Collision detection and avoidance during treatment planning.

PURPOSE: To develop computer software that assists the planner avoid potential gantry collisions with the patient or patient support assembly during the treatment planning process. METHODS AND MATERIALS: The approach uses a simulation of the therapy room with a scale model of the treatment machine. Because the dimensions of the machine and patient are known, one can calculate a priori whether any desired therapy field is possible or will result in a collision. To assist the planner, we have developed a graphical interface enabling the accurate visualization of each treatment field configuration within a "room's eye view" treatment planning window. This enables the planner to be aware of, and alleviate any potential collision hazards. To circumvent blind spots in the graphic representation, an analytical software module precomputes whether each update of the gantry or turntable position is safe.
RESULTS: If a collision is detected, the module alerts the planner and suggests collision evasive actions such as either an extended distance treatment or the gantry angle of closest approach.
CONCLUSIONS: The model enables the planner to experiment with unconventional noncoplanar treatment fields, and immediately test their feasibility.