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ORIGINAL RESEARCH article

Front. Phys.
Sec. Medical Physics and Imaging
Volume 12 - 2024 | doi: 10.3389/fphy.2024.1395997
This article is part of the Research Topic

Physical, Biological, Clinical, and Methodological Advances in Particle Therapy

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A Nine-Degree-of-Freedom optimization-based method to evaluate the isocenter coincidence of the treatment beams and image system of a medical accelerator Provisionally Accepted

Yun Zhou1, 2 Jian Qiao3, 4, 5, 6 Nan Yan1, 2 Liyan Dai7 Yuehu Pu8*
  • 1Shanghai Institute of Applied Physics, Chinese Academy of Sciences (CAS), China
  • 2University of Chinese Academy of Sciences, China
  • 3Department of Radiation Oncology, Shanghai Cancer Center, Fudan University, China
  • 4Department of Oncology, Shanghai Medical College, Fudan University, China
  • 5Shanghai Clinical Research Center for Radiation Oncology, China
  • 6Shanghai Key Laboratory of Radiation Oncology, China
  • 7Department of radiation oncology, Renji hospital affiliated to Shanghai Jiao Tong University School of Medicine, China
  • 8Medical Equipment Innovation Research Center, West China School of Medicine, Med+X Center for Manufacturing, West China Hospital, Sichuan University, China

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Medical accelerators have been widely used in tumor radiation therapy. Accurate isocenter coincidence between treatment beams and imaging systems is critical for image-guided radiation therapy (IGRT). We propose a method utilizing a phantom with marker spheres to detect the Nine Degrees of Freedom (9-DOF) in the system's geometric model to assess isocenter coincidence between the treatment beams and the kV cone-beam computed tomography (CBCT). The phantom was initially aligned with the accelerator. Subsequently, the projections of the treatment and CBCT beams' were acquired separately with full gantry rotation. By analyzing the marker spheres' position in both the treatment beam and CBCT beam projections, the 9-DOF parameters were calculated. A comparison with a Winston-Lutz-based system was performed. Then, the analysis revealed imprecise circular trajectories with noticeable random deviations in the rotations of both the treatment beams and CBCT. The isocenter deviations for the treatment beams and CBCT were 0.18 mm (X), -0.49 mm (Y), and -0.35 mm (Z) after trajectories fitting, respectively. The rotational planes of the two systems exhibited a pinch angle of 0.0235°. This proposed method offers a quantitative

Keywords: Radiation therapy (radiotherapy), medical accelerator, isocenter coincidence, Quality Assurance, cone-beam computed tomography (CBCT)

Received: 05 Mar 2024; Accepted: 20 May 2024.

Copyright: © 2024 Zhou, Qiao, Yan, Dai and Pu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mx. Yuehu Pu, Medical Equipment Innovation Research Center, West China School of Medicine, Med+X Center for Manufacturing, West China Hospital, Sichuan University, Chengdu, Sichuan Province, China