Vessel- and plane-based hepatic segmentation

using CT imagesstudy on intra-operator variability

Ilona Mátéka, László Ruskó*Zoltán Váradi*, András Kriston*, Gyula Molnár*,

András Palkó26 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 http://sliver07.org/– 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 view back

5 smooth surfaces were computed

Run

Vessel-based Plane-based

1st

2nd

3rd

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

Run

Vessel-based Plane-based

1st

2nd

3rd

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-based Avg. Min Max– PV segmentation 48s 30s 98s– clean PV 169s 77s 396s– label branches 179s 63s 515s– total 398s 238s 702s

• Plane-based– total 201s 128s 480s

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

Thank you for your kind attention!