Fig. 2

4D flow CMR jet tracking analysis for direct MR quantification. LA blood flow is visualized throughout systole to look for MR. For each timeframe with MR, an MVPR reformatted plane (dashed line) is positioned at the peak velocity of the MR jet, oriented orthogonal (dashed arrow) to the jet, and contoured to capture the cross-section of the jet and calculate the regurgitant flow rate (Fig. 1). The resulting regurgitant flow rate curve is spline-interpolated and integrated over the MR jet period to calculate MR volume. The MPR planes dynamically track and adapt to the jet direction over systole. In this example, a 52 year-old male with hypertrophic cardiomyopathy (HCM) (maximal wall thickness (MWT) 2.4 cm) and a typical mid-to-late systolic posterolateral MR jet is depicted with an MR volume of 16 mL, consistent with mild MR (see Additional file 1: Video S1)