Motion Planning in Stereotaxic Radiosurgery

Stereotaxic radiosurgery is a procedure which uses a beam of radiation as an ablative surgical instrument to destroy brain tumors. The beam is produced by a linear accelerator which is moved by a jointed mechanism. Radiation is concentrated by crossfiring at the tumor from multiple directions and the amount of energy deposited in normal brain tissues is reduced. Because access to the tumor is obstructed along some directions by critical regions (e.g., brainstem, optic nerves) and most tumors are not shaped like spheres, planning the path of the beam is often difficult and time-consuming. This paper describes a computer-based planner developed to assist the surgeon generate a satisfactory path, given the spatial distribution of the brain tissues obtained with medical imaging. Experimental results with the implemented planner are presented, including a comparison with manually generated paths. According to these results, automatic planning significantly improves energy deposition. It can also shorten the overall treatment, hence reducing the patient’s pain and allowing the radiosurgery equipment to be used for more patients. Stereot axic radiosurgery is an example of so-called “bloodless surgery”. Computer-based planning techniques are expected to facilitate further development of this safer, less painful, and more cost effective type of surgery.