ACCURATE FRAMELESS REGISTRATION OF MR AND CT IMAGES OF THE HEAD - APPLICATIONS IN PLANNING SURGERY AND RADIATION-THERAPY

PURPOSE: To evaluate the feasibility and efficacy of a three-dimension al image registration technique for planning skull base surgery, perfo rming frameless image registration for stereotaxic neurosurgery, and s taging nasopharyngeal carcinoma. MATERIALS AND METHODS: Computed tomog raphic (CT) and magnetic resonance (MR) images from 35 patients were r egistered by identifying 12-16 homologous landmarks with each modality . Images were displayed as overlaid sections or rendered three-dimensi onal scenes. The clarity of the combined images from 15 patients under going skull base surgery was compared with that of the conventional di splays. RESULTS: Images were combined for three applications, with an accuracy of 1-2 mm. For the 15 patients undergoing skull base surgery, the combined images were significantly better at depicting the relati onship between bone and lesion than conventional display (P < .01). CO NCLUSION: MR and CT images of the head can be accurately registered wi thout using external markers or substantially altering image acquisiti on protocols. The resulting images can show the radiologic information more clearly than conventional viewing.