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

Purpose To compare the repeatability, agreement, and efficiency of MRI- and CT-based semiautomated liver segmentation for the assessment of total and subsegmental liver volume. Methods 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 2 weeks. 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. Results Intra-reader ICC were ≥0.987 for MRI and ≥0.995 for CT. Intra-reader repeatability was 30 ± 217 ml (bias ± 1.96 SD) (95% limits of agreement: −187 to 247 ml) for MRI and −10 ± 143 ml (−153 to 133 ml) 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 ± 136 ml (−150 to 122 ml) for MRI and 50 ± 226 ml (−176 to 276 ml) for CT. Inter-method segmental agreement ranged from 10 ± 47 ml (−37 to 57 ml) to 2 ± 214 ml (−212 to 216 ml) for MRI and 9 ± 45 ml (−36 to 54 ml) to −46 ± 183 ml (−229 to 137 ml) for CT. Interaction time (mean ± SD) was significantly shorter for MRI-based semiautomated segmentation (7.2 ± 0.1 min, p < 0.001) and for CT-based semiautomated segmentation (6.5 ± 0.2 min, p < 0.001) than for CT-based manual segmentation (14.5 ± 0.4 min). Conclusion MRI-based semiautomated segmentation provides similar repeatability and agreement to CT-based segmentation for total liver volume.