UCSF

Key engineering challenges associated with realizing the full potential of high field MRI are the design of phased array RF coils, the development of parallel imaging techniques for rapid imaging, and the determination of optimal acquisition parameters for various clinical applications. Parallel imaging techniques, which are enabled by phased array RF coils, take advantage of higher MRI field strengths by trading the higher SNR for imaging speed. I constructed a novel eight-channel non-overlapping phased array RF coil with capacitive decoupling for imaging of the brain and the hip, which was designed to minimize reconstruction-related SNR losses in parallel imaging. The design was aided by high frequency electromagnetic simulations that I programmed, and the coil was tested in various clinical applications, demonstrating quantitative performance improvements over a commercial eight-channel head coil. Higher field strengths improve the capability of intracranial time-of-flight MR angiography, an important fully non-invasive angiographic technique, due to the higher baseline SNR and the improved background suppression that is a result of longer T1 relaxation times. I optimized the acquisition protocol for 7T intracranial MRA, relying on a combination of simulations and experiments, and quantitatively verified the performance improvements over 3T. Using GRAPPA-based parallel imaging acquisition and reconstruction techniques that I developed, I designed a very high resolution (0.146mm3) protocol for 7T imaging of volunteers and patients with vascular disease. These techniques produced angiograms free from artifacts in all subjects, and correctly identified vascular pathology in patients.