Motion prediction and control for patient motion compensation in radiotherapy

This paper summarizes the work carried out at Coventry University on video tracking and patient motion compensation during the MAESTRO European project. A novel combination of motion prediction, couch control and couch nonlinearities compensation was developed and implemented in real time to control an Elekta AB (Publ) ‘Precise’ patient support system or ‘couch'. The reference trajectory was obtained from a video tracking system implemented using LabVIEW. A new anthropomorphic robotic system was used to generate target motions which were captured with a video tracking system that provided a reference to the PSS control system implemented using Matlab® Simulink® and dSPACE. The PSS with its new control system reduced the vertical and longitudinal motion of a surrogate marker located on a robotic arm to less than 1mm RMS and 2mm 95% confidence interval. The motion compensation resulted in significant dosimetric improvements compared to irradiating a moving target. Irradiation of Gafchromic films produced dose distributions with no noticeable differences between fixed target and a motion compensated moving target.