Distortion-free high-resolution diffusion MRI

Diffusion MRI provides a unique way to noninvasively observe water diffusion in the tissue. It is routinely applied in both clinical brain and body imaging. Diffusion MRI is able to rapidly diagnose acute cerebral ischemic stroke and has great value in neuroimaging as well as brain white matter disorders diagnosis. Outside of the brain, diffusion MRI plays an important role in oncology imaging. Despite its success in various applications, it is difficult to apply diffusion MRI to locations with magnetic susceptibility variation and challenging to acquire high resolution diffusion MR images for small structures, due to the imperfection of the MRI scanner and limitations of the conventional diffusion MRI technique.
This thesis focused on developing diffusion-prepared sequences for high resolution and distortion-free diffusion MRI. A new MRI sequence called DPsti-TSE was proposed to eliminate the effect of eddy currents in diffusion-prepared sequences. Subsequently, a spiral navigator was integrated into the DPsti-TSE sequence to correct the influence of subtle physiological motion during scanning. To shorten the scanning time, advanced MRI acceleration techniques were applied to these sequences. Finally, state-of-art phase array coils were investigated to boost the scan efficiency of these sequences.
This thesis provided comprehensive solutions to drastically improve image quality as compared to conventional diffusion MRI in various anatomies. The advantages of the proposed methods were demonstrated in multiple experiments and in a clinical study.