Classification of radiation effects for dose limitation purposes: history, current situation and future prospects

Abstract

Radiation exposure causes cancer and non-cancer health effects, each of which differs greatly in the shape of the dose–response curve, latency, persistency, recurrence, curability, fatality and impact on quality of life. In recent decades, for dose limitation purposes, the International Commission on Radiological Protection has divided such diverse effects into tissue reactions (formerly termed non-stochastic and deterministic effects) and stochastic effects. On the one hand, effective dose limits aim to reduce the risks of stochastic effects (cancer/heritable effects) and are based on the detriment-adjusted nominal risk coefficients, assuming a linear-non-threshold dose response and a dose and dose rate effectiveness factor of 2. On the other hand, equivalent dose limits aim to avoid tissue reactions (vision-impairing cataracts and cosmetically unacceptable non-cancer skin changes) and are based on a threshold dose. However, the boundary between these two categories is becoming vague. Thus, we review the changes in radiation effect classification, dose limitation concepts, and the definition of detriment and threshold. Then, the current situation is overviewed focusing on (i) stochastic effects with a threshold, (ii) tissue reactions without a threshold, (iii) target organs/tissues for circulatory disease, (iv) dose levels for limitation of cancer risks vs prevention of non-life-threatening tissue reactions vs prevention of life-threatening tissue reactions, (v) mortality or incidence of thyroid cancer, and (vi) the detriment for tissue reactions. For future discussion, one approach is suggested that classifies radiation effects according to whether effects are life threatening, and radiobiological research needs are also briefly discussed.

The Impact of Circadian Rhythms on Medical Imaging and Radiotherapy Regimes for the Paediatric Patient

“…Preventing cell proliferation protects the lens, but the lens is also the most radiosensitive tissue in the eye (24,25) . It is for this reason that cataract is one of the iconic non-cancer consequences of IR damage (26) . This coupled to the fact that both oxidative defence mechanisms (27) and the repair of X-ray induced double strand breaks (DSBs) in DNA (28) are synchronized by circadian rhythms also means that the timing of radiotherapy and radioimaging procedures needs to be coordinated as we enter personalized medicine.…”

Radiation-Induced Skin Injuries to Patients: What the Interventional Radiologist Needs to Know

“…The first case of human radiogenic dermatitis of the hand was reported in January 1896 [1]. In 1925, several patients suffering from radiation-induced skin injuries were reported by Groedel [2].…”

Radiation and cataract risk: Impact of recent epidemiologic studies on ICRP judgments

“…Early clinical data [4,5] seemed to indicate a high radiation dose threshold for cataracts, though the epidemiologic methodology was weak by present-day standards. Between 1980 and 2011 the International Commission on Radiological Protection (ICRP) recommended a lifetime limitation of dose to the lens of the eye of 2 Sv for acute exposure or 5 Sv for protracted exposure [6,7], with various other limits before that time [8,9]. But in 2012, because of accumulating epidemiologic evidence that lower radiation doses were also associated with lens opacity development, for occupational exposure the ICRP recommended a lifetime equivalent lens dose limit of 0.5 Sv and an annual limit of 20 mSv averaged over five years, with no year exceeding 50 mSv in planned exposure situations [10].…”