Cardio‐respiratory motion‐corrected 3D cardiac water‐fat MRI using model‐based image reconstruction

Purpose Myocardial fat infiltrations are associated with a range of cardiomyopathies. The purpose of this study was to perform cardio‐respiratory motion‐correction for model‐based water‐fat separation to image fatty infiltrations of the heart in a free‐breathing, non‐cardiac‐triggered high‐resolution 3D MRI acquisition. Methods Data were acquired in nine patients using a free‐breathing, non‐cardiac‐triggered high‐resolution 3D Dixon gradient‐echo sequence and radial phase encoding trajectory. Motion correction was combined with a model‐based water‐fat reconstruction approach. Respiratory and cardiac motion models were estimated using a dual‐mode registration algorithm incorporating both motion‐resolved water and fat information. Qualitative comparisons of fat structures were made between 2D clinical routine reference scans and reformatted 3D motion‐corrected images. To evaluate the effect of motion correction the local sharpness of epicardial fat structures was analyzed for motion‐averaged and motion‐corrected fat images. Results The reformatted 3D motion‐corrected reconstructions yielded qualitatively comparable fat structures and fat structure sharpness in the heart as the standard 2D breath‐hold. Respiratory motion correction improved the local sharpness on average by 32% ± 24% with maximum improvements of 81% and cardiac motion correction increased the sharpness further by another 15% ± 11% with maximum increases of 31%. One patient showed a fat infiltration in the myocardium and cardio‐respiratory motion correction was able to improve its visualization in 3D. Conclusion The 3D water‐fat separated cardiac images were acquired during free‐breathing and in a clinically feasible and predictable scan time. Compared to a motion‐averaged reconstruction an increase in sharpness of fat structures by 51% ± 27% using the presented motion correction approach was observed for nine patients.