MOTION PLANNING IN STEREOTAXIC RADIOSURGERY

Stereotaxic radiosurgery is a procedure that uses a beam of radiation as an ablative surgical instrument to destroy brain tumors (or more ge nerally, brain lesions). The beam is produced by a linear accelerator that is moved by a mechanical gantry. Radiation is concentrated by cro ssfiring at the tumor from multiple directions, to reduce the amount o f energy deposited in healthy tissues. Because access to and exit from the tumor is obstructed along some directions by critical structures (e.g., brain stem, optic nerves), planning the path of the beam is oft en difficult and time-consuming. This paper describes a computer-based planner developed to interactively assist the surgeon generate a sati sfactory treatment, given the spatial distribution of the brain tissue s obtained with medical imaging. This planner has been experimented on using 11 cases previously processed at the Stanford Medical Center. A dosimetric comparison with the manually generated plans for these cas es was carried out. Although still limited, results indicate that auto matic planning can significantly improve energy deposition. It can als o shorten the overall treatment, hence reducing the patient's pain and allowing the radiosurgery equipment to be used for more patients. Ste reotaxic radiosurgery is an example of so-called ''bloodless surgery.' ' Computer-based planning techniques are expected to facilitate furthe r development of this safer, less painful, and more cost effective typ e of surgery.