Prog Med Phys.  2016 Sep;27(3):117-124. 10.14316/pmp.2016.27.3.117.

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

Affiliations
  • 1Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea.
  • 2Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. cho.byungchul@gmail.com bcho@amc.seoul.kr

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.

Keyword

Robotics; Mechatronics; Patient immobilizer; Respiratory motion; SBRT

MeSH Terms

Calibration
Compensation and Redress*
Feasibility Studies*
Freedom
Humans
Immobilization*
Radiotherapy, Image-Guided
Robotics

Figure

  • Fig. 1 (a) Prototype of the patient immobilization system consisting of a robotic arm, a couch, a robot controller, an optical tracker, and a camera. (b) Schematic of the motion compensation system.

  • Fig. 2 Real-scale patient immobilization system for evaluating the motion compensation performance with respect to the respiration-associated motion.

  • Fig. 3 (a) Screenshot of the in-house motion detection and control program running on the system control PC. (b) Algorithm flow chart of the developed motion compensation system. Pc(ti) and Pp(ti) are 3D positions of the marker on the couch and the marker on the motion phantom at time ti. R is the coordinate transformation matrix, from the optical tracker system of coordinates to the robot system of coordinates.

  • Fig. 4 3D position data measured by the optical tracker, for markers attached to the motion phantom and couch. The typical-slow respiratory motion pattern was considered here. (a) Results obtained for the prototype system. (b) Results obtained for the real-scale system. The motion compensation was initiated about halfway into the measurement period.


Cited by  2 articles

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Hoon Sik Choi, Ki Mun Kang, Bae Kwon Jeong, Jin Ho Song, Yun Hee Lee, In Bong Ha, Sung Chul Kam, Jeong Seok Hwa, Jae Seog Hyun, Jungmo Do, Dong Hyeok Jeong, Hojin Jeong
J Korean Med Sci. 2018;33(14):.    doi: 10.3346/jkms.2018.33.e107.

Simulation and Experimental Studies of Real-Time Motion Compensation Using an Articulated Robotic Manipulator System
Minsik Lee, Min-Seok Cho, Hoyeon Lee, Hyekyun Chung, Byungchul Cho
Prog Med Phys. 2017;28(4):171-180.    doi: 10.14316/pmp.2017.28.4.171.


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