Effects of varying diffusion mixing time in ex-vivo cardiac DTI: a comparison of spin echo and stimulated echo sequences

Motivation: Ex-vivo cardiac diffusion MR has improved our understanding of the heart microstructure, depicting in detail the primary helical arrangement of cardiomyocytes in the myocardium. However, accurate depiction of the secondary laminar arrangement of cardiomyocytes (sheetlets) remains challenging. Goal(s): To assess the ability of spin echo (SE) and stimulated echo (STEAM) MR diffusion to characterize sheetlet orientation ex vivo. Approach: Data was acquired with both sequences and varying diffusion mixing times. Voxel-wise diffusion tensor maps were obtained for each dataset. Results: SE and STEAM provide a similar depiction of the primary and secondary cardiomyocyte structures at moderate spatial resolution, with SE offering higher SNR. Impact: High SNR spin-echo based ex-vivo cardiac MR diffusion can provide an accurate characterization of cardiac microstructure and enable high resolution depiction of sheetlet organization in the heart.