Computer-assisted stereotaxic neurosurgery
Description
We have developed a Macintosh II based workstation for stereotaxic neurosurgery planning. Computed Tomography (CT) and Magnetic Resonance Images (MRI) are displayed in the NIH Image environment which was customized to include routines for composite image generation, multiplanar CT image display and Brown-Roberts-Wells stereotaxic frame angle settings calculation. Image data from experimental phantoms and patient studies was used to generate composite images that incorporated the soft tissue detail of MRI images along with the bone definition and coordinate system provided by CT images. Scans from the two modalities were registered globally by calculating a transformation to align the planes of the MRI images along those of CT slices. MRI slices were extracted to correspond to CT slices of interest. Using corresponding landmarks local warping was performed to correct for any remaining misregistration. These composite images along with reformatted CT slices were used to determine the volume of embedded targets in the phantoms and thereby quantify any improvement provided by using these multimodality images. The target volume calculated with the composite images was closer to that physically measured than that obtained with the raw MRI data. Stereotaxic accuracy was not significantly improved with composite images although a qualitative improvement in target definition was seen. This feature was of importance in those patient studies where the lesions were not visible in the CT scans. Volume measurements of intracranial lesions in the patient images were made. The volume calculated with the composite images was found to be consistently less than that with the raw MRI data. Correlation with the phantom experiments would suggest that the composite images were the more accurate of the two