Mitsuhiro Nakamura1, Toshiyuki Minemura2, Satoshi Ishikura3, Teiji Nishio4, Yuichiro Narita5, Yasumasa Nishimura6. 1. Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan. Electronic address: m_nkmr@kuhp.kyoto-u.ac.jp. 2. Center for Cancer Control and Information Services, National Cancer Center, Tokyo, Japan. 3. Department of Radiology, Koshigaya Municipal Hospital, Saitama, Japan. 4. Department of Radiation Oncology, Graduate School of Medicine, Hiroshima University, Japan. 5. Department of Oncological Radiation, Aomori Prefectural Central Hospital, Aomori, Japan. 6. Department of Radiation Oncology, Kindai University Faculty of Medicine, Japan.
Abstract
PURPOSE: This study was undertaken to analyze the results of intensity-modulated radiotherapy (IMRT) dosimetry credentialing using a phantom in the Japanese Clinical Oncology Group clinical trials. METHODS: All measurements were performed on-site. The IMRT phantom consisted of a phantom shell and a module. Two types of structures, including a C-shaped planning target volume (PTV) around a column-shaped organ at risk (OAR), were included in the module. Each participating institution was asked to image, plan, and treat the phantom. A prescription dose of 2Gy should cover 95% of the PTV. The plan should limit the maximum doses to the PTV and OAR to less than 110% and 60%, respectively. The pass criteria were ±3% in terms of chamber dosimetry and a difference in profile position ⩽2mm in the high-dose gradient area of film dosimetry. The positional difference was defined as the largest distance between the measured and calculated positions at doses of 60% or 80%. These tolerances were based on the Japanese Society for Radiation Oncology IMRT guidelines. RESULTS: Credentialing was performed on a total of 44 treatment machines in 32 institutions from 2009 to 2015. All differences between measured and planned doses at the measurement points of the PTV were within 3%. The means±standard deviations of the positional differences were 1.0±0.4mm and 0.9±0.3mm without and with the phantom shell, respectively. CONCLUSIONS: The dose differences and positional differences met the desired criteria in all institutions.
PURPOSE: This study was undertaken to analyze the results of intensity-modulated radiotherapy (IMRT) dosimetry credentialing using a phantom in the Japanese Clinical Oncology Group clinical trials. METHODS: All measurements were performed on-site. The IMRT phantom consisted of a phantom shell and a module. Two types of structures, including a C-shaped planning target volume (PTV) around a column-shaped organ at risk (OAR), were included in the module. Each participating institution was asked to image, plan, and treat the phantom. A prescription dose of 2Gy should cover 95% of the PTV. The plan should limit the maximum doses to the PTV and OAR to less than 110% and 60%, respectively. The pass criteria were ±3% in terms of chamber dosimetry and a difference in profile position ⩽2mm in the high-dose gradient area of film dosimetry. The positional difference was defined as the largest distance between the measured and calculated positions at doses of 60% or 80%. These tolerances were based on the Japanese Society for Radiation Oncology IMRT guidelines. RESULTS: Credentialing was performed on a total of 44 treatment machines in 32 institutions from 2009 to 2015. All differences between measured and planned doses at the measurement points of the PTV were within 3%. The means±standard deviations of the positional differences were 1.0±0.4mm and 0.9±0.3mm without and with the phantom shell, respectively. CONCLUSIONS: The dose differences and positional differences met the desired criteria in all institutions.
Authors: Enrica Seravalli; Antonetta C Houweling; Leo Van Battum; Thom A Raaben; Marc Kuik; Jacco A de Pooter; Marion P R Van Gellekom; Jochem Kaas; Wilfred de Vries; Erik A Loeff; Jeroen B Van de Kamer Journal: Phys Imaging Radiat Oncol Date: 2018-02-02