@misc{oai:repo.qst.go.jp:00076101,
 author = {Mizuno, Hideyuki and Fukumura, Akifumi and Yamashita, Wataru and Fukuda, Shigekazu and Takase, Nobuhiro and Mizuno, Hideyuki and Fukumura, Akifumi and Yamashita, Wataru and Fukuda, Shigekazu and Takase, Nobuhiro},
 month = {Jun},
 note = {BACKGROUND
In 2007, a postal dose audit of an external radiation therapy unit was initiated in Japan using radiophotoluminescent glass dosimeter (RPLD). The methodology developed by National Institute of Radiological Sciences and operated by Association for Nuclear Technology in Medicine. Audit is performed according to the request of the hospitals and the fee is about 700 € for 4 X-ray beam conditions.  
METHODS
RPLD and solid phantom are used in the audit. RPLD is silver activated phosphate glass and the density is 2.61 g/cm3. RPLD characteristics such as repeatable readout and negligible fading effect is suitable for the postal dose audit. Audit began with a reference condition and expanded its application to beams of different field size and wedged beams in 2010. In addition, in 2016, the modern type treatment units such as a flattening filter free linear accelerator, Tomotherapy unit, and Cyberknife unit could also be applied to audit.
RESULTS
By the end of the Oct. 2017, 4,579 beams were checked.  Regarding the reference condition (2,326 beams), mean and standard deviation of the ratio of the measured dose to the intended dose (deviation) were +0.3% and +1.1%, respectively. This result indicates that the audit system was maintained well, and the dose was successfully evaluated. Regarding the variation in audit results, 99.9% of the beams was within tolerance level (Deviation should be within the 5%). However, 5 beams exceeded the tolerance level of 5%. In most cases, there was a clear mistake in the contents of the entry sheet of the audit. Hearing was done to the hospitals to clarify the cause, and in almost every case the cause was identified. 
CONCLUSIONS
This activity has certainly improved the quality of the radiation therapy in Japan. More efforts are underway, such as application to electron beams or intensity modulated radiation therapy., International Symposium on Standards, Applications and Quality Assurance in Medical Radiation Dosimetry (IDOS 2019)},
 title = {10 years RPLD postal dose audits for radiotherapy in Japan},
 year = {2019}
}