OBJECTIVETo reduce the influence of breathing movement on the location precision of the tumor target in precise radiotherapy for thoraco-abdominal tumors.

METHODSAn inverse tracking system was developed to track the path of the breathing movement of the tumor target via image guiding. With this system, the displacement of the target in a given time period was tracked and quickly transformed in signals that drove the tracking couch to move inversely relative to the tumor target.

CONCLUSIONThis system can effectively reduce the influence of tumor target breath movement during radiotherapy. Compared with other breath movement control methods, this method avoids prolonged exposure time, allows the patient to breathe at ease and shortens the time of CT scanning.