A collision prevention software tool for complex three-dimensional isocentric set-ups.

During treatment planning it can be difficult to check whether a particular plan is workable, that is it avoids obstructing treatment beams with parts of the patient couch and it avoids collisions between the treatment machine head and the patient couch. To overcome this problem, the trigonometric relationships between the placement of treatment beams and the patient couch are examined. From these relationships a set of useful equations that can be generally applied is derived. The application of these equations practically as a simple (non-graphical) planning tool is described. The resulting tool enables the feasibility of a plan to be checked during treatment planning, and gives guidance as to how a patient could be repositioned to allow the use of a plan when potential beam obstructions are detected, prior to verification of the treatment on a simulator.