A reference trajectory correction algorithm to improve the tracking accuracy of the robotic phantom system used in the quality assurance of the radiation therapy

Abstract

This paper proposes an algorithm to generate the augmented reference position trajectory for the realtime 3D robotic phantom system which is used in the quality assurance of the radiation therapy. Quality assuarance is the important clinical part of the radiation therapy which ensures the delivery of the prescribed dose to the tumor of the patient. High precision quality assurance can be a difficult task if the tumor exhibits respiratory induced motion inside the body of the patient, as the motion fluctuates along with time and it suffers large inter-patient difference. This paper presents several algorithms to modify and/or correct the reference tumor trajectory of the patient and generate the augmented reference trajectory sequence for the already existing and tuned control system of the robot manipulator to yield high precision tracking to the original tumor motion trajectory. Experimental validation has been carried out for four lung tumor trajectories in the clinical environment using equipments used in the radiotherapy treatment and it has been shown that the clinical demand on the precision of tumor motion tracking has been satisfied for all the four cases.

Implementation of six degree-of-freedom high-precision robotic phantom on commercial industrial robotic manipulator

“…We accordingly use the values available in the in-house controller as the result of control in the rest of the article. Table 3 presents the tracking accuracy metrics, where the quantities aligned with a label V + A corresponds to the RMSEs corresponding to the trajectory generated using the method proposed in our previous work [7]. This table shows that the control sequences synthesized by the RNN-ILC system exhibited superior tracking accuracy relative to the V + A corrected trajectories.…”

“…Since data transmission via network inevitably introduce a lag in the feedback control loop, it might severely degrade tracking accuracy to a continuous reference trajectory. We observed severe tracking performance degradation in our previous work on robotic phantom [7] if we fed raw lung tumor trajectory sequence to the in-house controller. The focus of the present article is accordingly to synthesize an upper level external controller that generates and feeds a set of augmented joint angle trajectories to the in-house controller to guarantee high tracking performance to the original tumor motion trajectory.…”

“…The authors previously developed a three DOF robotic phantom based on the aforementioned commercially available six DOF robotic manipulator [7] that covers only the translational move of a tumor. We have proposed a trajectory correction algorithm using its velocity and acceleration to compensate for the network transmission lag, and showed experimentally that the tracking errors for four lung tumor trajectories fell within the clinical 1mm tolerance.…”

A novel dynamic robotic moving phantom system for patient‐specific quality assurance in real‐time tumor‐tracking radiotherapy

“…The driving accuracy of the dynamic robotic moving phantom was <0.5 mm. 22 Finally, driving signals of each joint of the dynamic robotic moving phantom were sent to the robot controller. Then, these signals in the joint coordinate system were transferred into those in the treatment room coordinate system via forward kinematics calculation, and they were recorded in a log file.…”

“…Second, the 3D coordinate data were interpolated with the third-order spline and upsampled to 5 ms to acquire the reference position in order to drive the dynamic robotic moving phantom. For online compensation of the communication delay between the external controller, the robot controller, and the dynamic robotic moving phantom system and the difference between the reference position and the robot tip position, augmented reference position data were acquired using the velocity and acceleration of the interpolated coordinated data 22. These data were sent to the robot controller via a TCP/IP connection.…”