Intraoperative ultrasound imaging for the detection and correction of tissue movement in image-guided neurosurgery

Pre-operative image based image guided neurosurgery (IGNS) systems involve the mapping of intraoperative real world coordinates and trajectories to one or more preoperative image data spaces. This is accomplished using a rigid body transformation from patient to image coordinate systems, which is usually obtained by identifying external landmarks on the patient and on the images, and employing a least squares minimization technique. The validity of the rigid body transformation relies on the assumption that the patient and localizing device form a completely rigid body for the duration of the procedure. It has been observed that the brain tissue moves significantly within the skull, particularly after large open craniotomies, violating this assumption of rigidity.; A surgical guidance system has been developed that combines pre-operative image information (e.g. MRI or CT) and intraoperative ultrasound imaging to detect brain tissue deformation during IGNS. The system includes hardware and software to track the ultrasound transducer during image acquisition, and visualization software to view the live ultrasound and co-planar MRI images. The software includes tools to delineate structures in either modality and overlay these images on one another, and warp the preoperative image based on the delineated structures.; The thesis includes a discussion of techniques, instruments and results, using a novel calibration tool and a multi-modality deformable phantom. Finally, the clinical experience from the use of this system in the operating room are presented.