Reproducibility and reliability of flow quantification using CMR 2D-phase contrast and 4D-Flow in secondary mitral valve regurgitation

Figures

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  Fig. 1. Illustration of MVR quantification methods. 2D-PCstandard, CMR flow gold standard (Left Ventricle Stroke Volume [LV SV]– Aortic Forward Flow Volume derived from 2D-PC plane [AoPC]); 2D-PCMVAAo, Forward Flow through Mitral Valve (MVPC) - AoPC; 2D-PCMVdirect, directly quantifying flow through Mitral Valve (Backward flow through Mitral Valve [RegurgVolMV]); Volumetric (LV SV– Right Ventricle Stroke Volume [RV SV]); 4D-flowstandard, similar to 2D-PCstandard using 4D-flow sequence instead of 2D-PC (LV SV– AoPC); 4D-flowMVAAo, similar to 2D-PCMVAAo using 4D-flow sequence instead of 2D-PC (MVPC– AoPC); 4D-flowMVdirect, directly quantifying flow through Mitral Valve (Backward flow through Mitral Valve [RegurgVolMV]); AoPC, Aortic Forward Flow (OutflowAAo); MVPC, Mitral Valve Forward Flow (InflowMV); EDV, End Diastolic Volume; ESV, End Systolic Volume

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  Fig. 2. Box plots of Mitral Valve Regurgitation (MVR) volumes measured using various CMR flow quantification methods. Measurements were taken with seven distinct methods, based on a cohort comprising 26 patients with 2D-PC data, of whom 15 patients also underwent 4D-flow acquisition. Each method was analyzed by two readers: once by reader A and twice by the same reader (B1 and B2). Outliers (Z-score > 2) were removed from the data to enhance clarity. Each method is illustrated with its corresponding box plot, with individual measurement points overlayed in red

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  Fig. 3. Heatmap of Intra-Reader and Inter-Reader Intraclass Correlation Coefficient (ICC) values for MVR volume measurements across various CMR flow quantification methods. The analysis includes the same 15 patients who underwent both 2D-PC and 4D-flow acquisitions. Each cell displays the ICC value, with p-values annotated below. Methods include both 2D and 4D-flow measurements, as well as Volumetric analysis, comparing reliability between repeated measurements by the same reader (Intra-Reader) and measurements by different readers (Inter-Reader). The color scale represents ICC values, with darker red colors indicating stronger reliability and darker blue colors indicating weaker reliability. (ICC > = 0.9, excellent reliability; ICC = 0.75–0.9, good reliability; ICC = 0.5–0.75, moderate reliability; ICC < 0.5, poor reliability.)

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  Fig. 4. Bland-Altman plots comparing inter- and intra-reader measurements of MVR volumes across various CMR flow quantification methods. The analysis includes 26 patients for 2D-PC methods and 15 patients for 4D-flow methods. Each plot displays the mean of two measurements on the x-axis and the difference between them on the y-axis, with limits set from 0 to 80 on the x-axis and − 80 to + 80 on the y-axis. Horizontal dashed lines indicate the mean difference (gray) and the limits of agreement (± 1.96 SD, red). Inter-reader plots (comparing two different readers) are shown first for each method, followed by intra-reader plots (comparing repeated measurements by the same reader), providing insights into the consistency of measurements across and within readers for each quantification method

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  Fig. 5. MVR severity classification of mitral valve regurgitation (MVR) across various CMR flow quantification methods. The stacked bar chart shows the distribution of a subset of cases, the patients with both 2D-PC and 4D-flow acquisitions (n = 15), classified as Mild, Moderate, or Severe for each method. Percentages within the bars indicate the relative contribution of each severity category, providing a detailed comparison of the classification outcomes for different measurement techniques