens Pyramid Aloka TeraRecon Philips 
Price $39,040 $24, 860 $9,500 $96,300 $41,200 $70,000 
Type of Probes 
 
Linear  Linear Linear Linear Linear Linear, 
Aperture 
Length 
39 mm 75 mm 38 mm 60 mm 38mm 50 mm 
Application Abdominal, 
obstetrics, 
gynecology, 
vascular, 
musculoskeletal
, small parts, 
pediatric and 
neonatal  
Small Parts, 
Breast,Vascular
,Musculoskelet
al,Orthopedics 
 
Musculoskeleta
l 
Cardiac,Abdom
inal, obstetrics, 
gynecology, 
vascular, 
musculoskeletal
, urology and 
many more 
Musculoskeleta
l,  muscle 
fibers,nerves in 
the wrist, 
abdominal 
pathology, liver 
pathology, 
gallstones, and 
kidney diseases 
Pediatric, 
Breast, 
Vascular, 
Transesophagea
l, 
Musculoskeleta
l, 
Orthopedics, 
Doppler, 
Cardiac,Abdom
inal, Liver 
pathology,  
Muscles, 
obstetrics, and 
gynecology 
 
Cart base or 
Laptop Based 
Laptop Cart Cart Cart Cart Cart 
Availability in 
US 
Yes Yes Yes Yes Yes Yes 
Screen High 
Resolution 10.4 
inch Color 
LCD 
 
12 Inch 9 Inch 15 inch 15-inch 15 inch 
Display Color Gray Scale Gray Scale Color Color Color and 
grayscale 
Operating 
Modes 
B-Mode,  
M-Mode, 
Color 
Flow 
Mode 
(CFM), 
Power 
Doppler 
Imaging 
(PDI), 
Pulse 
Wave 
Doppler(P
WD). 
 
B, M, A and 
their 
combinations. 
B and M B: gray-scale 
imaging, M 
Flow: Color 
Doppler, 
PowerFlow 
imaging, 
Dual B, 
B and M, 
B and D, 
B(Flow), 
M(Flow), 
and D 
Triplex mode: 
B, Flow, and 
PW, Doppler 
simultaneous 
real-time 
display, 
Dual Dynamic 
Display. 
B-Mode (2-D), 
M-Mode and 
Color M-Mode, 
Color Flow 
Mapping PW 
Power Doppler, 
Triplex mode 
and Tissue 
Harmonic 
Imaging and 
basic 
measurements 
and reporting 
packages 
B-Mode (2D), 
M-Mode, 
Doppler, Power 
and Color 
Imaging, 2D 
Contrast 
Specific 
Imaging, 2D 
Pulse Inversion 
Harmonic 
Imaging, Tissue 
Doppler 
Imaging, Color 
Power Angio, 
Power Motion 
Imaging, ECG 
 
 
Table D.1: Comparison of Ultrasound Systems 
 
 
 
  149 
 
APPENDIX E 
 
These are the web references used in this research work: 
 
34. http://www.naturalcareli.com/flexion.html 
 
35. http://www.spineuniverse.com/displayarticle.php/article897.html 
 
36. http://www.logan.edu/pages/chiro_tech_cox.asp 
 
37. http://www.ndt-ed.org/ 
 
38. http://www.kettering.edu/~drussell/Demos/waves/wavemotion.html 
 
39. http://www.reedlink.com/ProductInfo~Productid~39528~ProductName~Ultrasoni
c-Transducers.html 
 
40. http://www.imasonic.com/Industry/PAprinciple.php 
 
41. http://www.spinalinjury.net/html/_anatomy_of_the_spinal_cord_co.html 
 
42. University of Maryland Spine Center, www.umm.edu/spinecenter/education 
 
43. www.spineuniversity.com 
 
44. http://www.gehealthcare.com/company/docs/ultrasound4.pdf 
 
45. http://www.gehealthcare.com/usen/ultrasound/products/lbook_index.html 
 
46. http://www.pyramidmed.com/pms-ultrasoundsystems.html 
 
47. http://www.aloka.com/products/view_system.asp?id=4 
 
48. http://www.medical.siemens.com/webapp/wcs/stores/servlet/ProductDisplay~q_c
atalogId~e_-1~a_catTree~e_100001,12805,12761~a_langId~e_ 
~a_level~e_0~a_productId~e_138562~a_storeId~e_10001.htm 
 
49. http://www.terarecon.com/products/us_prod.html 
 
50. http://www.medical.philips.com/main/products/ultrasound/general/hd11_xe/index
.htm 
 
51. www.usultratek.com , USUltratek 
 
52. www.magma.com , MAGMA.