Multi-Shot Diffusion Imaging Using Motion Compensation Diffusion Encoding Waveforms and EPI With Keyhole.

Motion-induced shot-to-shot phase variation and strong image aliasing artifacts are common in diffusion weighted imaging (DWI) multi-shot EPI (MS-EPI). Herein, motion-compensated diffusion encoding waveforms were used to minimize shot-to-shot phase variation, and an MS-EPI with Keyhole (MS-EPIK) trajectory was evaluated to mitigate image aliasing. MS-EPI and MS-EPIK with non-motion compensated (M), first order (MM), and first & second order (MMM) motion-compensated diffusion encoding waveforms and a reference single-shot (SS-EPI) acquisition with M diffusion encoding were acquired in vivo at 3T in five volunteers in the brain, liver, and heart. Mean diffusivity (MD) and fraction of anisotropy (FA) were reported in the brain and heart, and the apparent diffusion coefficient (ADC) in the liver. No statistical differences in MD and FA between the SS-EPI, MS-EPIK, and MS-EPI when using the M0M1M2 waveform were found in white and gray matter. In the right liver lobe, statistical differences were found between the ADC of the SS-EPI and MS-EPIK using the M, MM, and MMM waveforms (p < 0.001) and with MS-EPI using MMM (p < 0.001). No differences were observed in MD and FA in the heart between SS-EPI, MS-EPI, and MS-EPIK in the heart. MS-EPIK is less sensitive to image aliasing than MS-EPI approach but remains susceptible to image distortion. Overall, MMM waveforms were found to be the best approach to mitigate shot-to-shot phase variation for MS-EPI in the brain, liver, and heart.