Model-updated image guidance: Initial clinical experiences with gravity-induced brain deformation

Image-guided neurosurgery relies on accurate registration of the patient, t he preoperative image series, and the surgical instruments in the same coor dinate space. Recent clinical reports have documented the magnitude of grav ity-induced brain deformation in the operating room and suggest these level s of tissue motion may compromise the integrity of such systems, We are inv estigating a model-based strategy which exploits the wealth of readily-avai lable preoperative information in conjunction with intraoperatively acquire d data to construct and drive a three dimensional (3-D) computational model which estimates volumetric displacements in order to update the neuronavig ational image set. Using model calculations, the preoperative image databas e can be deformed to generate a more accurate representation of the surgica l focus during an operation, In this paper, we present a preliminary study of four patients that experienced substantial brain deformation from gravit y and correlate cortical shift measurements with model predictions, Additio nally, me illustrate our image deforming algorithm and demonstrate that pre operative image resolution is maintained. Results over the four cases show that the brain shifted, on average, 5.7 mm in the direction of gravity and that model predictions could reduce this misregistration error to an averag e of 1.2 mm.