Cardiac diffusion MRI without motion effects.

The review approach involved evaluating a stimulated echo pulse sequence designed for the beating heart. Investigators utilized two electrocardiogram triggers to synchronize the application of bipolar gradient pulses. The protocol focused on encoding diffusion at a single, brief phase within the cardiac cycle. This duration was strictly maintained at less than 30 ms to avoid phase-related errors. To validate the technique, the team performed tests using a gel phantom undergoing cyclic deformation. They subsequently applied the method to healthy human volunteers to assess in vivo performance. The researchers compared measurements taken at peak contractile velocity with those obtained during myocardial standstill. Finally, they cross-referenced their findings with data from established cardiac imaging protocols to ensure consistency.

Key findings from the literature indicate that the new sequence successfully maps the diffusion tensor without interference from cyclic motion. Measurements in human subjects showed no significant change in myocardial diffusion eigenvalues between peak contractile velocity and end-systole. This stability confirms the technique's independence from the mechanical state of the heart. The acquired images demonstrated strong agreement with registered data from previously validated cardiac diffusion methods. Observations of myocardial sheet orientations revealed a tilt toward the radial direction during systole. Simultaneously, fiber orientations were shown to tilt toward the longitudinal axis. These patterns align qualitatively with earlier invasive studies conducted in canine models. The data demonstrate that the heart can be imaged as if it were frozen at the point of acquisition.

The authors propose that their dual-triggering sequence successfully eliminates artifacts caused by rhythmic heart contractions. Synthesis and implications suggest that this approach allows for accurate diffusion tensor mapping at any point in the cardiac cycle. The researchers claim that myocardial eigenvalues remain stable regardless of whether the heart is contracting or at rest. This finding indicates that the technique effectively isolates diffusion from the influence of contractile velocity. The study demonstrates that observed fiber and sheet dynamics align with previous invasive findings in animal models. These results imply that the method provides a reliable, non-invasive alternative for assessing myocardial architecture in vivo. The authors conclude that the heart can be effectively treated as if it were stationary during the measurement interval. This work confirms the validity of capturing high-fidelity structural data without the need for physical immobilization.