The ideal couch tracking system—Requirements and evaluation of current systems

Abstract

Introduction: Intrafractional motion can cause substantial uncertainty in precision radiotherapy. Traditionally, the target volume is defined to be sufficiently large to cover the tumor in every position. With the robotic treatment couch, a real-time motion compensation can improve tumor coverage and organ at risk sparing. However, this approach poses additional requirements, which are systematically developed and which allow the ideal robotic couch to be specified.Methods and materials: Data of intrafractional tumor motion were collected and analyzed regarding motion range, frequency, speed, and acceleration. Using this data, ideal couch requirements were formulated. The four robotic couches Protura, Perfect Pitch, RoboCouch, and RPSbase were tested with respect to these requirements. Results:The data collected resulted in maximum speed requirements of 60 mm/s in all directions and maximum accelerations of 80 mm/s 2 in the longitudinal, 60 mm/s 2 in the lateral, and 30 mm/s 2 in the vertical direction. While the two robotic couches RoboCouch and RPSbase completely met the requirements, even these two showed a substantial residual motion (40% of input amplitude), arguably due to their time delays. Conclusion:The requirements for the motion compensation by an ideal couch are formulated and found to be feasible for currently available robotic couches. However, the performance these couches can be improved further regarding the position control if the demanded speed and acceleration are taken into account as well. K E Y W O R D Sintrafractional motion, motion compensation, treatment couch tracking, robotic couch

Robotic Systems in Radiotherapy and Radiosurgery

“…Still, Jöhl et al found acceptable levels of stress in healthy participants [52]. The authors also studied requirements on the accuracy and dynamic properties for robotic couches to enable motion compensation and evaluated several commercially available models [53]. The idea to actively move the patient to align the target with the beam has also been studied in the context of cranial RS using conventional gantry based LINACs [19].…”

Geometric uncertainty analysis of MLC tracking for lung SABR

“…Pommer et al conclusion corroborate the data shown in figure 3 where the AP graphs show a cluster of errors plateauing at approximately 2.5 mm, corresponding to half of a leaf width. As an alternative to implementing thinner leaves, couch tracking (Jöhl et al 2019) could also help reduce residual uncertainties due to leaf width. Ehrbar et al (2017) showed that couch tracking alleviates the impact of the leaf width on the beam-surrogate tracking uncertainty.…”

“…The use of multimodality imaging, such as PET/CT or PET/MRI (Pommer et al 2013), has been shown to improve delineation accuracy. The emergence of automatic or semi-automatic target segmentation (Pommer et al 2013, Ehrbar et al 2017, Jöhl et al 2019 is also showing promise to reduce the inter-observer variability while also potentially saving time for the clinician (Oar et al 2019).…”