Design of optimal radio frequency coils for improved signal-to-noise ratio in magnetic resonance angiography

The purpose of this dissertation was: (1) to develop Radio Frequency (RF) coil design and analysis tools, (2) to develop improved patient immobilization and positioning imaging procedures, and (3) to design and construct improved imaging coils for intracranial and carotid Magnetic Resonance Angiography (MRA). This was accomplished by performing volunteer imaging studies and computer simulations to determine which coil designs resulted in the highest Signal-to-Noise Ratio (SNR) for the application of interest. Coil design optimization tools were developed and applied to the design of individual coil and multicoil arrays. The importance of patient positioning was noted, and a patient positioning system for reducing these errors was developed. Individual coils were designed and demonstrated to provide significant improvements in image SNR.; It was determined that a reduced-volume endcap and phased-array coils, designed specifically for imaging the intracranial volume of the head, improved the image SNR and vascular detail considerably over that obtained using commercially available coils.; Carotid artery positional varyations as a function of head position were determined. A patient head/neck immobilization and positioning device was designed and constructed, and was shown to significantly reduced patient mobility during single scans and improve patient repositioning for longitudinal studies.; Computer simulations and volunteer measurements were used to assess the SNR improvement that might be obtained in carotid imaging using arrays that are not limited by a constraint on the number of RF receiver ports. Analytic near-field equations for the magnetic and electric fields of rectangular loop resonators were used to estimate the relative SNR along the length of simulated carotid arteries as a function of loop geometry and vessel depth.; This work also included the development of a quasistatic simulation model that accounts for coil-to-coil and coil-to-sample electromagnetic coupling interactions. Single and dual coil array designs were optimized using a Genetic Algorithm (GA) optimization scheme. Parametric evaluations were performed to determine the relative importance of coil design parameters for specific objects of interest. These studies provide the guidance and tools for future developments in MRA RF coil design and indicate the potential of future multicoil systems.