Abstract
Neuronavigation uses the skull as a reference system for transfer of image-space data
to physical space during brain surgery. This requires a stable spatial relation between
the skull and intracranial structures. However, especially dura opening and preparation
for lesion removal causes brain shift. This shift may mislead the surgeon unless preoperatively
defined image-space data are corrected for shifting online intraoperatively. 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 magnetic digitizer receiver 2 D-ultrasound scans were obtained
intraoperatively along with their spatial orientation. 3 D-ultrasonography was achieved
by alignment of sequentially obtained 2 D-scans. For multimodal matching, preoperative
MRI data was segmented for landmarks (cerebral 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 with good correspondence of
landmarks. Intraoperative 3 D-ultrasonography is proposed as a promising tool for
on-line detection of brain shift during intracranial operations.
Key words
3 D - Brain shift - Neuronavigation - Ultrasonography
