Radiofrequency Coil Design for Magnetic Resonance Imaging and Spectroscopy of the Human Breast and Models of Duchenne Muscular Dystrophy

Abstract

The known value of magnetic resonance imaging and spectroscopy (MRI/MRS) to detect and monitor disease with high sensitivity has driven researchers and clinicians to continually push boundaries beyond clinically-standard ^1H MRI. This has led to many advancements including high field MRI and MRS and non^1H MRI and MRS. MRI of the breast is commonly used as a supplemental tool to mammography throughout various stages of diseases. Specifically, benefits of high field MRI and the use of array coils have enabled studies such as dynamic contrast enhanced MRI (DCEMRI) and diffusion weighted imaging (DWI) with high spatial and/or temporal resolution. These studies provide additional information about morphology and kinetics of breast lesions to distinguish between malignant and benign tumors with improved diagnostic accuracy. MR imaging and spectroscopy have been used to study progressive muscular degenerative disorders, such as Duchenne muscular dystrophy (DMD). ^1H MRI has been used to assess skeletal muscle composition, such as muscle fat-fraction. Additionally, ^23Na imaging and ^31P spectroscopy have provided supplementary information pertaining to tissue viability and metabolic function to evaluate disease even before any measurable change in muscle composition has occurred. This dissertation covers the construction and characterization of radiofrequency (RF) coils and corresponding hardware to enable studies pertaining to breast cancer and DMD. A 32-channel breast array and modified forced-current excitation (FCE) volume coil was constructed for bilateral breast imaging at 7T. Ultimately, coil performance was evaluated based on improvements in SNR and feasibility of accelerated, high spatial resolution imaging. Two double-tuned birdcage coils (^1H/^23Na and ^1H/^31P) were constructed for imaging and spectroscopy at 4.7T of rectus femoris muscles excised from genetically-homologous animal models of DMD, or golden retriever muscular dystrophy (GRMD). Initially, coil performance was evaluated on various phantoms for homogeneity and ability to distinguish between various biological concentrations of sodium and phosphorus. The coils were then used to collect data from a variety of GRMD tissue samples in order to characterize biomarkers corresponding to age/disease progression. Overall, this work has contributed hardware advancements to enable MRI/MRS studies beyond clinically-standard ^1H MRI to assess disease.