INTRAOPERATIVE 3-DIMENSIONAL ULTRASONOGRAPHY - AN APPROACH TO REGISTER BRAIN SHIFT USING MULTIDIMENSIONAL IMAGE-PROCESSING

Neuronavigation uses the skull as a reference system for transfer of i mage-space data to physical space during brain surgery. This requires a stable spatial relation between the skull and intracranial structure s. However, especially dura opening and preparation for lesion removal causes brain shift. This shift may mislead the surgeon unless preoper atively defined image-space data are corrected for shifting online int raoperatively. Since a real-time modality is required intraoperatively , we propose three-dimensional (3 D) ultrasonography for detection of brain shift. By coupling common ultrasound probes (3.5/6.5 MHz) to a m agnetic digitizer receiver 2 D-ultrasound scans were obtained intraope ratively along with their spatial orientation. 3 D-ultrasonography was achieved by alignment of sequentially obtained 2D-scans. For multimod al matching, preoperative MRI data was segmented for landmarks (cerebr al ventricles, lesion) automatically. The 3 D-ultrasonography data set scanned intraoperatively was contoured and matched with the MRI data set. Intraoperative 3 D-ultrasonography revealed excellent delineation of landmarks in almost real time in six patients studied. Matching of MRI data and intraoperative 3 D-ultrasonography data was successful w ith good correspondence of landmarks. Intraoperative 3 D-ultrasonograp hy is proposed as a promising tool for on-line detection of brain shif t during intracranial operations.