Changes in deviation of absorbed dose to water among users by chamber calibration shift

Abstract

The JSMP01 dosimetry protocol had adopted the provisional 60Co calibration coefficient $$N_{{{\text{D,w,Q}}_{ 0} }}^{{}}$$ N D,w,Q 0 , namely, the product of exposure calibration coefficient N C and conversion coefficient k D,X. After that, the absorbed dose to water D w standard was established, and the JSMP12 protocol adopted the $$N_{{{\text{D,w,Q}}_{ 0} }}^{{}}$$ N D,w,Q 0 calibration. In this study, the influence of the calibration shift on the measurement of D w among users was analyzed. The intercomparison of the D w using an ionization chamber was annually performed by visiting related hospitals. Intercomparison results before and after the calibration shift were analyzed, the deviation of D w among users was re-evaluated, and the cause of deviation was estimated. As a result, the stability of LINAC, calibration of the thermometer and barometer, and collection method of ion recombination were confirmed. The statistical significance of standard deviation of D w was not observed, but that of difference of D w among users was observed between N C and $$N_{{{\text{D,w,Q}}_{ 0} }}^{{}}$$ N D,w,Q 0 calibration. Uncertainty due to chamber-to-chamber variation was reduced by the calibration shift, consequently reducing the uncertainty among users regarding D w. The result also pointed out uncertainty might be reduced by accurate and detailed instructions on the setup of an ionization chamber.

DOI: 10.1007/s11604-017-0644-9

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Cite this paper

@article{Katayose2017ChangesID, title={Changes in deviation of absorbed dose to water among users by chamber calibration shift}, author={Tetsurou Katayose and Hidetoshi Saitoh and Mitsunobu Igari and Weishan Chang and Shimpei Hashimoto and Mie Morioka}, journal={Japanese Journal of Radiology}, year={2017}, volume={35}, pages={389-397} }