@misc{oai:repo.qst.go.jp:00076087,
 author = {Fukumura, Akifumi and Mizuno, Hideyuki and Kanematsu, Nobuyuki and Fukumura, Akifumi and Mizuno, Hideyuki and Kanematsu, Nobuyuki},
 month = {Jun},
 note = {BACKGROUND 
There are six carbon-ion radiotherapy (CIRT) facilities in operation and one facility under construction in Japan. Total patients of more than 17,000 have been treated with CIRT all over Japan. NIRS/QST marks the 25th years anniversary of CIRT at HIMAC in 2019. From the viewpoint of public insurance coverage, nationwide multi-institutional clinical trial of CIRT has been started since 2014. [1, 2] To ensure that the results of the trial are meaningful, it is important that the dose reported by one facility is the same as the dose reported by the other facilities. Quality assurance (QA) activities for CIRT were carried out for credentialing facilities to participate in the trial, including dosimetry audit as well as investigations to harmonize medical physics processes among the CIRT facilities in Japan. 

METHODS 
The multi-institutional QA activities for CIRT mainly consist of questionnaires and the following site visit with peer review process. The questionnaires contained 74 items, including beam calibration and verification (6 items), the irradiation system (18 items), treatment planning (27 items), patient immobilization (3 items), patient setup (11 items), and QA (9 items). The site visit included an interview and dosimetry audit, which involved X-ray CT data acquisition, treatment planning, position alignment and ionization chamber dosimetry. For two beam energies of 290 and 400 MeV/u typically, auditors determined absorbed dose to water with ionization chamber measurement based primarily on the IAEA TRS 398. The measured dose was compared with the dose calculated independently by a host facility. The results obtained by the QA activities were reviewed and used for credentialing facilities to participate in the clinical trial. More detailed information on methods of the activities can been seen elsewhere. [3] 

RESULTS 
Table 1 summarizes the dosimetry audit results in the site visit of the QA activities. The average discrepancy between measurements and calculations for absorbed dose to water was 0.6 % with the standard deviation of 1.4 % among the facilities. The maximum absolute value of the discrepancy was 2.7 % within 3 %, which is adopted as optimal limit by the European organization for research and treatment of cancer-radiation oncology group (EORTCROG) for the beam output audit of photon and electron beams [4]. 
 
CONCLUSIONS 
The inter-institutional QA activities including dosimetry audit have shown the consistency of dosimetry among CIRT facilities in Japan. The CIRT has been covered by public insurance for bone and soft tissue sarcoma, head and neck tumor and prostate cancer. The nationwide multiinstitutional clinical trial of CIRT still continues to enlarge the public insurance coverage. 

REFERENCES
 [1]  KOTO, M., et al. Multicenter study of carbon-ion radiation therapy for mucosal melanoma of the head and neck: subanalysis of the japan carbon-ion radiation oncology study group (J-CROS) study (1402 HN). Int J Radiat Oncol Biol Phys. 2017;97:1054– 1060. 
[2]  NOMIYA, T., et al. A multi-institutional analysis of prospective studies of carbon ion radiotherapy for prostate cancer: a report from the Japan Carbon Ion Radiation Oncology Study Group (J-CROS). Radiother Oncol. 2016;121:288–293 
[3]  MIZUNO, H., et al. External dosimetry audit for quality assurance of carbon-ion radiation therapy clinical trials. Radiat Oncol Phys. 2018; DOI: 10.1002/acm2.12465 
[4]  HURKMANS, C.W., et al. Beam output audit results within the EORTC radiation oncology group network. Radiat Oncol. 2016;11:160, International Symposium on Standards, Applications and Quality Assurance in Medical Radiation Dosimetry (IDOS 2019)},
 title = {Quality Assurance Activities for Multi-institutional Clinical Trial of Carbon-ion Radiotherapy in Japan},
 year = {2019}
}