Surgical simulation with computer assisted neurosurgical system

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The aim of the project is to produce 3 dimensional solid model of the patient brain from CT or MR images and to make it possible to perform simulation surgery on it as the preoperative rehearsal. This will enhance neurosurgical accuracy and safeness greatly.We first developed the semi-automated image segmentation that enable to discriminate the area of anatomical structures from CT or MR images. Conventionally, anatomical structures were simply discriminated according to the black and white levels or pixel values, tissue inhomogeniety or noise drifts of the images, however, hamper the strict tissue segmentation. To solve this problem, we analyzed the image characteristics of the region of interest and determined optimal parameters for segmentation. Then, we sequentially applied several image filters to the CT or MR images to obtain tissue contour curves, which were checked immediately by the operator and stored in the image processing computer. The 3 dimensional wire-frame image of the patient head was easily displayd on the screen using tissue contour data. Secondly, we produced the solid model. The contour lines are printed on the wax clay plates with the same thickness as CT or MR slices. The plates are cut along the contour line and compiled to reconstruct the solid model. Finally, we fixed the solid model on the table and shaved with a small spatulas to performed surgical simulation under a neurosurgical navigator, "CANS Navigator". The procedures were recorded with the navigator and replayd at the actual operation.