Dual-phase systolic and diastolic cardiac diffusion tensor imaging using higher order motion compensation spin echo sequences at 300 mT/m gradient strength.

Abstract

Background: Cardiac diffusion tensor imaging (cDTI) provides unique insights into myocardial microstructure and its dynamic changes during the cardiac cycle. However, motion sensitivity remains a major obstacle for spin echo (SE)-based approaches, restricting most implementations to a relatively narrow low-motion window near peak systole.

Purpose: To establish whether higher-order motion-compensated (up to 6th order) diffusion gradients beyond standard second order motion compensation (M₂) on a magnetic resonance imaging (MRI) system with a maximum gradient strength of 300 mT/m improve SE-based cDTI techniques for both systolic and diastolic acquisitions.

Methods: Ten healthy volunteers underwent free-breathing, cardiac-gated SE-cDTI acquisitions in systole and in diastole using diffusion gradients with up to second- (M₂), fourth- (M₄), and sixth-order (M₆) motion compensation. Success rate (percentage of left ventricular voxels with (1.1 < MD < 1.9)  × 10^-3mm²∕s) and diffusion measures including mean diffusivity, fractional anisotropy, helix angle, and secondary eigenvector angle were quantified and compared between both cardiac phases.

Results: Second-order motion compensation was sufficient for systolic cDTI, whereas fourth-order motion compensation was required for successful diastolic acquisitions in all participants. Mean diffusivity values in systole were (1.53 ± 0.06), (1.60 ± 0.07),   and   (1.62 ± 0.06)  × 10^-3mm²∕s for M₂, M₄,   and   M₆ respectively, and in diastole were (2.26 ± 0.67), (1.73 ± 0.19),   and   (1.71 ± 0.12) × 10^-3mm²∕s. No significant differences in cDTI-derived parameters were observed between M₄ and M₆ for systolic and diastolic acquisitions.

Conclusion: This study demonstrates the feasibility of dual-phase SE-based cDTI techniques enabled by 300 mT/m gradients. This method will allow reliable quantification of myocardial microstructural changes between systole and diastole and represents a step towards clinical translation of dynamic cDTI.