[Basic study on MRI guided stereotaxic surgery]

In 1987, we started MRI guided stereotaxic surgery using BRW-MRI apparatus. As distortion of image had been noted around the periphery of MRI due to the characteristic static magnetic field, we examined accuracy of data before clinical application. The MRI machine was a MRT-15A, 0.15 Tesla resistive type made by Toshiba. The stereotaxic apparatus consisted of a head ring, which was fixed to the patient's head, a cubical localizer frame which was attached to the head ring for the scanning phase, and a programmed computer. The localizer frame had multitubular channels, which could be fixed and drained easily with whatever paramagnetic fluid was desired. Since the beginning of our use of the instrument, we have used petroleum jelly. This material produced sufficient localizer image for us to fully determine any MRI scan plane. Once the MRI scan target had been identified, it could be approached stereotaxically in a same way as was done in the CT-related one. In the examination, at first, we studied the MRI image of a grid phantom, or the localizer frame placed on the center of the magnetic field. In the MRI, distortion of the image was seen only at the periphery of the Z axis. Secondly, we calculated the three-dimensional coordinates of the center of tumors in axial, coronal and sagittal images for correlation. But, the target values did not differ by over 5.1 mm. Therefore we concluded that the distortion of the image had minimum effect on surgery. Thirteen surgical operations were performed for brain tumors. Among these surgical interventions biopsy alone was performed in 8 cases, and biopsy combined with brachytherapy was performed in 5 cases.(ABSTRACT TRUNCATED AT 250 WORDS)