Multiplexed Sensitivity Encoding of Multi-Shot Diffusion-Weighted Echo Planar MRI at 0.5 Tesla for Cholesteatoma Imaging

Abstract

Cholesteatoma is an abnormal skin mass in the middle ear requiring surgical excision, and accurate post-surgical imaging is of interest to avoid repeat surgeries. MRI suffers from susceptibility-induced field gradients at air-bone interfaces in the auditory canal, resulting in geometric distortion and signal pile-up. Multi-shot diffusion-weighted echo-planar imaging (ms-DW-EPI) at 0.5 T may reduce distortion, but requires motion correction. Multiplexed sensitivity encoding (MUSE) estimates intra-shot phase errors from motion, but requires sufficient signal to perform the correction. It is unknown whether ms-DW-EPI at 0.5 T provides sufficient signal to perform MUSE. In this work, a MUSE reconstruction pipeline was designed and optimized. The engineering design process leading to an optimized system for reconstructing patient images is discussed. The resulting images demonstrated qualitatively reduced motion artifact compared to images reconstructed without MUSE and was statistically supported, confirming the hypothesis. This supported further exploration into imaging cholesteatoma with ms-DW-EPI at 0.5 T.