Quantification Techniques for Arterial Blood Flow and the Left Atrium

Abstract

Cardiovascular dysfunction is a major cause of morbidity and mortally. As such, the characterization of the heart and surrounding vessels has a high clinical significance. The advent of cardiac magnetic resonance imaging (MRI) has provided an effective and efficient, noninvasive method of looking at the cardiovascular system. This thesis investigates the application of MRI in the quantification of two particular aspects of the cardiovascular system: arterial blood flow and the left atrium (LA). The use of pulse wave velocity (PWV) in flow quantification is explored. The majority of prevalent techniques use landmarks in the time-domain to calculate PWV. However, this presents problems with reliability due to the low temporal resolution of MRI flow data. A frequency-domain based approach through the use of the Fourier transform is investigated. This method is shown to be effective in minimizing errors found in the time-domain calculations. Dual-contour propagation is a post-processing technique used to produce contours. This is done through the propagation of manually drawn end-diastole (ED) and end-systole (ES) contours throughout the cardiac cycle. The method has been previously validated in regards to its applicability for ventricular data. The application of this technique with LA MRI images is considered and shown to be a valid propagation method. Finally, different approaches to volumetric quantification of the LA are explored. Issues are raised with the accepted serial short-axis and area-length calculation methods and a new virtual short-axis method is proposed. This method seeks to compensate for the inaccurate geometric assumptions made by the area length method whilst avoiding the time intensive use of the short-axis in quantification. This method is shown to be effective and efficient method for volumetric analysis.