Model Predictive Control for Real-Time Tumor Motion Compensation in Adaptive Radiotherapy

This paper presents the development and real-time implementation of a control system to automatically adjust the patient support system (PSS) position, thereby compensating for tumor motion caused by respiration and patient movements during radiotherapy treatment. The control scheme utilizes an observer to estimate the PSS state feedback, and a tumor position prediction algorithm to provide the reference for a model predictive controller. The real-time control algorithm was implemented using the Matlab and Simulink environments, with the communication with the clinical PSS performed through the dSPACE real-time system. The controller was shown to be able to position the PSS accurately and was able to track and compensate for organ motion with an accuracy of less than 1 mm in terms of root mean square error, giving rise to dose distributions indistinguishable from a static beam on a fixed target. From a clinical perspective, the increased targeting accuracy will enable an increased dose to the tumor without compromising the surrounding healthy tissues.