Practical guidance on the assessment of radiation risks for diagnostic radiological examinations

Patient doses cannot be limited; instead, radiological examinations should be justified and optimised to ensure the necessary diagnostic or therapeutic effect with the lowest patient dose achievable. Assessment of the radiation risks from patient exposure is important part of the justification process. Hence, medical staff within the framework of their professional activities should possess necessary information on the data on radiation risk from different types of radiological procedures. An approach has been developed that allows considering age and gender dependences of the risk coefficients of radiogenic cancer and the age and gender distribution of patients for various radiological examinations to assess the individual radiation risk for patient and collective risk for population from medical exposure. The approach is based on a new expanded use of the effective dose concept proposed in ICRP Publication 147 and demonstrated using the medical exposure in the Russian Federation as the example. For 30 radiological examinations that compose about 80% of the collective dose from medical exposure of the public in the Russian Federation radiation risk was assessed based on calculated age and gender specific risk coefficients per unit effective dose. For the rest of the examinations a simplified approach was used to assess the risk, which was based on using an age and gender specific risk coefficient determined for one of 4 anatomical regions (head, neck, chest and abdomen) or for uniform irradiation of the whole body. The proposed approach allows significantly improving the assessment of the radiation risk while continuing to use the effective dose as a dosimetric quantity within the framework of the state program in the Russian Federation. As a result the collective risk from medical examinations in the Russian Federation in 2022 was lower by the factor of 3 compared to the previous assessment based on the effective dose with the nominal risk coefficient.

Awareness and Knowledge of Ionizing Radiation in Common Radiological Investigation and Associated Risks Among Medical and Applied Medical Sciences Students at Majmaah University

AIM

This study aims to evaluate the awareness and knowledge of ionizing radiation in common radiological investigations, as well as the associated risks, among medical and applied medical sciences students at Majmaah University in Majmaah, Saudi Arabia.

MATERIALS AND METHODS

This cross-sectional study involved 209 participants who completed an anonymous electronic questionnaire consisting of 21 questions. Participants were categorized based on demographic characteristics and assessed for their awareness and knowledge of radiation and its associated risks. Data analysis was conducted using the Statistical Package for the Social Sciences (SPSS) software, version 24.0 (IBM Corp., Armonk, NY, USA). Qualitative data comparisons were performed using the Chi-square test, with a p-value of <0.05 considered statistically significant.

RESULTS

A total of 209 participants completed the questionnaire, with a nearly equal distribution of males (49.8%) and females (50.2%). Most of the participants were medical students (59.3%). The overall knowledge score had a mean of 2 (SD=2) and a range of 0-7. The overall awareness score had a mean of 3 (SD=2) and a range of 0-6. Male gender and knowledge had a significant association (p=0.022). Applied medical sciences students had a significantly higher awareness level than medical students (p=0.004). There was a significant association between academic level and knowledge level (p=0.025), which was highest among third-year students.

CONCLUSION

 Overall medical and applied medical sciences students' knowledge and awareness of ionizing radiation dose and the health risks associated with it was reported to be low. The results highlight the need to train medical and applied medical sciences students with sufficient radiological education that enable them to adhere to safe practices in the future.

Patient radiation risk reduction by controlling the tube start angle in single and dual source spiral CT scans: A simulation study

BACKGROUND

Organ doses in spiral CT scans depend on the tube start angle.

PURPOSE

To determine the effective dose in single source CT (SSCT) and dual source CT (DSCT) scans as a function of tube start angle and spiral pitch value to identify the dose reduction potential by selecting the optimal start angle.

METHODS

Using Monte Carlo simulations, dose values for different tube positions with an angular increment of10 ∘ $10^\circ$ and a longitudinal increment of4.5 m m $4.5 \,\mathrm{m}\mathrm{m}$ were simulated over a range of31.5 c m $31.5 \,\mathrm{c}\mathrm{m}$ with collimations of40 mm $40\, \mathrm{mm}$ ,60 mm $60\, \mathrm{mm}$ , and80 m m $80 \,\mathrm{m}\mathrm{m}$ . The simulations were performed for the thorax region of six adult patients based on clinical CT data. From the resulting dose distributions, organ doses and effective dose were determined as a function of tube angle and longitudinal position. Using these per-view dose data, the individual organ doses, as well as the total effective dose, were determined for spiral scans with and without tube current modulation (TCM) with pitch values ranging from 0.5 to 1.5 for SSCT and up to 3.0 for DSCT. The dose of the best and worst tube start angle in terms of dose was determined and compared to the mean dose over all tube start angles.

RESULTS

With increasing pitch and collimation, the dose variations from the effective dose averaged over all start angles increase. While for a collimation of40 m m $40 \,\mathrm{m}\mathrm{m}$ , the variations from the mean dose value stay below5 % $5 \%$ for SSCT, we find that for a spiral scan with a pitch of 3.0 for DSCT with TCM and collimation of80 m m $80 \,\mathrm{m}\mathrm{m}$ , the dose for the best starting angle is on average16 % $16 \%$ lower than the mean value and28 % $28 \%$ lower than the maximum value.

CONCLUSIONS

Variation of the tube start angle in spiral scans exhibits substantial differences in radiation dose especially for high pitch values and for high collimations. Therefore, we suggest to control the tube start angle to minimize patient risk.

Radiation exposure during orthodontic treatment: risk to children and adolescents

OBJECTIVES

To estimate radiation risk to children and adolescents during orthodontic treatment by retrieving number and type of radiographs from the patient records.

MATERIAL AND METHODS

Radiographs, along with justifications for radiation exposure, were obtained retrospectively from the patient records of 1,790 children and adolescents referred to two Swedish orthodontic clinics. Data were grouped according to treatment stage: treatment planning, treatment, and follow-up. Estimated risk was calculated using the concept of effective dose.

RESULTS

Each patient had received around seven radiographs for orthodontic purposes. The most common exposures during treatment planning were one panoramic, one lateral, and three intraoral periapical radiographs. A small number of patients received a tomographic examination (8.2%). Few justifications for treatment planning and follow-up, but more in the actual treatment stage, had been recorded. The most common examinations were to assess root resorption and the positions of unerupted teeth, or simply carry out an unspecified control. The estimated risk of developing fatal cancer was considered low. The radiation risk from orthodontic treatment was equivalent to about 5-10 days of natural background radiation.

CONCLUSIONS

Children and adolescents sometimes undergo multiple radiographic examinations, but despite the low radiation burden, accumulated radiation exposure should be considered and justified in young patients.

NCRP commentary no. 33-recommendations for stratification of equipment use and radiation safety training for fluoroscopy

National Council on Radiation Protection and Measurements Commentary No. 33 'Recommendations for Stratification of Equipment Use and Radiation Safety Training for Fluoroscopy' defines an evidence-based, radiation risk classification for fluoroscopically guided procedures (FGPs), provides radiation-related recommendations for the types of fluoroscopes suitable for each class of procedure, and indicates the extent and content of training that ought to be provided to different categories of facility staff who might enter a room where fluoroscopy is or may be performed. For FGP, radiation risk is defined by the type and likelihood of radiation hazards that could be incurred by a patient undergoing a FGP. The Commentary also defines six training groups of facility staff based on their role in the fluoroscopy room. The training groups are based on a combination of job descriptions and the procedures in which these individuals might be involved. The Commentary recommends the extent and content of training that should be provided to each of these training groups. It also provides recommendations on training formats, training frequency, and methods for demonstrating that the learner has acquired the necessary knowledge.

INFLUENCE OF IONIZING RADIATION ON THE DEVELOPMENT OF BREAST CANCER

Breast cancer (BC) is one of the urgent problems of health care, which is due to a constant trend of growth. One of the risk factors for the development of breast cancer is ionizing radiation (IR). Numerous epidemiological and experimental studies have shown the high sensitivity of the mammary gland (MG) to this factor. Consideration of models of absolute and relative risks of the occurrence of radio-induced tumors of the MG in irradiated persons showed the importance of such factors as age at the time of irradiation, multiplicity. frequency of exposure, dose level and concomitant non-neoplastic diseases of the mammary and thyroid gland (TG). Excess radiation-induced cases of cervical cancer were found among irradiated women after the atomic bombings of Hiroshima and Nagasaki.Epidemiological features of the development of breast cancer under the influence of IV are presented in detail, which is one of the environmental factors involved in the formation of the modern carcinogenic situation. In con-nection with the significant sensitivity of the MG to the carcinogenic effect of IR, this form of neoplasms attracted special attention after the Chornobyl accident. The effect of small doses of radiation after the Chornobyl disaster led to a wave-like change in the incidence of breast cancer in certain periods of the year, and the radiation-induced incidence of this pathology can occur spontaneously.

Paracelsian 'Bergsucht' - lung cancer or radiation-induced fibrosis?

PURPOSE

Assessment of absorbed doses on organs and tissues of miners during radon exposure in the Schneeberg mines in the sixteenth century and calculation of the probability of occurrence of radiation-induced lung cancer and lung fibrosis, considering the life expectancy characteristic and the absence of smoking.

MATERIALS AND METHODS

The expected radon concentration at the Schneeberg mines has been estimated using published data. Modeling of the accumulation of radon in the working tunnels of mine workings was carried out using the RESRAD-Build 4.0, based on the radium concentration in soil and geometric parameters of the mining tunnel from the engravings in Agricola's book. The dynamics of radionuclides in the human body were performed using the WinAct software in accordance with data from ICRP Publications 130 and 137. The values of absorbed doses on the tissues of the respiratory tract were obtained using the IDAC 2.1 program. Several models based on the epidemiology of uranium miners have been used to calculate radiation risks from radon exposure. The probability of male survival at birth and the age-specific frequency of spontaneous lung cancer not associated with radiation for miners of the sixteenth century (nonsmoking men aged 20-40 years) were estimated to properly calculate the radiation risks.

RESULTS

The expected radon concentration in the Schneeberg mines was assessed in the range of 75-100 kBq m-3. The average value of the equilibrium factor was estimated as 0.49 ± 0.03. The annual exposure of miners to radon decay products was assessed as 125-165 WLM year-1. The annual values of absorbed doses to different sections of the respiratory tract were calculated, the maximum absorbed doses of α-radiation are formed on the bronchial and bronchiolar regions of the lungs (2.23 Gy year-1). The deterministic effects as radiation fibrosis of the lungs with 10 years of experience in the mines of Schneeberg have a probability of occurrence from 60 to 100%. All the models used for radiation risk assessments showed that the lifetime risk of developing lung cancer for nonsmoking Schneeberg miners is many times lower than the risk of developing deterministic radiation effects. In contrast, for the smoking cohort of miners in the nineteenth century lung cancer become the dominant cause of death.

CONCLUSIONS

The deterministic radiation effects of Schneeberg miners in sixteenth century, exposed to extremely high levels of radon, such as radiation pneumosclerosis or pulmonary fibrosis, are more likely than the development of radiation-induced lung cancer.

An Assessment of the Public's Perceptions of Radiation Exposure and Risk Associated With Dental Radiographs: A Cross-Sectional Study

BACKGROUND

Ionizing radiation exposure is an ever-present part of the dental diagnostic process. A public concern often exists due to the misunderstanding of the stochastic effects of dental X-rays. This information can be difficult to explain to the patient since many patients are apprehensive about the subject matter.

OBJECTIVE

This article aims to assess the public's knowledge of radiation exposure and estimate the general concern or apprehension about these diagnostic imaging modalities in an effort to understand and therefore ensure patient reassurance during treatment.

METHOD

A questionnaire was conducted asking adults between the ages of 18 to 74 in Jeddah, Saudi Arabia questions pertaining to radiation risk.

RESULTS

 There were 105 respondents; 21.9% showed concerns toward dental imaging, while 20% were skeptical. approximately 74% of respondents believed there was a limit to the amount of radiation exposure a patient could receive for diagnostic purposes, while only eight percent correctly identified that there was no set limit. Only 21.9% knew that a breastfeeding mother could have dental X-rays if need be; 33.3% understood that ionizing radiation from an intra-oral dental X-ray caused less exposure than natural background radiation from a return flight from Jeddah to Dammam.  Conclusions: Patients are not aware of ionizing radiation exposure equivalencies between different imaging modalities. A more effective approach to convey exposure risk would be relating the radiation doses to natural background radiation as comparators.

Personalized Prediction of Patient Radiation Exposure for Therapy of Urolithiasis: An Application and Comparison of Six Machine Learning Algorithms

The prediction of radiation exposure is an important tool for the choice of therapy modality and becomes, as a component of patient-informed consent, increasingly important for both surgeon and patient. The final goal is the implementation of a trained and tested machine learning model in a real-time computer system allowing the surgeon and patient to better assess patient's personal radiation risk. In summary, 995 patients with ureterorenoscopy over a period from May 2016 to December 2019 were included. According to the suggestions based on actual literature evidence, dose area product (DAP) was categorized into 'low doses' ≤ 2.8 Gy·cm² and 'high doses' > 2.8 Gy·cm² for ureterorenoscopy (URS). To forecast the level of radiation exposure during treatment, six different machine learning models were trained, and 10-fold crossvalidated and their model performances evaluated in training and independent test samples. The negative predictive value for low DAP during ureterorenoscopy was 94% (95% CI: 92-96%). Factors influencing the radiation exposure were: age (p = 0.0002), gender (p = 0.011), weight (p < 0.0001), stone size (p < 0.000001), surgeon experience (p = 0.039), number of stones (p = 0.0007), stone density (p = 0.023), use of flexible endoscope (p < 0.0001) and preoperative stone position (p < 0.00001). The machine learning algorithm identified a subgroup of patients of 81% of the total sample, for which highly accurate predictions (94%) were possible allowing the surgeon to assess patient's personal radiation risk. Patients without prediction (19%), the medical expert can make decisions as usual. Next step will be the implementation of the trained model in real-time computer systems for clinical decision processes in daily practice.

The Gap in Insurance Liability for Blood and Research Gamma Irradiators

ABSTRACT

In 2019, a federal contractor accidently breached a 2,900 Ci 137 Cs sealed source while decommissioning it from a University of Washington research building, releasing a single digit curie of its contents. This event contaminated 13 people as well as all seven floors of the research building, which housed the radiation source. Estimates for clean-up costs and lost revenue exceeded $150 million. The magnitude of this cost prompted licensees in possession of such radioactive sources to question whether their insurance coverage is adequate to cover a large-scale incident and if coverage for such exposure even exists. In this article, we identify potential gaps in commercially available insurance policies by evaluating and assessing associated risks, damages, and accountability. While insurance can mitigate the expense associated with remediation, it is unlikely that sufficient limits would exist to fully protect healthcare institutions from direct financial liability in the event that their radioactive sources are implicated in a nuclear, chemical, biological, or radiological (NCBR) (sometimes called CBRN in other literature) mass contamination event. This paper seeks to outline how the risks and liability to healthcare institutions having such gamma irradiators can be reduced significantly by removing them rather than seeking to insure against the cost of remediation in the event of a leak and/or mass contamination. As such, licensees are encouraged to check their policies for the correct coverage and make sure any coverage restriction is removed from their policies. In addition, licensees are also encouraged to explore financial incentives offered by the US government programs to not only dispose of their present gamma irradiator sources at no cost but also to provide financial support to replace them with alternative technologies.

Effective doses for common paediatric diagnostic general radiography examinations at a major Australian paediatric hospital and the communication of associated radiation risks

INTRODUCTION

Health professionals in paediatric medical imaging are routinely required to communicate radiation risks to carers and patients. Effective dose alone cannot be used to specify and communicate the radiation risk for an individual as risks are dependent on many factors including age and patient sex. In this study, we estimated typical effective doses for 20 commonly performed paediatric general radiography examinations using the weight-based imaging protocols employed at a major Australian specialist paediatric hospital. Effective doses were used to estimate and categorise associated age-based stochastic risks with commonly used risk terminology to facilitate communication of risk.

METHODS

Paediatric protocols for common general radiography examinations and World Health Organization 50th percentile weight-for-age data for females and males aged up to 18 years were used to estimate typical effective doses using Monte Carlo software and lifetime risk of cancer incidence using published data. Results were used to determine standardised levels of risk using the Calman risk model.

RESULTS

Effective doses, corresponding lifetime risk of cancer incidence and level of risk category from 20 general radiography examinations for paediatric patients were calculated and presented for ease of communication. Doses ranged from <0.001 mSv (negligible risk) to 1.6 mSv (low risk).

CONCLUSION

Typical effective doses from common paediatric general radiography examinations, the associated lifetime risk of cancer incidence and level of risk have been established for our institution. This can be used to convey risks to health professionals, patients and carers in ways that are easy to understand and compare with other everyday risks.

Radiation Exposure and Lifetime Attributable Risk of Cancer Incidence and Mortality from Low- and Standard-Dose CT Chest: Implications for COVID-19 Pneumonia Subjects

Since the novel coronavirus disease 2019 (COVID-19) outbreak, there has been an unprecedented increase in the acquisition of chest computed tomography (CT) scans. Nearly 616 million people have been infected by COVID-19 worldwide to date, of whom many were subjected to CT scanning. CT exposes the patients to hazardous ionizing radiation, which can damage the genetic material in the cells, leading to stochastic health effects in the form of heritable genetic mutations and increased cancer risk. These probabilistic, long-term carcinogenic effects of radiation can be seen over a lifetime and may sometimes take several decades to manifest. This review briefly describes what is known about the health effects of radiation, the lowest dose for which there exists compelling evidence about increased radiation-induced cancer risk and the evidence regarding this risk at typical CT doses. The lifetime attributable risk (LAR) of cancer from low- and standard-dose chest CT scans performed in COVID-19 subjects is also discussed along with the projected number of future cancers that could be related to chest CT scans performed during the COVID-19 pandemic. The LAR of cancer Incidence from chest CT has also been compared with those from other radiation sources, daily life risks and lifetime baseline risk.

Biophysical Modeling of the Ionizing Radiation Influence on Cells Using the Stochastic (Monte Carlo) and Deterministic (Analytical) Approaches

This review article describes our simplified biophysical model for the response of a group of cells to ionizing radiation. The model, which is a product of 10 years of studies, acts as (a) a comprehensive stochastic approach based on the Monte Carlo simulation with a probability tree and (b) the thereof derived detailed deterministic models describing the selected biophysical and radiobiological phenomena in an analytical manner. Specifically, the presented model describes effects such as the risk of neoplastic transformation of cells relative to the absorbed radiation dose, the dynamics of tumor development, the priming dose effect (also called the Raper-Yonezawa effect) based on the introduced adaptive response approach, and the bystander effect. The model is also modifiable depending on users' potential needs.

Assessment of extremity exposure to technologists working manually with99mTc-labelled radiopharmaceuticals and with an automatic injection system for18F-FDG

The hands of nuclear medicine (NM) personnel involved in radiopharmaceutical preparation and administration can receive significant radiation doses. The dose distribution across the hand is nonuniform and the Hp(0.07) doses obtained by an individual passive ring dosimeter do not always present a real situation. The aim of this study was to assess the extremity exposure of NM workers working with^99mTc-labelled radiopharmaceuticals and with an automatic IRIDE (COMECER, Italy)¹⁸F-FDG injection system. Hp(0.07) doses were measured using calibrated thermoluminescent dosimeters-100 (TLD-100) and were read by a RIALTO TLD (NE Technology) reader. It was found that the most exposed parts of the hand during work with¹⁸F and^99mTc radionuclides are the fingertips of the thumb, index finger and middle finger. The maximum fingertip doses were 1.3-2.4 times higher compared with the doses from the typical monitoring position (base of the middle finger of the dominant hand). When working with^99mTc, the average hand doses were relatively high, i.e. 0.17 ± 0.04 and 0.37 ± 0.13 mSv Gbq^-1for the left and the right hand, respectively, during preparation, and 58 ± 20 and 53 ± 13µSv GBq^-1for the left and the right hand, respectively, during administration of^99mTc labelled radiopharmaceuticals. Meanwhile, the lowest doses were found for hands during administration of¹⁸F-FDG (average hand dose 28 ± 13µSv GBq^-1for the left hand and 28 ± 7µSv GBq^-1for the right hand), which shows the advantages of automated injection/infusion systems, thus implementation of automatic infusion/injection in hospitals could be an expedient way to optimize Hp(0.07) doses to NM workers.

Diagnostic Imaging of Pregnant Women and Fetuses: Literature Review

Healthcare providers have acknowledged the dangers of radiation exposure to embryonic and fetal health, yet diagnostic imaging of pregnant women is increasing. Literature that pertains to the topic of interest was reviewed to collect tertiary data. The purpose of this literature review was to present the various radiation risks for pregnant women and the fetus depending on the gestational age of the pregnancy. The specific effects of radiation on pregnant women and the fetus, X-ray risks depending on the gestational age of the pregnancy, and other potential health effects when performing diagnostic imaging procedures on pregnant women were discussed in this review. In addition, ethical issues have been considered by improving overall communication to minimize unnecessary radiation exposure to pregnant women and fetuses.

Patient-specific radiation risk-based tube current modulation for diagnostic CT

PURPOSE

Modern CT scanners use automatic exposure control (AEC) techniques, such as tube current modulation (TCM), to reduce dose delivered to patients while maintaining image quality. In contrast to conventional approaches that minimize the tube current time product of the CT scan, referred to as mAsTCM in the following, we herein propose a new method referred to as riskTCM which aims at reducing the radiation risk to the patient by taking into account the specific radiation risk of every dose-sensitive organ.

METHODS

For current mAsTCM implementations, the mAs-product is used as a surrogate for the patient dose. Thus they do not take into account the varying dose sensitivity of different organs. Our riskTCM framework assumes that a coarse CT reconstruction, an organ segmentation and an estimation of the dose distribution can be provided in real time, e.g. by applying machine learning techniques. Using this information riskTCM determines a tube current curve that minimizes a patient risk measure, e.g. the effective dose, while keeping the image quality constant. We retrospectively applied riskTCM to 20 patients covering all relevant anatomical regions and tube voltages from 70 kV to 150 kV. The potential reduction of effective dose at same image noise is evaluated as a figure of merit and compared to mAsTCM and to a situation with a constant tube current referred to as noTCM.

RESULTS

Anatomical regions like the neck, thorax, abdomen and the pelvis benefit from the proposed riskTCM. On average, a reduction of effective dose of about 23 % for the thorax, 31 % for the abdomen, 24 % for the pelvis, and 27% for the neck have been evaluated compared to today's state-of-the-art mAsTCM. For the head, the resulting reduction of effective dose is lower, about 13 % on average compared to mAsTCM.

CONCLUSIONS

With a risk-minimizing tube current modulation, significant higher reduction of effective dose compared to mAs-minimizing tube current modulation is possible. This article is protected by copyright. All rights reserved.

What's better for our health? Conducting protective actions during a nuclear emergency or accepting a certain radiation dose?

The threat caused by ionising radiation has resulted in the establishment of strict radiation protection guidelines. This is especially true for severe nuclear power plant (NPP) accident scenarios, which may involve the release of significant amounts of ionising radiation. However, we believe that the fine balance between the benefit of a certain protective action (e.g. evacuation) and its risks is not always accounted for properly. Deaths and mental health problems have been associated with protective actions (e.g. evacuation) implemented in the response to the Fukushima Daiichi (NPP) accident in 2011. The protective actions were implemented consistent with international recommendations, to reduce radiation-induced health effects, even though the off-site effective doses were too low to indicate that there would be any discernible radiation-induced health effects. In this paper, we will provide a first step for the development of tools to evaluate the risk of protective actions versus the radiation-induced health risk. Over 50 papers were selected as useful from more than 600 reviewed papers to characterise the health impact of protective actions taken during different emergencies (including, technical and natural emergencies). An analysis was performed comparing the radiation-induced health effects averted by protective actions with the health effects associated with the protective actions. We concentrated our analysis on deaths and mental health problems associated with protective actions compared with the inferred radiation-induced deaths averted by the protective actions. Our analysis is stated in terms of absolute risk (cases per 1000) of health effects to allow for a direct comparison. It indicates that taking protective actions consistent with dose criteria typically used in many countries could result in more excess deaths than the inferred radiation-induced deaths prevented, as well as resulting in mental health problems. We identified that residents of facilities for long stays and the elderly are particularly vulnerable and a significant number of the deaths among the general public are associated with a lack of emergency preparedness provisions.

At Which Mean Glandular Dose Does the Benefit of Breast Cancer Deaths Averted Equal the Risk of Lives Lost to Screening From Radiation-induced Malignancy for Mammography With and Without Tomosynthesis?

OBJECTIVE

To estimate benefit-to-radiation-risk mean glandular dose (MGD) equivalence values for screening mammography, defined as the yearly MGD (over a 10-year period) at which the estimated benefit of mammography in terms of deaths averted equals the estimated risk of lives lost to screening due to radiation exposure (a benefit-to-risk ratio of 1).

METHODS

Benefit-to-risk ratios were calculated as the ratio of breast cancer deaths averted and lives lost to screening over 10-year intervals starting at age 40 for mammography and tomosynthesis using previously published methodology. The MGD values at which estimated benefit equals risk were tabulated.

RESULTS

The MGD values at which benefit-to-risk equivalence points were met for digital screening mammography are 63 milligray (mGy) (ages 40-49), 88 mGy (ages 50-59), 176 mGy (ages 60-69), and 336 mGy (ages 70-79). The MGD values that met benefit-to-risk equivalence for screening tomosynthesis plus digital mammography or synthetic mammography are 80 mGy (ages 40-49), 111 mGy (ages 50-59), 224 mGy (ages 60-69), and 427 mGy (ages 70-79).

CONCLUSION

Cutoff MGD values at which the estimated benefit from screening equals the estimated risk are well above standard screening MGD exposures. Care is necessary to ensure that threshold values are not exceeded during a screening exam, particularly for women ages 40-49 years old when using digital mammography plus tomosynthesis (due to an approximate doubling of dose per exam that will more readily exceed cutoff MGD values) and when many additional views are obtained.

Outdoor Radon as a Tool to Estimate Radon Priority Areas-A Literature Overview

Doses from the exposure to outdoor radon are typically an order of magnitude smaller than those from indoor radon, causing a greater interest on investigation of the latter for radiation protection issues. As a consequence, assessment of radon priority areas (RPA) is mainly based on indoor radon measurements. Outdoor radon measurements might be needed to guarantee a complete estimation of radiological risk and may help to improve the estimation of RPA. Therefore, authors have analysed the available literature on outdoor radon to give an overview of outdoor radon surveys and potential correlation with indoor radon and estimation of RPA. The review has shown that outdoor radon surveys were performed at much smaller scale compared to indoor radon. Only a few outdoor radon maps were produced, with a much smaller density, covering a larger area, and therefore putting doubt on the representativeness of this data. Due to a large variety of techniques used for outdoor radon measurements and requirement to have detectors with a high sensitivity and resistance to harsh environmental conditions, a standardised measurement protocol should be derived. This is no simple endeavour since there are more applications in different scientific disciplines for outdoor radon measurements compared to indoor radon.

Review of engagement activities to promote awareness of radiation and its associated risk amongst the Japanese public before and after the Fukushima Daiichi Nuclear Power Plant accident

Following the Fukushima Daiichi Nuclear Power Plant accident in 2011, many radiation experts directly experienced a vast gap between ideal and real public understanding (PU) of radiation in risk communication. Therefore, this study collated and reviewed information about PU activities for radiation and its risk that six Japanese academic societies-which seem to be socially neutral expert communities-related to radiation and radiation risk conducted before and after the accident. Activities these radiation-related societies provided to the general public were discussed from the following perspectives: (a) difficulties in two-way communication due to resources, motivation and public interest and concerns; (b) balance between academic research and PU activities; (c) academic societies' building trust with the public while ensuring member experts' neutrality and independence; and (d) discussions among academic societies to prepare for public engagement. We hope that this paper encourages experts and academic societies in radiation protection to hold more national and international discussions about their roles in public communication and outreach.

IRPA practical guidance for engagement with the public on radiation and risk

The International Radiation Protection Association, IRPA, promotes the worldwide enhancement of professional competence, radiation protection (RP) culture and practice by providing benchmarks of good practice, as well as encouraging the application of the highest standards of professional conduct, skills and knowledge for the benefit of individuals and society. Enhancing public understanding of radiation and risk is highlighted by experiences from past emergencies, including the accident at Tokyo Electric Power Company's (TEPCO) Fukushima Daiichi Nuclear Power Plant in 2011 and the following post-disaster recovery, as one of the most important challenges, and this challenge is common across almost all public interfaces regarding radiation and risk. To this end IRPA has been continuing a Task Group activity for Public Understanding since 2013. After a series of workshops in various regions of the world, the IRPA draft guidance was developed and issued for consultation of the Associate Societies in 2019. Through these processes, IRPA received a lot of helpful comments and suggestions. IRPA finally published 'Practical Guidance for Engagement with the Public on Radiation and Risk' on the IRPA website in October 2020. The objective of the guidance is two-fold. Firstly, it is to enthuse all of us in our profession to become more active public advocates for RP. Secondly, it is to provide information, experiences and techniques to help us to become more effective and comfortable in this challenging task. This paper provides a key summary of the published IRPA guidance.

Referring physician perspective on how to handle frequent use of CT imaging

The increasing use of computed tomography (CT) and other relatively high radiation dose exams in a recurrent manner result in radiation risks to individual patients. Recent studies have provided alarming information not only to the radiological community but also to referring physicians. We, as referring physicians, are often implicated in the overuse of imaging. However, a recent paper rightfully summarized the situation that despite the best use of available clinical decision support system for prescribing an imaging exam at a major hospital in the USA, many patients were found to have high cumulative doses. Motivated by the cue provided by the paper in this very journal, we decided to come forward with a possible solution taking the example of the drug prescription system that we routinely use. We provide a template to translate prescription drug monitoring program to ionising radiation imaging. We suggest that all body CT exams should be monitored at an individual, prescriber, and institution level for frequency of use. Furthermore, there should be radiation risk stratification of an individual patient based on the cumulative radiation burden in recent years. Further, an individual's radiation risk-stratified in different risk levels should be available for use by the referring/ordering clinicians at the point of care. Finally, we feel distanced by the use of multiple scary radiation dose quantities in different imaging modalities and would prefer as simple a metric as 'milligram.'

[Risk Communication of Radiation Exposure for Diagnosis: A Questionnaire Survey]

PURPOSE

We investigated how a radiologic technologist explains to a patient about the risk of radiation exposure involved by the radiological examination.

METHODS

In this institutional review board-approved, cross-sectional study, an online questionnaire link was emailed to 650 radiological technologists who are members of the National Hospital Kanto Koshinetsu Radiological Technologist Association. The questions to survey risk communication included the ideal and reality explanation for radiation exposure to patients, the respondent's educational background, and years of experience. Statistical analysis was performed using the Kruskal-Wallis test and Bonferroni correction as a multiple comparison test.

RESULTS

Among the 650 radiological technologists, 245 (37.7%) completed the online questionnaire. The most common response was to compare and convey the doses of radiation during examination and background radiation when asked by a patient about risk. In the cross-analysis, the Kruskal-Wallis test showed no significant difference in what was explained according to educational background. According to years of experience, a significant difference in the content was found about explanation of the risk to patients.

CONCLUSIONS

We clarified the actual condition of risk communication related to the exposure in radiological examinations. In the future, development of risk communication is expected by improving the knowledge and information of "risk" and giving explanations requested by patients.

Health effects triggered by tritium: how do we get public understanding based on scientifically supported evidence?

The Commission for 'Corresponding to Radiation Disaster of the Japanese Radiation Research Society' formulated a description of potential health effects triggered by tritium. This was in response to the issue of discharging water containing tritium filtered by the Advanced Liquid Processing System (ALPS), generated and stored in Fukushima Daiichi Nuclear Power Station after the accident. In this review article, the contents of the description, originally provided in Japanese, which gives clear and detailed explanation about potential health effects triggered by tritium based on reliable scientific evidence in an understandable way for the public, were summarized. Then, additional information about biochemical or environmental behavior of organically bound tritium (OBT) were summarized in order to help scientists who communicate with general public.

Radiological Risk to Human and Non-Human Biota Due to Radioactivity in Coastal Sand and Marine Sediments, Gulf of Oman

Natural and 137Cs radioactivity in coastal marine sediment samples was measured using gamma spectrometry. Samples were collected at 16 locations from four beaches along the coastal area of Muscat City, Gulf of Oman. Radioactivity in beach sand was used to estimate the radiological risk parameters to humans, whereas the radioactivity in marine sediments was used to assess the radiological risk parameters to non-human biota, using the ERICA Tool. The average radioactivity concentrations (Bqkg-1) of 226Ra, 232Th, 40K, 210Pb and 137Cs in sediments (sand) were as follows: 16.2 (16.3), 34.5(27.8), 54.7 (45.6), 46.8 (44.9) and 0.08 (0.10), respectively. In sand samples, the estimated average indoor (Din) and outdoor (Dout) air absorbed dose rates due to natural radioactivity were 49.26 and 27.4 and the total effective dose (AEDTotal; µSvy-1) ranged from 150.2 to 498.9 (average: 275.2). The measured radioactivity resulted in an excess lifetime cancer risk (ELCR) in the range of 58-203 (average: 111) in and an average gonadal dose (AGD; µGy.y-1) ranged from 97.3 to 329.5 (average: 181.1). Total dose rate per marine organism ranged from 0.035 µGy h-1 (in zooplankton) to 0.564 µGy h-1 (in phytoplankton). The results showed marine sediments as an important source of radiation exposure to biota in the aquatic environment. Regular monitoring of radioactivity levels is vital for radiation risk confinement. The results provide an important radiological risk profile parameter to which future radioactivity levels in marine environments can be compared.