Creating hemodynamic atlases of cardiac 4D flow MRI

Hemodynamic atlases can add to the pathophysiological understanding of cardiac diseases. This study proposes a method to create hemodynamic atlases using 4D Flow magnetic resonance imaging (MRI). The method is demonstrated for kinetic energy (KE) and helicity density (H_d ).

Thirteen healthy subjects underwent 4D Flow MRI at 3T. Phase-contrast magnetic resonance cardioangiographies (PC-MRCAs) and an average heart were created and segmented. The PC-MRCAs, KE, and H_d were nonrigidly registered to the average heart to create atlases. The method was compared with 1) rigid, 2) affine registration of the PC-MRCAs, and 3) affine registration of segmentations. The peak and mean KE and H_d before and after registration were calculated to evaluate interpolation error due to nonrigid registration.

The segmentations deformed using nonrigid registration overlapped (median: 92.3%) more than rigid (23.1%, P < 0.001), and affine registration of PC-MRCAs (38.5%, P < 0.001) and affine registration of segmentations (61.5%, P < 0.001). The peak KE was 4.9 mJ using the proposed method and affine registration of segmentations (P = 0.91), 3.5 mJ using rigid registration (P < 0.001), and 4.2 mJ using affine registration of the PC-MRCAs (P < 0.001). The mean KE was 1.1 mJ using the proposed method, 0.8 mJ using rigid registration (P < 0.001), 0.9 mJ using affine registration of the PC-MRCAs (P < 0.001), and 1.0 mJ using affine registration of segmentations (P = 0.028). The interpolation error was 5.2 ± 2.6% at mid-systole, 2.8 ± 3.8% at early diastole for peak KE; 9.6 ± 9.3% at mid-systole, 4.0 ± 4.6% at early diastole, and 4.9 ± 4.6% at late diastole for peak H_d . The mean KE and H_d were not affected by interpolation.

Hemodynamic atlases can be obtained with minimal user interaction using nonrigid registration of 4D Flow MRI.

2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1389-1399.