| Zhao Xipeng,Yue Baorong,Xu Hui.Determination and optimization of radition quality of calibration system for mammography dosimeters in IAEA/WHO secondary standard dosimetry laboratory[J].Chinese Journal of Radiological Medicine and Protection,2021,41(10):772-777 |
| Determination and optimization of radition quality of calibration system for mammography dosimeters in IAEA/WHO secondary standard dosimetry laboratory |
| Received:December 14, 2020 |
| DOI：10.3760/cma.j.issn.0254-5098.2021.10.009 |
| KeyWords:Calibration system for mammography dosimeters Tube voltage HVL1 Aluminum sheet thickness |
| FundProject: |
| Author Name | Affiliation | E-mail | | Zhao Xipeng | Key Laboratory of Radiological Protection and Nuclear Emergency, China CDC, National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, Beijing 100088, China | | | Yue Baorong | Key Laboratory of Radiological Protection and Nuclear Emergency, China CDC, National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, Beijing 100088, China | | | Xu Hui | Key Laboratory of Radiological Protection and Nuclear Emergency, China CDC, National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, Beijing 100088, China | xuhui@nirp.chinacdc.cn |
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| Abstract:: |
| Objective To determine and optimize the radiation quality of the calibration system for mammography dosimeters in IAEA/WHO Secondary Standard Dosimetry Laboratory and to study the requirements for accuracy of thickness of the aluminum sheets used in the measurement, with a view to ensure the accuracy of the radiation quality. Methods For the measurements of tube voltage and RQR-M radiation quality, a standard kV meter was used to determine the actual tube voltage value of the system under continuous exposure for 30 s by setting tube voltage of 25, 28, 30 and 35 kV, respectively,and aluminum sheet method was used to determine the first half value layer (HVL1). The kV values were adjusted to make the reading of the standard kV meter as close as possible to its nominal value, so as to obtain the set kV value, actual tube voltage and HVL1 per 1 kV within the nominal 25-35 kV range. For effects of different thickness of aluminum sheets on the result of HVL1 measurement, a comparison was made between HVL1 measured by aluminum sheet with thickness of 0.318 mm and 0.369 mm and HVL1 measured under 18 different groups of aluminum sheet using a selected 30 kV tube voltage. Results After the set kV values were adjusted, the actual tube voltage deviations from the nominal values under 25, 28, 30 and 35 kV were reduced from 0.55, 0.34, 0.33, 0.30 to 0.04, 0.02, -0.04, -0.01, and the HVL1 deviations were reduced from 0.011, 0.007, 0.010, 0.012 to 0.000, 0.003, 0.003, 0.010, respectively. When the thickness differences between the two types of aluminum sheet and the reference HVL1 were both within 0.1 mm, the deviations of the measured HVL1 were all less than 0.01 mm Al, and the result was relatively accurate. However, when the differences exceeded that of 0.1 mm, most of the deviations of the measured HVL1 were between 0.01 and 0.02 mm Al, and the measured result was not accurate. Conclusions Although the RQR-M radiation quality of the calibration system was deviated, it is still within the range specified under the IEC 61267-2005. The radiation quality was closer to the standard values after fine-tuning the system tube voltage. In order to measure the HVL1 more accurately, the thickness differences between the used aluminum sheet and nominal HVL1 should not be greater than 0.1 mm Al. |
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