会議発表論文 An individual calibration system for electrometer and ionization chamber of radiotherapy dosimeters

Takase, Nobuharu  ,  Sakata, Suoh  ,  Endo, Masahiro  ,  Narita, Katuhisa  ,  Yamasita, Wataru  ,  Hoteida, Masahiro  ,  Sasaki, Yosuke  ,  Okuyama, Hiroaki  ,  Ushiroda, Tota  ,  Mizuno, Hideyuki  ,  Fukumura, Akifumi

37 ( Sup.3 )  , p.167 , 2018-03 , 株式会社国際文献社(一般社団法人日本医学物理学会)
ISSN:1345-5362
内容記述
Purpose: Since 2004, Association for Nuclear Technology in Medicine (ANTM) has been carrying out a calibration service for radiotherapy dosimeters, as the unique secondary standard dosimeter laboratory in Japanese external radiotherapy field. The service provides an absorbed dose to water calibration factor to a set of chamber and electrometer, at a single electrometer range.Recently, the authors have established a charge calibration system for electrometer to provide calibration factor at each electrometer range. The new system allows chamber calibration without customer's own electrometers.Method: We assembled a reference standard measurement device of charge with capacitors and a DC voltmeter. Those are traceable to the corresponding national measurement standard. A customer’s reference class chamber can be calibrated with the best relative expanded uncertainty of 1% (k=2) with the new system. Result: We compared the results of electrometer with the calibration factors given in the ADCL’s certificate with A2LA accredited symbol. The calibration factors obtained be the authors and ADCL agreed within the relative expanded uncertainties. The results of ionization chambers also were compared with the calibration factors given in the NMIJ test report. Both factors agreed within relative expanded uncertainties.Conclusion: New calibration system established by the authors has been verified by the two experiments. The individual calibration system for electrometer and chamber would simplify the quality control method of reference dosimeters at radiotherapy facilities.

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