Comparison of MRI- and CT-based semiautomated liver segmentation: a validation study.

Abstract

To compare the repeatability, agreement, and efficiency of MRI- and CT-based semiautomated liver segmentation for the assessment of total and subsegmental liver volume. This retrospective study was conducted in 31 subjects who underwent contemporaneous liver MRI and CT. Total and subsegmental liver volumes were segmented from contrast-enhanced 3D gradient-recalled echo MRI sequences and CT images. Semiautomated segmentation was based on variational interpolation and Laplacian mesh optimization. All segmentations were repeated after 2weeks. Manual segmentation of CT images using an active contour tool was used as the reference standard. Repeatability and agreement of the methods were evaluated with intra-class correlation coefficients (ICC) and Bland-Altman analysis. Total interaction time was recorded. Intra-reader ICC were ≥0.987 for MRI and ≥0.995 for CT. Intra-reader repeatability was 30±217ml (bias±1.96 SD) (95% limits of agreement: -187 to 247ml) for MRI and -10±143ml (-153 to 133ml) for CT. Inter-method ICC between semiautomated and manual volumetry were ≥0.995 for MRI and ≥0.986 for CT. Inter-method segmental ICC varied between 0.584 and 0.865 for MRI and between 0.596 and 0.890 for CT. Inter-method agreement was -14±136ml (-150 to 122ml) for MRI and 50±226ml (-176 to 276ml) for CT. Inter-method segmental agreement ranged from 10±47ml (-37 to 57ml) to 2±214ml (-212 to 216ml) for MRI and 9±45ml (-36 to 54ml) to -46±183ml (-229 to 137ml) for CT. Interaction time (mean±SD) was significantly shorter for MRI-based semiautomated segmentation (7.2±0.1min, p<0.001) and for CT-based semiautomated segmentation (6.5±0.2min, p<0.001) than for CT-based manual segmentation (14.5±0.4min). MRI-based semiautomated segmentation provides similar repeatability and agreement to CT-based segmentation for total liver volume.