Effective doses and risks from medical diagnostic x-ray examinations for male and female patients from childhood to old age

Abstract

Consideration of risks from medical diagnostic X-ray examinations and their justification commonly rely 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 x 10-2 Sv-1, 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 by 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. Changes in the calculation of effective dose to explicitly incorporate sex- and age-specific risks might be considered by ICRP in the future as a way of improving clarity of application in medicine, and more broadly.

The scientific basis for the use of the linear no-threshold (LNT) model at low doses and dose rates in radiological protection

“…It is essential to recall that, in order to construct the nominal risk coefficients and radiological detriment, the ICRP uses and aggregates data relating to persons with diverse characteristics (sex, age, two regions), such that the individual to whom the LNT model is applied is in fact a fictitious subject, averaged between a male and a female, exposed at all ages of their life, and both Asian and American-European (Harrison et al 2023). It is therefore irrelevant to try to demonstrate the accuracy of the LNT model in radiological protection, which remains fundamentally a mathematical construction, which cannot be compared to experimental or epidemiological results, but which integrates them.…”

“…In particular, this aggregated approach is one of the reasons why it is not recommended to use the nominal risk coefficients to perform risk assessments for specific individuals or categories of individuals (Harrison et al 2023). Even more so this statement is applicable to the use of the radiological detriment.…”

“…Clearly, the specificity of individual medical exposures must be considered, and the benefits of diagnostic and therapeutic procedures are recognised, but there is currently no scientific support for the assumption that medical exposures result in a fundamentally different risk from other exposure situations. The application of the LNT model in the medical field therefore seems today as justified in the medical field as in other exposure situations (ICRP 2021a, Harrison et al 2023. Further reflection on the balance between the health benefits of medical applications and risks associated with radiation exposure may be useful (Zanzonico 2016).…”

Towards the establishment of national diagnostic reference levels for chest x-ray examinations in Sri Lanka: a multi-centric study

“…According to the International Commission on Radiological Protection (ICRP) publication 103, the lung, breast, and stomach are identified as the most radiosensitive organs, with the highest tissue weighting factor of 0.12 [5]. Studies have shown that these organs receive high organ doses during the posteroanterior (PA) projection of chest examination [6][7][8]. These concerns underscore the importance of prioritising patient protection during chest x-ray examinations.…”

Losing the balance in risk-benefit analysis

“…Except for the highest age bracket of 75-84 years, where the LACMR value was 0.3 both for males and females, the values for 55-74 years are not lower by orders of magnitude, and thus one cannot ignore risks in this age group. Another recent paper [11] compared lifetime cancer incidence risks per Sv effective dose and showed that overall risks are higher by about a factor of two to three for the youngest age-at-exposure group, 0-9 years, than for 30-39 years adults, and lower by a similar factor for an age-at-exposure of 60-69 years. Thus, considerations of risk-benefits continue to be important even for those in higher ages.…”