Intraoperative US in interactive image-guided neurosurgery

Tissue movement can be a significant source of error in image-guided neurosurgery. A surgical guidance system that incorporates preoperative image information (eg, magnetic resonance [MR] imaging data) and intraoperative ultrasound (US) allows detection of tissue deformation during neurosurgery. An interactive image overlap tool allows a region of interest (ROI) to be defined and permits the operator to move the ROI over the MR or US image and overlay the associated image (US or MR) within the ROI, The system can be validated with a deformable multimodality phantom, Before deformation of the phantom, good agreement between the MR imaging and US data overlay confirms proper registration of the MR and US images; after deformation, the overlay demonstrates significant distortion of ventricles and movement of simulated blood vessels. Intraoperatively, this information helps establish the orientation of the US image being displayed by providing an oblique MR image that coincides with the live US view. The superior anatomic display of MR imaging also helps the surgeon interpret the corresponding US images, Finally, the system enables the surgeon to evaluate the patient-MR image registration by comparing structures on the MR images and live US images and using the overlay tool to visualize discrepancies.