Intemational comparison of absorbed dose to water in accelerator photon beams was implemented by star alignment,with the plot laboratory of the BIPM,and the comparison reference value is the absorbed dose to water measured by the graphite calorimeter.According to the respective radiation quality of medical accelerator,national metrology laboratory choose 2 or 3 radiation beams to do the absolute measurement for absorbed dose to water.7 laboratories have completed the comparison,and the results published in the key comparison database.%医用加速器光子水吸收剂量国际比对采用星式比对方式,主导实验室为国际计量局,其石墨量热计复现的水吸收剂量为比对参考值.各国计量实验室依据各自医用加速器辐射质参数,进行2～3个辐射质的水吸收剂量绝对测量,现已完成7个国家的比对工作,比对数据公布在关键比对数据库中.
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