VALIDATION OF A NEW METHOD FOR STEREOTAXIC LOCALIZATION USING MR IMAGING

Magnetic resonance is recognized as potentially the best imaging procedure for localization in stereotactic neurosurgery. However, special difficulties necessitate specific adaptation to localize targets in the stereotactic frame. We developed a new method for stereotactic localization. The MR studies were performed using a 0.5 T imager. Four small boxes filled with CuSO4 solution were inserted into the intracranial holders of a Talairach frame. Using fast sequences, thirty 7-mm thick contiguous sagittal slices and twenty 5-mm thick axial slices enabled us to image the entire brain. The image data were transferred for analysis to an image processing station, including special software to handle stereotactic calculations. The accuracy of the origin of the trihedron and systematic geometrical errors were carefully evaluated using a cubic phantom, and corrective algorithms were applied when needed. Moreover, checks have been designed to detect geometrical distortion due to ferromagnetic artifacts, alterations in gradient calibration, or movements made by the patient. This localization method does not necessitate the use of stereotactic frames and appears to be precise enough for clinical use. Duration of MR examination is not a restricting factor, mainly because the patient can be positioned easily.