Real-time Motion Management for Robotic Treatment Couch in Proton Therapy System

Abstract Background: In proton therapy, robotic couch was used for patient positioning to achieve high precision in cancer treatment. However, no studies have focused on the real-time motion management system (MMS) for the robotic couch. This study was to develop the MMS and verify its feasibility. Methods: A real-time MMS was set up with a robotic couch, an NDI Vega optical tracking system, a Special Measurement Tool (SMT) and the developed software. A Leica laser tracker was adopted to verify the accuracy of the tests in this study. The stability and accuracy of the SMT in NDI Vega system were verified to guarantee the reliability of the results. The coordinate transformation was used to unify the measurement. 83 points inside the treatment volume were applied to verify the accuracy of the MMS, with the comparison of results measured by the laser tracker. The synchronism of the SMT in the MMS and Patient Positioning System (PPS) based on the reciprocating motion along axis z was tested to obtain the maximum time delay. Trajectory tracking was performed with different payloads on the couch top. Results: The Means and Standard Deviation (SD) of the stability of the SMT in NDI tracking system on the axis x, y, z, and Rx, Ry, Rz were 0.005 ± 0.004 mm, 0.013 ± 0.005 mm, 0.014 ± 0.005 mm, 0.010 ± 0.003º, 0.013 ± 0.005º, 0.008 ± 0.007º, respectively. For the MMS, the means ± SD along axis x, y, z were 0.24 ± 0.09 mm (0.12 ± 0.03 mm With Laser Tracker (WLT)), 0.31 ± 0.12 mm (0.10 ± 0.03 mm WLT), 0.18 ± 0.06 mm (0.14 ± 0.05 mm WLT), respectively. The max time delay was about 110 ms, with a 60 s of motion tracking. Trajectories tracking showed the real-time graphical traces of the SMT in NDI Vega and Room Coordinate system, and the combined curves by using the coordinate transformation. Conclusions: A real-time MMS was developed and verified with the accuracy of submillimeter in this study. The results demonstrated the feasibility of potential applications based on real-time motion capturing and monitoring.