Determination of average glandular dose with modern mammography units for two large groups of patients
Determination of average glandular dose with modern mammography units for two large groups of patients
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DOI：
10.1088/0031-9155/42/4/004
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发表时间：
1997-04-01
影响因子：
3.5
通讯作者：
Zoetelief, J
中科院分区：
文献类型：
--
作者：
Klein, R;Aichinger, H;Zoetelief, J
直到最近，钼阳极-钼滤镜x射线管组件几乎完全用于乳房x光检查。现代乳房x线摄影装置提供了采用各种阳极过滤器组合的可能性，目的是使x射线光谱适应压缩乳房的厚度和成分。本报告提供了用现代x射线设备进行乳房x光检查的两大组病人（其中一组为1678名妇女，另一组为945名妇女）的辐射照射资料，以及评价所需的剂量学资料。为了剂量学的目的，光谱信息是必不可少的。x射线光谱已经确定了各种阳极过滤器组合从测量与锗探测器。根据这些光谱，计算了不同阳极过滤器组合、压缩乳房厚度从2到9厘米以及乳腺成分从0到100%不等的情况下，从空气中无kerma到平均腺体剂量的转换因子（fi因子）。在实际乳房x线摄影过程中测定各种数量，包括入口表面空气度（ESAK）、管输出量、管负载（TL）、腺组织比例（FGL）和压缩乳房厚度。平均腺剂量（AGD）是通过校正组织成分的g因子以及标准乳腺成分的g值来确定的，即按质量计算脂肪组织占50%，腺组织占50%。结果表明，平均而言，实际乳房成分的影响会导致约15%的变化。对于组1和组2，平均腺体剂量的平均值（使用组织组成校正的g因子）分别为1.59和2.07 mGy。每位女性的平均接触次数分别为3.4次和3.6次。乳房压缩厚度平均值分别为55.9 mm和50.8 mm。组1平均年龄53.6岁（组2无年龄记录）。腺体组织FGL的质量分数随压缩乳房厚度和患者年龄的增加而降低（从25 mm时的75%到80 mm时的20%，从20岁时的65%到75岁时的30%）。对于中等大小的乳房，即压缩乳房厚度为55mm， FGL约为35%，这表明标准混合物（FGL = 50%）可能需要进行一些修改，特别是因为另一项研究中有类似结果的额外证据。
Until recently, for mammography Mo anode-Mo filter x-ray tube assemblies were almost exclusively used. Modem mammography units provide the possibility to employ a variety of anode-filter combinations with the aim of adapting the x-ray spectrum to compressed breast thickness and composition. The present contribution provides information on the radiation exposure of two large groups of patients (one of 1678 and one of 945 women) who were mammographed with modern x-ray equipment, and on the dosimetry necessary for the evaluation.For dosimetric purposes spectral information is essential. X-ray spectra have been determined for various anode-filter combinations from measurements with a Ge detector. Based on these spectra, conversion factors from air kerma free in air to average glandular dose (fi factors) have been calculated for different anode-filter combinations, compressed breast thickness ranging from 2 to 9 cm and breast compositions varying from 0 to 100% glandular tissue. Determinations of various quantities, including entrance surface air kerma (ESAK), tube output, tube loading (TL), fraction of glandular tissue (FGL) and compressed breast thickness, were made during actual mammography. Average glandular dose (AGD) was determined using g factors corrected for tissue composition as well as g values for standard breast composition, i.e. 50% adipose tissue and 50% glandular tissue by mass. It is shown that, on average, the influence of the actual breast composition causes variations of the order of about 15%.For group 1 and group 2, the mean values of average glandular dose (using g factors corrected for tissue composition) were 1.59 and 2.07 mGy respectively. The number of exposures per woman was on average 3.4 and 3.6 respectively. The mean value of compressed breast thickness was 55.9 and 50.8 mm respectively. The mean age of group 1 was 53.6 years (for group 2 the age was not recorded).The fraction by mass of glandular tissue FGL decreases with increasing compressed breast thickness and age of patient (from 75% at 25 mm to 20% at 80 mm, and from 65% at 20 years to 30% at 75 years). For a medium-sized breast, i.e. a compressed breast thickness of 55 mm, FGL is about 35%, indicating that the standard mix (FGL = 50%) might need some modification, particularly because of additional evidence from another investigation with similar results on FGL.