Virtual operation planning in liver surgery

The operability of a liver tumour depends on its three-dimensional relation to the intrahepatic vascular trees which define autonomously functioning l iver (sub-)segments. The aim of our study was to establish a computer-based three-dimensional volumetric operation planning system for the liver. Meth ods: Using data from routine helical CT scans the three tissue subclasses o f liver parenchyma, liver vessels and liver tumour were segmented semiautom atically. A dedicated segmenting tool was established using region growing algorithms in combination with an "intelligent" border finder. Visualisatio n is performed by the "Heidelberg Raytracer". The vascular trees are visual ised as 3D graphs. Pseudo-connections between portal and hepatic venous tre es are separated automatically. Security margins are calculated and the sys tem presents a virtual resection proposal. Results: The 3D anatomy of the l iver can be visualised in high quality resulting in good depth perception. Security margins are demonstrated. Dependent Fiver parenchyma can be recogn ised automatically on the basis of the vascular trees. The system offers a individualised resection proposal including the tumour, security margin and dependent liver parenchyma. Conclusion: Three-dimensional presentation of the individual liver anatomy of a given patient facilitates the perception of the pathology. Virtual reality combined with artifical intelligence allo ws calculation of complete resection protocols, which can be quantified and modified interactively. This will make operation planning more objective; patient selection may be improved, and in cases of difficult tumour localis ation different resection strategies may be tested. Thus virtual reality in liver surgery will improve teaching, surgical training and planning. It ma y lead to improved surgical care.