Implementation and incorporation of liver 3-D surface renderings into interactive, image-guided hepatic surgery

In interactive, image-guided surgery, current physical space position in the operating room is displayed on various sets of medical images used for surgical navigation. One useful image display format for image-guided hepatic surgery is liver surface renderings. Deep-seated tumors within the liver can be projected onto the surface of these renderings and provide pertinent information concerning the location and size of metastatic liver tumors. Techniques have been developed by our group to create hepatic surface renderings. An independently implemented variation of the marching cubes algorithm is used on segmented livers to create a triangulated surface, which is displayed using OpenGL, a 3-D graphics and modeling software library. Tumors are segmented separately from the liver so that their colors differ from that of the liver surface. The liver is then rendered slightly transparent so that tumors can be seen within liver and aid surgeons in preoperative planning. The graphical software is also bundled into a dynamic linked library (DLL) and slaved with ORION, our Windows NT based image-guided surgical system. We have tested our graphics DLL on a liver phantom embedded with "tumors". A surface-based registration algorithm was used to map current surgical position onto a transparent phantom rendering that indicates tumor location. The rendering view is updated as surgical position is changed. For minimally invasive procedures, we will use the direct linear transformation and the same surface-based registration technique to map rendered tumors directly onto an endoscopic image. This will be especially useful in localizing deep-seated tumors for ablation and resection procedures.