In Vivo Diffusion MRI of the Human Heart Using a 300 Mt/m Gradient System

Purpose: This work reports for the first time on the implementation and application of cardiac diffusion-weighted MRI on a Connectom MR scanner with a maximum gradient strength of 300 mT/m. It evaluates the benefits of the increased gradient performance for the investigation of the myocardial microstructure. Methods: Cardiac diffusion-weighted imaging (DWI) experiments were performed on 10 healthy volunteers using a spin-echo sequence with up to second- and third-order motion compensation (M-2 and M-3) and b = 100, 450, and 1000 s/mm(2) (twice the b(max) commonly used on clinical scanners). Mean diffusivity (MD), fractional anisotropy (FA), helix angle (HA), and secondary eigenvector angle (E2A) were calculated for b = [100, 450] s/mm(2) and b = [100, 1000] s/mm(2) for both M-2 and M-3. Results: The MD values with M-3 are slightly higher than with M-2 with Delta MD = 0.05 +/- 0.05[x10(-3)mm(2)/s](p = 4e-5) for b(max) = 450s/mm(2) and Delta MD = 0.03 +/- 0.03[x10-3mm(2)/s](p = 4e-4) for b(max) = 1000s/mm(2). A reduction in MD is observed by increasing the b(max) from 450 to 1000 s/mm(2) (Delta MD = 0.06 +/- 0.04[x10(-3)mm(2)/s](p = 1.6e-9) for M-2 and Delta MD = 0.08 +/- 0.05[x10(-3)mm(2)/s](p = 1e-9) for M-3 ). The difference between FA, E2A, and HA was not significant in different schemes (p>0.05). Conclusion: This work demonstrates cardiac DWI in vivo with higher b-value and higher order of motion compensated diffusion gradient waveforms than is commonly used. Increasing the motion compensation order from M-2 to M-3 and the maximum b-value from 450 to 1000 s/mm(2 )affected the MD values but FA and the angular metrics (HA and E2A) remained unchanged. Our work paves the way for cardiac DWI on the next-generation MR scanners with high-performance gradient systems.