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

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Japanese Journal of Radiology Aims and scope Submit manuscript

Abstract

Purpose

The JSMP01 dosimetry protocol had adopted the provisional 60Co calibration coefficient \(N_{{{\text{D,w,Q}}_{ 0} }}^{{}}\), 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 \(N_{{{\text{D,w,Q}}_{ 0} }}^{{}}\) calibration. In this study, the influence of the calibration shift on the measurement of D w among users was analyzed.

Materials and methods

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.

Results

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 \(N_{{{\text{D,w,Q}}_{ 0} }}^{{}}\) calibration.

Conclusion

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.

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Acknowledgements

We would like to thank our colleagues and staff of the Radiation Therapy Department of Tokyo Metropolitan Hospitals for their cooperation. This work was partially supported by a JSPS Grant-in-Aid for Scientific Research (c) (Multi-year Fund) Number JP26460729.

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Authors and Affiliations

  1. Graduate School of Human Health Sciences, Tokyo Metropolitan University, 7-2-10 Higashiogu, Arakawa-ku, Tokyo, Japan

    Tetsurou Katayose, Hidetoshi Saitoh & Weishan Chang

  2. Chiba Cancer Center, 666-2 Nitona-chou, Chuo-ku, Chiba, Japan

    Tetsurou Katayose

  3. Saitama Medical University International Medical Center, 1397-1 Yamane, Hidaka-shi, Saitama, Japan

    Mitsunobu Igari

  4. Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, 3-18-22 Honkomagome, Bunkyo-ku, Tokyo, Japan

    Shimpei Hashimoto & Mie Morioka

Authors
  1. Tetsurou Katayose
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  2. Hidetoshi Saitoh
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  3. Mitsunobu Igari
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  4. Weishan Chang
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  5. Shimpei Hashimoto
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  6. Mie Morioka
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Corresponding author

Correspondence to Tetsurou Katayose.

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The authors declare no conflict of interest associated with this manuscript.

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Katayose, T., Saitoh, H., Igari, M. et al. Changes in deviation of absorbed dose to water among users by chamber calibration shift. Jpn J Radiol 35, 389–397 (2017). https://doi.org/10.1007/s11604-017-0644-9

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  • DOI: https://doi.org/10.1007/s11604-017-0644-9

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