Combined patient motion compensation and dose rate variation to improve radiotherapy treatment dosimetric accuracy

This paper demonstrates that using a novel combination of motion prediction algorithm, couch control system and couch nonlinearities compensator it is possible to realise a `breathing couch´ with a standard Elekta patient support system (PSS). The couch has been shown to be able to reduce the vertical and longitudinal motion of a surrogate located on a robotic arm to less than 1mm RMS and 2mm 95%CI. The irradiation of a moving target was compared to that of a fixed target and a moving target which motion is compensated by the PSS. No noticeable differences were observed between the films obtained for the fixed and the vertical & longitudinal compensated motions. When tracking is combined with dose rate adaption further improvement can be obtained without significantly increasing the treatment time.