Weir A, Schofield K A, McCurrach A
Health Physics, NHS Greater Glasgow and Clyde, West House, 1055 Great Western Road, G12 0XH Glasgow, United Kingdom.
Health Facilities Scotland, NHS National Services Scotland, Gyle Square, 1 South Gyle Crescent, EH12 9EB Edinburgh, United Kingdom.
J Radiol Prot. 2021 Feb 26;41(1). doi: 10.1088/1361-6498/abcf8b.
Optimisation must be carried out on all medical radiological units to ensure doses are as low as reasonably practicable, consistent with the intended purpose. To achieve this, population doses must be estimated and diagnostic reference levels (DRLs) set. For mammography examinations, mean glandular doses (MGDs) are calculated for this purpose. The average MGD per unit is compared to the national mammography DRL, which is applicable to compressed breast thicknesses (CBTs) of 50-60 mm for oblique (OB) views only and set using data from screening units. It is the purpose of this work to assess planar MGDs across Scotland and set DRLs based on data collected from all screening and symptomatic units across Scotland, considering craniocaudal (CC) and OB views and a wider range of CBTs. Data from the most recent dose audit (spanning 20152017) for 67 mammography x-ray units were collated and analysed (26 195 images). No large differences between MGD of CC and OB views were found when considering specific CBT ranges (median difference 2.6%). There was, however, a significant difference between screening and symptomatic data (19%). As expected, MGD increased with CBT and there were significant differences in MGD between manufacturers. From the data analysed, Scottish DRLs were set based on 95th percentile values for digital mammography units for three CBT ranges (30-49, 50-60 and 61-80 mm): 1.3, 1.8 and 2.6 mGy respectively. These values consider OB and CC views collectively. Fifth percentile values are quoted to highlight units at greater risk of insufficient image quality. These MGD values, together with image quality assessments, will facilitate optimisation across Scotland. Results show that use of different CBT ranges and inclusion of CC views increases the number of images included in dose audit data analysis from approximately 12%92%, which is substantially more representative of the population.
必须对所有医学放射单位进行优化，以确保剂量在合理可行的情况下尽可能低，并符合预期目的。为实现这一目标，必须估算人群剂量并设定诊断参考水平（DRL）。对于乳腺钼靶检查，为此要计算平均腺体剂量（MGD）。将每个单位的平均MGD与国家乳腺钼靶DRL进行比较，该DRL仅适用于50 - 60毫米的压缩乳房厚度（CBT）的斜位（OB）视图，并且是使用筛查单位的数据设定的。这项工作的目的是评估苏格兰各地的平面MGD，并根据从苏格兰所有筛查和症状性单位收集的数据设定DRL，同时考虑头尾位（CC）和OB视图以及更广泛的CBT范围。整理并分析了67个乳腺钼靶X射线单位最近一次剂量审核（涵盖2015 - 2017年）的数据（26195张图像）。在考虑特定CBT范围时，未发现CC视图和OB视图的MGD有较大差异（中位数差异为2.6%）。然而，筛查数据和症状性数据之间存在显著差异（19%）。正如预期的那样，MGD随CBT增加，并且不同制造商之间的MGD存在显著差异。根据分析的数据，针对三个CBT范围（30 - 49、50 - 60和61 - 80毫米）的数字乳腺钼靶单位，基于第95百分位数设定了苏格兰DRL：分别为1.3、1.8和2.6毫戈瑞。这些值综合考虑了OB和CC视图。引用第5百分位数是为了突出图像质量不足风险较高的单位。这些MGD值以及图像质量评估将有助于苏格兰各地的优化。结果表明，使用不同的CBT范围并纳入CC视图可使剂量审核数据分析中包含的图像数量从约12%增加到92%，这更能代表总体人群。
