Vessel- and plane-based hepatic segmentation using CT images study on intra-operator variability Ilona Mátéka, László Ruskó* Zoltán Váradi*, András Kriston*, Gyula Molnár*, András Palkó 26 September 2011 University of Szeged, Department of Radiology *GE Hungary Healthcare

Overview I. Purpose –to test clinical usability of research prototype –to measure intra-operator variability of segment separation –Comparison of two approaches: user friendliness, variability, duration Data: –20 contrast cases with pre-defined liver contours –available for public at –6 cases excluded: hepatic vein branches were not visible

Methods –vessel-based: vascular territories of the portal vein - separate visualisation of segment I. –plane-based: the planes should fit to main branches - segment IV. contains segment I. –3 tests with 2 approaches for 14 cases (total 84 runs) Overview II.

manually define main portal vein remove non-portal structures label 8 portal vein branches in 3D view vascular territories of each portal vein branch were computed and displayed Vessel-based protocol

Resulted 3D model

axial images (2D) drawing traces along the main branches of the hepatic vein (left-, middle-, and right), right portal vein, and branches of left portal vein feeding segments II and III Plane-based protocol

frontal viewback 5 smooth surfaces were computed

RunVessel-basedPlane-based 1 st 2 nd 3 rd Case #2

Vessel-based –very difficult to label segmental branches in the right liver: RAPV (V, VIII) and RPPV branches (VI, VII) cannot be identified in most cases (#4, #15, #18, #19) –segment I shows significant variation (as expected) –some variation was due to vessel segmentation: different result from different seeds #3, #16 Plane-based –segment IV is very large in most cases: plane definition may be reconsidered Observations

RunVessel-basedPlane-based 1 st 2 nd 3 rd Case #3

Vessel-based* Average segment size % of total liver volume Plane-based left lobe: 19.2%, left liver: 32.8% right liver: 67.3%, right lobe: 80.9% left lobe: 12.3%, left liver: 32.3% right liver: 67.7%, right lobe: 87.7% *In case of the vessel-based approach segment I. was added to segment IV.

Intra-operator variability % of total liver volume Vessel- based, average 1.8% left lobe: 0.85%, left liver: 1.03% right liver: 2.3%, right lobe: 2.12% Plane-based, average 2.0% left lobe: 1.3%, left liver: 1.63% right liver: 2.3%, right lobe: 2.3% Small difference in intra-operator variability, not significant (statistically)

Vessel-basedAvg.MinMax –PV segmentation48s30s98s –clean PV169s77s396s –label branches179s63s515s –total398s238s702s Plane-based –total201s128s480s Processing time (second) Vessel-based approach takes nearly double time

no significant difference in intra-operator variability processing time: (2x) longer for vessel-based approach: –incorrect PV segmentation –ambiguity of labeling the right PV branches What about precision? –vessel-based approach allows defining segment I. –segment IV. is over-estimated with plane-based approach Conclusions

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