Background:The reproducibility of mitral regurgitation (MR) quantification by cardiovascular magnetic resonance (CMR) imaging using different software solutions remains unclear. This research aimed to investigate the reproducibility of MR quantification between two software solutions: MASS (version 2019 EXP, LUMC, Netherlands) and CAAS (version 5.2, Pie Medical Imaging).Methods:CMR data of 35 patients with MR (12 primary MR, 13 mitral valve repair/replacement, and ten secondary MR) was used. Four methods of MR volume quantification were studied, including two 4D-flow CMR methods (MRMVAVand MRJet) and two non-4D-flow techniques (MRStandardand MRLVRV). We conducted within-software and inter-software correlation and agreement analyses.Results:All methods demonstrated significant correlation between the two software solutions: MRStandard(r=0.92, p<0.001), MRLVRV(r=0.95, p<0.001), MRJet(r=0.86, p<0.001), and MRMVAV(r=0.91, p<0.001). Between CAAS and MASS, MRJetand MRMVAV, compared to each of the four methods, were the only methods not to be associated with significant bias.Conclusions:We conclude that 4D-flow CMR methods demonstrate equivalent reproducibility to non-4D-flow methods but greater levels of agreement between software solutions.