Towards quantitative justification

Dr John Kotre, Visiting Research Fellow at the University of Cumbria, UK, won the BIR/GE Radiation Safety Travel award 2023 for his application based on The J-factor: towards quantitative justification for medical radiation exposure

Radiation protection: from martyrs to ‘zero dose’: changes to protection and zero dose techniques such as robotics, optical image guidance

John Kotre presents on the subject of radiation exposure to radiology staff. He concludes: radiation protection for radiology staff has come a long way in 120 years and doses are well controlled by standard procedures; significant investment aimed solely at further reducing staff doses could be argued not to be within the ALARP principle; the most valuable technical developments would seem be those aimed at reductions in patient radiation doses which in turn offer the possibility of reduced staff doses

Duty of Candour and Clinically Significant Accidental or Unintended Exposures: revisiting the definition of moderate harm for patient safety incidents involving ionising radiation

Objective: To explore a quantitative interpretation of the term ‘moderate harm’ as applied to the triggering of the Duty of Candour associated with Clinically Significant Accidental and Unintended Exposures of ionising radiation. Methods: Current definitions of ‘moderate harm’ were matched to the lay descriptions of disease and injury states used in the calculation of detriment as disability-adjusted life years (DALY) by the World Health Organisation, to obtain a value of detriment associated with ‘moderate harm’. Published conversion factors between effective dose and DALY were used to calculate the effective dose associated with the same detriment. Results: The DALY loss associated with a moderate harm incident is estimated as 0.0216 years. This corresponds to the detriment resulting from an exposure to ionising radiation of 21 mSv. An effective dose of 21 mSv relates to a probability of induced cancer of 0.0012. Conclusion: The results obtained closely match existing guidance although the method used is completely different. It is concluded that there is no evidence to change the existing guidance on the triggering of DoC in radiation incidents. Advances in knowledge: An alternative approach to linking ‘moderate harm’ and radiation detriment has reinforced existing guidance

Increasing the public awareness of justification

One of the requirements of the UK Ionising Radiation (Medical Exposure) Regulations 2017 is that all medical exposures must be justified, in that the benefit must have been determined to exceed the risk before the exposure can proceed. The field of medical exposure to ionising radiation is in the rare position of having this explicit legal requirement. In this article it is argued that, although separate information on benefit and risk is also required for implied or express informed consent prior to exposure, justification happens independently of this, is simple to explain, and is easily related to the commonly understood basis of medical ethics. It seems reasonable, therefore, to make patients and the public aware of the protection that UK law already provides for them. A proposal for a single-sentence general statement on justification is made

Comparing benefit and detriment from medical diagnostic radiation exposure using disability-adjusted life years: towards quantitative justification

Justification of medical radiation exposure is one of the main elements of radiation protection for patients. For a medical exposure to proceed, the benefit from the procedure must have been determined to be greater than the detriment. It is rare, however, that justification can be stated quantitatively as a ratio of benefit to detriment, or as a net benefit, and this is particularly true for medical diagnostic exposures associated with non-fatal diseases where survival statistics do not apply. The concept of the disability-adjusted life year (DALY) is well established as a measure of disease severity in public health, and there have been calls to revise the international system of radiation protection dosimetry to employ the DALY as a measure of radiation detriment. This paper looks at possible routes to quantify the benefit and detriment aspects of justification based on initial published results for the use of the DALY as a measure of radiation detriment, together with established values of DALY for a range of diseases. Although spreadsheet-style solutions for the calculation of a justification factor based on statistical life tables can be devised, these will be shown to have some limitations. A justification factor based on the rate of change of benefit divided by the rate of change of detriment following medical exposure is proposed. This factor is simple to calculate, is age independent, can apply to non-fatal diseases and is argued to have logical and ethical advantages for the explanation of the relative benefits and detriments of radiological procedures to patients

ALARP: when does reasonably practicable become rather pricey?

The Ionising Radiations Regulations 2017 require employers to restrict radiation doses to their employees and the public to be As Low As Reasonably Practicable. This article looks at the boundary between what might be considered to be reasonable and unreasonable in protecting staff and the general public in the field of hospital-based diagnostic radiology. A simple test for locating this boundary based on a cost-benefit approach is devised and its use illustrated using hospital-based radiation protection examples. It is concluded that a cost-benefit calculation based on the legal definition of As Low As Reasonably Practicable may have some use in the support of radiation protection decision-making in the hospital environment, but only within the context of existing legal, practical and ethical considerations

Application of ALARP cost-benefit analysis to hospital-based radiation protection

The UK Ionising Radiations Regulations 2017 require employers to restrict radiation doses to their employees and the public to be As Low As Reasonably Practicable (ALARP). This article looks at the boundary between what might be considered to be reasonable and unreasonable in protecting staff and the general public in the field of hospital-based diagnostic radiology. Guidance on cost-benefit analysis in support of ALARP has been used to formulate relationships for the estimation of the cost at which a radiation protection intervention is no longer ALARP. These relationships allow for a direct link between a reduction in radiation exposure and the maximum ALARP cost of intervention. Application of the approach to hospital-based radiation protection situations show that the ALARP cost limits for protecting radiation workers against the residual risks in the hospital environment are relatively low. Conversely, the ALARP limit to investment in public dose reduction by means of reducing patient doses can be very high

No strong evidence for increased risk of breast cancer 8-26 years after multiple mammograms in their 30s in females at moderate and high familial risk

OBJECTIVE: To assess the risks of induction of breast tumours from frequent screening mammography in younger females. METHODS: A study group of 853 females was identified who had at least 5 mammograms starting before 37 years of age, with 4 or more before the age of 40 years. These were followed up from their 40th birthday or 8 years from their first mammogram, and their cancer incidence was compared with that of a control group of 1103 females who had an average of 5 mammograms between the ages of 40 and 46 years. All females in the study were previously assessed to be at moderate familial risk or higher. RESULTS: There were 43 incident breast cancers in the study group after the 8-year start point, whereas 38.3 were expected from life-table calculations (RR 1.12; 95% CI: 0.83 to 1.51). In the control group, 50 incident breast cancers developed some time after their first mammogram in follow up to age 60 years. The observed, expected ratio from life tables in this group was 0.94 (95% CI: 0.71–1.24), similar to that in the study group. CONCLUSION: There was no trend to greater cancer incidence in those receiving mammograms earlier. ADVANCES IN KNOWLEDGE: This study shows that there is no substantial effect on the induction of additional primary breast tumours from frequent mammography starting at <37 years of age. Further work on larger numbers of females is necessary to assess longer term risks and determine whether a small excess cancer effect may be present