Simulation of the radiation therapy system for respiratory movement compensation

The goal of the radiation therapy is to give as much dose as possible to the target volume of tissue and avoid giving any dose to a healthy tissue. Advances of the digital control allow performing accurate plans and treatments. Unfortunately, motion compensation during the treatment remains a considerable problem. Currently, combination of the different techniques, such as gating (restricting movement of patient) and periodic emission are used to avoid damaging healthy tissue We are interested in systems that completely compensate respiratory movement (up to certain limit) and start by investigating adequacy of the existing hardware and software platform. We model a radiation therapy system consisting of a HexaPOD couch with 6-degrees movement, a tracking camera, a marker (markers) and a controller. Formal un-timed and timed models were defined, analyzed and found to be insufficient to completely determine adequacy of the system to compensate respiratory motion. We define one-dimensional hybrid model of the system using Open Modelica tool and investigate the model with simple tumor movement trajectories, and based on the results we sketch further development directions.