A 4.7 Tesla 4-Channel Transmit and Receive MRI Quadrature Birdcage Coil Design and Fabrication for Monkey Head imaging

Abstract

Magnetic Resonance Imaging (MRI) is an image modality used for clinical diagnosis as well as general imaging research. Functional magnetic resonance imaging or functional MRI (fMRI) is an MRI procedure that measures brain activity by detecting associated changes in blood flow. The study described in this thesis is intended for MRI application. In order to acquire high-resolution MRI images, the signal detector, i.e., radio-frequency (RF) coils plays a pivotal role. In this study, we designed and fabricated a 4.7 Tesla high-pass 4-ch transmit and receive birdcage coil for fMRI monkey head imaging. During RF transmission, this birdcage coil generates a high-uniformity volume excitation which is desired by MRI experiments. During reception, the quadrature nature of the RF output enables an improvement of the signal to noise ratio (SNR) by over 40%. The coil was designed by applying numerical simulations at first. The hardware implementation was done by taking care of tuning, matching and mutual decoupling issues. Also, front end circuits including hybrid, T/R switch and pre amplifier are discussed. MRI images of a saline water phantom acquired with the fabricated coil in a 4.7 Tesla MRI scanner demonstrate a high-degree of excitation homogeneity and SNR, which correspond very well to the theory and numerical simulation results.