Bio-mechanical model of the brain for a per-operative image-guided neuronavigator compensating for 'brain-shift' deformations

摘要

Accurate localization of the target is essential to reduce the morbidity during a brain tumor removal intervention. Image-guided neurosurgery is facing an important issue for large skull openings, with intraoperative changes that remain largely unsolved. In that case, deformations of the brain tissues occur in the course of surgery because of physical and physiological phenomena. As a consequence of this brain-shift, the preoperatively acquired images no longer correspond to reality; the preoperative based neuronavigation is, therefore, strongly compromised by intraoperative brain deformations. Some studies have tried to measure this intraoperative brain-shift. Hastreiter et al. (2004) observed a great variability of the brain-shift ranging up to 24 mm for cortical displacement and exceeding 3 mm for the deep tumor margin; the authors claim for a non-correlation of the brain surface and the deeper structures. Nabavi et al. (2001) state that the continuous dynamic brain-shift processes eVolves differently in distinct brain regions, with a surface shift that occurs throughout surgery (and that the authors attribute to gravity) and with a subsurface shift that mainly occurs during resection (that the authors attribute to the collapse of the resection cavity and to the intra-parenchymal changes).