Analysis and Design of Higher-Order Motion-Compensated Diffusion Encoding Schemes for In Vivo Cardiac DTI

Introduction: Cardiac diffusion tensor imaging (DTI) [1-3] is increasingly used to characterize myocardial microstructure and myofiber orientation in both normal and diseased hearts. Clinical applications of the technique in humans have been made feasible by employing either STEAM [4] or bipolar diffusion encoding [5] in conjunction with acquisition during the quiescent phase of the cardiac cycle to reduce the effects of motion. However, extension of in vivo cardiac DTI to small animals remains elusive or suboptimal due to the high heart rate, absence of cardiac quiescent phase, and insufficient gradient hardware performance. The present work conducts a systematic analysis of the effects of cardiac motion on diffusion encoding and proposes pulse sequence schemes to minimize them via higher-order motion compensation. The proposed approach is demonstrated by the feasibility of myocardial fiber orientation mapping in live rats, and is expected to benefit in vivo cardiac DTI in humans and other animal species.