Sodium Magnetic Resonance Imaging for Evaluation of Duchenne Muscular Dystrophy

Abstract

Duchenne Muscular Dystrophy (DMD) is a genetic disorder caused by lack of dystrophin, and is characterized by progressive muscle degeneration and weakness. Preliminary magnetic resonance image (MRI) studies have reported that increased tissue sodium concentration (TSC) levels may play a role in the progression of the disease. However, the number of studies reporting this finding are limited. In part, this is due to the fact that 23Na MRI requires the use of customized hardware, pulse sequences and reconstruction techniques. Nonetheless, evaluating abnormal TSC levels may provide valuable information pertaining to disease progression and/or treatment efficacy. To address this need, a custom double-tuned birdcage coil was designed and constructed to evaluate 23Na concentration levels in muscle tissue phantoms using MRI. The coil was constructed with an outer high-pass coil configuration for 1H (200.07 MHz) and an inner low-pass coil configuration for 23Na (52.93 MHz) for a 4.7 T scanner. Bench measurements were taken to evaluate the performance of the coil at both resonant frequencies. The isolation between channels was found to be -25 dB at the 1H frequency and -30.9 dB at the 23Na frequency. The loaded and unloaded quality factors of the coil were evaluated using a phantom that mimicked the loading properties of diseased tissue. The loaded and unloaded quality factors of 1H were 351.1 and 359.9, respectively. The loaded and unloaded quality factors of 23Na were 293.9 and 300.7, respectively. The B1 fields were found to be homogeneous in the operating regions of the coils. Finally, preliminary phantom sodium imaging indicated the ability to distinguish between healthy and diseased 23Na concentration levels.