A model simulator for radiotherapy treatment planning and checking.

For a linear accelerator the direction and orientation of a beam is specified uniquely by a set of gantry, turntable and collimator angles. Sometimes, particularly for 3D planning, it is very difficult for the planner or plan checker to visualize the set-up of the treatment machine from the angles specified for each beam. This note describes a simple line-of-sight model that can be used for planning and checking the radiotherapy geometry prior to simulator verification.