Presentation 炭素線治療多施設共同研究J-CROSのQA活動

水野, 秀之  ,  福村, 明史  ,  兼松, 伸幸  ,  米内, 俊祐  ,  白井, 敏之  ,  金井, 達明  ,  遊佐, 顕  ,  矢能, 稔啓  ,  壽賀, 正城  ,  溝田, 学

[Purpose] J-CROS was established in 2014 to obtain clinical evidence through a multi-center clinical trial of carbon-ion radiation therapy. In this trial, it is crucial to assure the uniformity of medical physics issue such as absolute dose used in each facility or treatment planning process. J-CROS QA team was organized in 2015 so as it serves the purpose of enhancing the confidence that the clinical dosimetry is accurate and the facility QA procedures are adequate. [Methods] The initial activity of the team was to settle on QA requirements. Those were as follows, 1. Having established QA program, 2. National protocol based beam calibration and dose specification, 3. Clear specification of RBE model, 4. QA of converting “CT number” to carbon “relative stopping power”, 5. Dose specification to volumes using the standard nomenclature of ICRU reports, 6. Patient anatomical and physiological changes during a fraction or over the course of treatment should be assessed. For the second activity, on-site dose audit was performed for several facility using water phantom. Facilities were requested to obtain CT image with the phantom and make plans as if the phantom is real patient prior to the on-site audit. The isocenter dose was measured by ionization chamber at on-site audit and compared with the calculated dose. [Results] By the end of 2015, on-site audit to 3 facilities were completed and the difference between measured and calculated dose was within ±3% for every facility. [Conclusion] The QA audit was crucial for the success of multi-center clinical trial.

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