Oxford Brookes University, Faculty of Health and Life Sciences, Oxford OX3 0BP, United Kingdom.
UK Health Security Agency, Radiation, Chemical and Environmental Hazards, Didcot, Oxon, OX11 0RQ, United Kingdom.
J Radiol Prot. 2023 Mar 14;43(1). doi: 10.1088/1361-6498/acbda7.
The consideration of risks from medical diagnostic x-ray examinations and their justification commonly relies on estimates of effective dose, although the quantity is actually a health-detriment-weighted summation of organ/tissue-absorbed doses rather than a measure of risk. In its 2007 Recommendations, the International Commission on Radiological Protection (ICRP) defines effective dose in relation to a nominal value of stochastic detriment following low-level exposure of 5.7 × 10Sv, as an average over both sexes, all ages, and two fixed composite populations (Asian and Euro-American). Effective dose represents the overall (whole-body) dose received by a person from a particular exposure, which can be used for the purposes of radiological protection as set out by ICRP, but it does not provide a measure that is specific to the characteristics of the exposed individual. However, the cancer incidence risk models used by ICRP can be used to provide estimates of risk separately for males and females, as a function of age-at-exposure, and for the two composite populations. Here, these organ/tissue-specific risk models are applied to estimates of organ/tissue-specific absorbed doses from a range of diagnostic procedures to derive lifetime excess cancer incidence risk estimates; the degree of heterogeneity in the distribution of absorbed doses between organs/tissues will depend on the procedure. Depending on the organs/tissues exposed, risks are generally higher in females and notably higher for younger ages-at-exposure. Comparing lifetime cancer incidence risks per Sv effective dose from the different procedures shows that overall risks are higher by about a factor of two to three for the youngest age-at-exposure group, 0-9 yr, than for 30-39 yr adults, and lower by a similar factor for an age-at-exposure of 60-69 yr. Taking into account these differences in risk per Sv, and noting the substantial uncertainties associated with risk estimates, effective dose as currently formulated provides a reasonable basis for assessing the potential risks from medical diagnostic examinations.
在对医疗诊断 X 射线检查的风险进行考虑并为之辩护时，通常依赖于有效剂量的估算，尽管该量实际上是器官/组织吸收剂量的健康损害加权总和，而不是风险的度量。国际放射防护委员会（ICRP）在其 2007 年的建议中，将有效剂量定义为在低水平暴露于 5.7×10Sv 时，随机损害的名义值，这是对所有性别、所有年龄段以及两个固定复合人群（亚洲人和欧洲裔美国人）的平均值。有效剂量代表一个人从特定暴露中接受的总体（全身）剂量，可用于 ICRP 规定的放射防护目的，但它并未提供针对受检个体特征的度量。然而，ICRP 使用的癌症发病率风险模型可用于分别针对男性和女性、按暴露年龄以及针对两个复合人群，提供风险估计。在这里，将这些器官/组织特异性风险模型应用于来自一系列诊断程序的器官/组织特异性吸收剂量估算，以得出终生过量癌症发病率风险估算；器官/组织之间吸收剂量分布的异质性程度将取决于程序。根据暴露的器官/组织，女性的风险通常更高，在暴露年龄较小时尤其如此。比较不同程序的每 Sv 有效剂量的终生癌症发病率风险表明，对于最小暴露年龄组（0-9 岁），整体风险比 30-39 岁成年人高约两倍至三倍，而对于暴露年龄为 60-69 岁的人，则降低了相似的倍数。考虑到每 Sv 风险的差异，并注意到风险估计中存在的大量不确定性，目前形式的有效剂量为评估医疗诊断检查的潜在风险提供了合理的基础。
