| 赵锡鹏,岳保荣,徐辉.次级标准剂量学实验室乳腺低能X射线剂量仪校准系统线质测定与优化研究[J].中华放射医学与防护杂志,2021,41(10):772-777 |
| 次级标准剂量学实验室乳腺低能X射线剂量仪校准系统线质测定与优化研究 |
| Determination and optimization of radition quality of calibration system for mammography dosimeters in IAEA/WHO secondary standard dosimetry laboratory |
| 投稿时间：2020-12-14 |
| DOI：10.3760/cma.j.issn.0254-5098.2021.10.009 |
| 中文关键词: 乳腺剂量仪校准系统 管电压 第一半值层 铝片厚度 |
| 英文关键词:Calibration system for mammography dosimeters Tube voltage HVL1 Aluminum sheet thickness |
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| 中文摘要: |
| 目的 对国际原子能机构（IAEA）/世界卫生组织（WHO）次级标准剂量学实验室乳腺低能X射线剂量仪校准系统RQR-M线质进行测定和优化，对线质测定中所用铝片厚度精度的要求进行研究，保证低能X射线校准系统线质准确。方法 系统管电压和RQR-M线质测定：分别设定25、28、30和35 kV，连续曝光30 s，使用标准kV计测定系统实际管电压值、使用铝片法测定第一半值层（HVL1）。微调kV设定值，使系统实际管电压值尽可能接近标称值，得到25~35 kV范围内每间隔1 kV的设定值、系统实际管电压值和HVL1；不同厚度铝片对HVL1测定结果的影响：选择30 kV，以[0.318 mm，0.369 mm]厚度铝片测定的HVL1为参考值，与18组不同厚度铝片组合下测量的HVL1进行比较，分析偏差大小。结果 管电压设定值调整后，4个管电压设定值下的系统实际管电压与标称值偏差（kV）由0.55、0.34、0.33和0.30降低为0.04、0.02、-0.04和-0.01。HVL1偏差（mm Al）分别由0.011、0.007、0.010和0.012降低为0.000、0.003、0.003和0.010；HVL1测定中所用两个铝片的厚度与参考HVL1值的偏差均在0.1 mm内时，HVL1测量偏差均在0.01 mm Al以内，测定结果相对准确。但两个铝片的厚度偏差均超过0.1 mm时，HVL1测量值的偏差大部分在0.01~0.02 mm Al，导致测量结果不准确。结论 本校准系统RQR-M线质虽有偏差但在IEC 61267-2005规定范围内，通过微调系统管电压后系统线质更加接近标称值；为更准确地测定乳腺校准系统线质，测量中所用铝片厚度与标称HVL1偏差不宜>0.1 mm Al；对乳腺校准系统线质定期检测以满足国际标准要求是非常重要的。 |
| 英文摘要: |
| 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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