Development of a 1H/31P Spectroscopy Coil Customized for Canine Models of Muscular Dystrophy

Abstract

Duchenne’s Muscular Dystrophy (DMD) is a recessive disorder affecting one in every 3,600 males. The progressive disorder causes lifelong muscle degeneration and eventual death. As no cure is currently available, research in testing treatments for DMD is an area of substantial interest. Animal studies are a necessary and valuable precedent to clinical trials, providing information on experimental treatment response and phenotypic variations that the animal model may present. In evaluating disease progression during treatments, biopsies can provide very accurate results but are often considered unfavorable in DMD animal models due to their invasive nature.

31^P NMR spectroscopy provides a noninvasive means of quantifying concentrations of key muscle metabolites such as phosphocreatine (PCr) and inorganic phosphate (Pi). These metabolites can be used for characterizing disease progression in the Golden Retriever with Muscular Dystrophy (GRMD) canine animal model. While targeted GRMD muscle groups measure between 7 – 15 cm long, depending on the age of the animal model and the stage of the disease progression, commercially available coils capable of 31^P spectroscopy measure approximately 20 x 30 cm. This size difference causes a decrease in sensitivity and thus a decreased signal-to-noise ratio (SNR), motivating the need for a coil customized to interrogate this animal model effectively.

This thesis describes the design and development of a double-tuned 1^H/31^P coil customized for use on canine models of muscular dystrophy using a butterfly/loop configuration. The coil was first developed for a 4.7T Varian Inova scanner and later replicated for a 3T Siemens Verio scanner. Performance of both coils was analyzed using RF bench measurements to test for quality factor and tuning. The capabilities of the 4.7T coil were demonstrated through obtaining proton images and phosphorus spectra of a muscle phantom and canine muscle tissue samples from both control and dystrophin-deficient animal models. The results present a coil capable of obtaining localized and sensitive MR images and spectra using a size and geometry that is optimal for targeted GRMD muscle groups.