Feasibility Study of Robotics-based Patient Immobilization Device for Real-time Motion Compensation

Abstract

Intrafractional motion of patients, such as respiratory motion during radiation treatment, is an important issue in image-guided radiotherapy. The accuracy of the radiation treatment decreases as the motion range increases. We developed a control system for a robotic patient immobilization system that enables to reduce the range of tumor motion by compensating the tumor motion. Fusion technology, combining robotics and mechatronics, was developed and applied in this study. First, a small-sized prototype was established for use with an industrial miniature robot. The patient immobilization system consisted of an optical tracking system, a robotic couch, a robot controller, and a control program for managing the system components. A multi speed and position control mechanism with three degrees of freedom was designed. The parameters for operating the control system, such as the coordinate transformation parameters and calibration parameters, were measured and evaluated for a prototype device. After developing the control system using the prototype device, a feasibility test on a full-scale patient immobilization system was performed, using a large industrial robot and couch. The performances of both the prototype device and the realistic device were evaluated using a respiratory motion phantom, for several patterns of respiratory motion. For all patterns of motion, the root mean squared error of the corresponding detected motion trajectories were reduced by more than 40%. The proposed system improves the accuracy of the radiation dose delivered to the target and reduces the unwanted irradiation of normal tissue.

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

“…A mechanical slider was used to evaluate tracking algorithms for motion compensation . An industrial robot was combined with a couch plate, and the system’s motion compensation performance was tested . A robotic couch system was designed explicitly for couch tracking and was tested with various patient‐derived tumor motion trajectories .…”

“…Since the robotic couches can move continuously, they have been investigated regarding their use for couch tracking. Several robotic couches have been evaluated for couch tracking . All investigations used different motion trajectories, which makes a comparison of the systems difficult.…”

Simulation and Experimental Studies of Real-Time Motion Compensation Using an Articulated Robotic Manipulator System

“…Mechanical parameters and specifications were summarized in our previous study. 2) To control the robotic couch, we modified the software for measuring the signal using the tracking system so that it sent the couch a displacement signal. The software used the same framework as the tracking system to measure the position of the marker.…”

Analysis of Motion-dependent Clinical Outcome of Tumor Tracking Stereotactic Body Radiotherapy for Prostate Cancer

“… 10 Of these two motion types, inter-fractional movement can be easily corrected in actual treatment by applying one or more image-guidance methods. 11 12 13 14 15 However, correction for intra-fractional prostate motion is rather difficult even with current state-of-the-art techniques because correction for this type of motion requires both constant observation and instant adjustment of radiation targeting.…”