Fig. 6: 4D-flow cardiovascular magnetic resonance imaging analysis.

Step 1: load the two-chamber and four-chamber cardiovascular magnetic resonance imaging cines (upper panel) and 4D phase-contrast flow and 3D phase-contrast data (lower panel). Step 2: depending on the software tool, perform manual or automated aliasing and velocity offset corrections with the use of the static background tissue. Step 3: an attempt to check for spatial misalignment between the cines and the 4D-flow data should be made because the presence of any major misalignment between them will introduce errors in the quantification of valvular flow. The red arrows indicate the spatial misalignment of both the descending aortic flow (in systole) and the mitral inflow (in diastole). The green arrows indicate how this misalignment has been corrected. Step 4: on both the two-chamber and the four-chamber cines, place two landmark points to mark the valve plane. This marking should be done for the complete cardiac cycle. Software solutions (for example, CAAS software, PIE Medical Imaging, Netherlands) can now automatically track the valve over the complete cardiac cycle. After ensuring the valve is properly tracked, generate a phase-contrast, valvular reformatted plane. Steps 5–6: on the valvular reformatted plane, segment the mitral regurgitant backward flow during left ventricular systole and the forward flow during diastole. The regurgitant plane should be perpendicular to the regurgitant jet. If multiple jets exist, one should make an attempt to evaluate each of them to quantify the total mitral regurgitation (MR). Step 7: quantify valvular forward and backward flow after accounting for the through-plane motion of the valve plane. Similar steps can be used to quantify aortic, tricuspid and pulmonary valvular flows with the use of the 4D-flow data set.