Slice‐specific tracking for free‐breathing diffusion tensor cardiac MRI

Background Diffusion tensor cardiac magnetic resonance (DT‐CMR) imaging has great potential to characterize myocardial microarchitecture. However, its accuracy is limited by respiratory and cardiac motion and long scan times. Here, we develop and evaluate a slice‐specific tracking method to improve the efficiency and accuracy of DT‐CMR acquisition during free breathing. Methods Coronal images were obtained along with signals from a diaphragmatic navigator. Respiratory and slice displacements were obtained from the navigator signals and coronal images, respectively, and these displacements were fitted with a linear model to obtain the slice‐specific tracking factors. This method was evaluated in DT‐CMR examinations of 17 healthy subjects, and the results were compared with those obtained using a fixed tracking factor of 0.6. DT‐CMR with breath‐holding was used for reference. Quantitative and qualitative evaluation methods were used to analyze the performance of the slice‐specific tracking method and the consistency between the obtained diffusion parameters. Results In the study, the slice‐specific tracking factors showed an upward trend from the basal to the apical slice. Residual in‐plane movements were lower in slice‐specific tracking than in fixed‐factor tracking (RMSE: 2.748 ± 1.171 versus 5.983 ± 2.623, P < 0.001). The diffusion parameters obtained using slice‐specific tracking were not significantly different from those obtained from breath‐holding acquisition ( P > 0.05). Conclusion In free‐breathing DT‐CMR imaging, the slice‐specific tracking method reduced misalignment of the acquired slices. The diffusion parameters obtained using this approach were consistent with those obtained with the breath‐holding technique.