COPD Imaging on a 3rd Generation Dual-Source CT: Acquisition of Paired Inspiratory-Expiratory Chest Scans at an Overall Reduced Radiation Risk

As stated by the Fleischner Society, an additional computed tomography (CT) scan in expiration is beneficial in patients with chronic obstructive pulmonary disease (COPD). It was thus the aim of this study to evaluate the radiation risk of a state-of-the-art paired inspiratory-expiratory chest scan compared to inspiration-only examinations. Radiation doses to 28 organs were determined for 824 COPD patients undergoing routine chest examinations at three different CT systems-a conventional multi-slice CT (MSCT), a 2nd generation (2nd-DSCT), and 3rd generation dual-source CT (3rd-DSCT). Patients examined at the 3rd-DSCT received a paired inspiratory-expiratory scan. Organ doses, effective doses, and lifetime attributable cancer risks (LAR) were calculated. All organ and effective doses were significantly lower for the paired inspiratory-expiratory protocol (effective doses: 4.3 ± 1.5 mSv (MSCT), 3.0 ± 1.2 mSv (2nd-DSCT), and 2.0 ± 0.8 mSv (3rd-DSCT)). Accordingly, LAR was lowest for the paired protocol with an estimate of 0.025 % and 0.013% for female and male patients (50 years) respectively. Image quality was not compromised. Paired inspiratory-expiratory scans can be acquired on 3rd-DSCT systems at substantially lower dose and risk levels when compared to inspiration-only scans at conventional CT systems, offering promising prospects for improved COPD diagnosis.

A comparison of COVID-19 and imaging radiation risk in clinical patient populations

The outbreak of coronavirus SARS-COV2 affected more than 180 countries necessitating fast and accurate diagnostic tools. Reverse transcriptase polymerase chain reaction (RT-PCR) has been identified as a gold standard test with Chest CT and Chest Radiography showing promising results as well. However, radiological solutions have not been used extensively for the diagnosis of COVID-19 disease, partly due to radiation risk. This study aimed to provide quantitative comparison of imaging radiation risk versus COVID risk. The analysis was performed in terms of mortality rate per age group. COVID-19 mortality was extracted from epidemiological data across 299,  004 patients published by ISS-Integrated surveillance of COVID-19 in Italy. For radiological risk, the study considered 659 Chest CT performed in adult patients. Organ doses were estimated using a Monte Carlo method and then used to calculate Risk Index that was converted into an upper bound for related mortality rate following NCI-SEER data. COVID-19 mortality showed a rapid rise for ages >30 years old (min: 0.30%; max: 30.20%), whereas only four deaths were reported in the analysed patient cohort for ages <20 years old. The rates decreased for radiation risk across age groups. The median mortality rate across all ages for Chest-CT and Chest-Radiography were 0.007% (min: 0.005%; max: 0.011%) and 0.0003% (min: 0.0002%; max: 0.0004%), respectively. COVID-19, Chest Radiography, and Chest CT mortality rates showed different magnitudes and trends across age groups. In higher ages, the risk of COVID-19 far outweighs that of radiological exams. Based on risk comparison alone, Chest Radiography and CT for COVID-19 care is justified for patients older than 20 and 30 years old, respectively. Notwithstanding other aspects of diagnosis, the present results capture a component of risk consideration associated with the use of imaging for COVID. Once integrated with other diagnostic factors, they may help inform better management of the pandemic.

A New Era in Zero X-ray Ablation

In this article, the authors focus on the importance of the zero X-ray ablation approach in electrophysiology. Radiation exposure related to conventional transcatheter ablation carries small but non-negligible stochastic and deterministic effects on health. Non-fluoroscopic mapping systems can significantly reduce, or even completely avoid, radiological exposure. The zero X-ray approach determines potential clinical benefits in terms of reduction of ionising radiation exposure, as well as safe technical advantages. The use of this method can result in similar outcomes when compared to the conventional fluoroscopic technique. These results are achieved without altering the duration, or compromising the effectiveness and safety, of the procedure. The zero X-ray ablation approach is a feasible and safe alternative to fluoroscopy, which is often only used in selected cases for troubleshooting. The non-fluoroscopic approach is considered a milestone for cancer prevention in ablation procedures.

Projected Cancer Risks to Residents of New Mexico from Exposure to Trinity Radioactive Fallout

The Trinity nuclear test, conducted in 1945, exposed residents of New Mexico to varying degrees of radioactive fallout. Companion papers in this issue have detailed the results of a dose reconstruction that has estimated tissue-specific radiation absorbed doses to residents of New Mexico from internal and external exposure to radioactive fallout in the first year following the Trinity test when more than 90% of the lifetime dose was received. Estimated radiation doses depended on geographic location, race/ethnicity, and age at the time of the test. Here, these doses were applied to sex- and organ-specific risk coefficients (without applying a dose and dose rate effectiveness factor to extrapolate from a population with high-dose/high-dose rates to those with low-dose/low-dose rates) and combined with baseline cancer rates and published life tables to estimate and project the range of radiation-related excess cancers among 581,489 potentially exposed residents of New Mexico. The total lifetime baseline number of all solid cancers [excluding thyroid and non-melanoma skin cancer (NMSC)] was estimated to be 183,000 from 1945 to 2034. Estimates of ranges of numbers of radiation-related excess cancers and corresponding attributable fractions from 1945 to 2034 incorporate various sources of uncertainty. We estimated 90% uncertainty intervals (UIs) of excess cancer cases to be 210 to 460 for all solid cancers (except thyroid cancer and NMSC), 80 to 530 for thyroid cancer, and up to 10 for leukemia (except chronic lymphocytic leukemia), with corresponding attributable fractions ranging from 0.12% to 0.25%, 3.6% to 20%, and 0.02% to 0.31%, respectively. In the counties of Guadalupe, Lincoln, San Miguel, Socorro, and Torrance, which received the greatest fallout deposition, the 90% UI for the projected fraction of thyroid cancers attributable to radioactive fallout from the Trinity test was estimated to be from 17% to 58%. Attributable fractions for cancer types varied by race/ethnicity, but 90% UIs overlapped for all race/ethnicity groups for each cancer grouping. Thus, most cancers that have occurred or will occur among persons exposed to Trinity fallout are likely to be cancers unrelated to exposures from the Trinity nuclear test. While these ranges are based on the most detailed dose reconstruction to date and rely largely on methods previously established through scientific committee agreement, challenges inherent in the dose estimation, and assumptions relied upon both in the risk projection and incorporation of uncertainty are important limitations in quantifying the range of radiation-related excess cancer risk.

Biologically-based modeling of radiation risk and biomarker prevalence for papillary thyroid cancer in Japanese a-bomb survivors 1958-2005

PURPOSE

Thyroid cancer of papillary histology (PTC) is the dominant type in radio-epidemiological cohorts established after nuclear accidents or warfare. Studies on post-Chernobyl PTC and on thyroid cancer in the life span study (LSS) of Japanese a-bomb survivors consistently revealed high radiation risk after exposure during childhood and adolescence. For post-Chernobyl risk assessment overexpression of the CLIP2 gene was proposed as molecular biomarker to separate radiogenic from sporadic PTC. Based on such binary marker a biologically-based risk model of PTC carcinogenesis has been developed for observational Chernobyl data. The model featured two independent molecular pathways of disease development, of which one was associated with radiation exposure. To gain credibility the concept for a mechanistic risk model must be based on general biological features which transcend findings in a single cohort. The purpose of the present study is therefore to demonstrate portability of the model concept by application to PTC incidence data in the LSS. By exploiting the molecular two-path concept we improve the determination of the probability of radiation causing cancer (POC).

MATERIALS AND METHODS

The current analysis uses thyroid cancer incidence data of the LSS with thyroid cancer diagnoses and papillary histology (n = 292) from the follow-up period between 1958 and 2005. Risk analysis was performed with both descriptive and biologically-based models.

RESULTS

Judged by goodness-of-fit all applied models described the data almost equally well. They yielded similar risk estimates in cohorts post-Chernobyl and LSS. The preferred mechanistic model was selected by biological plausibility. It reflected important features of an imperfect radiation marker which are not easily addressed by descriptive models. Precise model predictions of marker prevalence in strata of epidemiological covariables can be tested by molecular measurements. Application of the radiation-related molecular pathway from our preferred model in retrospective risk assessment decreases the threshold dose for 50% POC from 0.33 (95% confidence interval (CI) 0.18; 0.64) Gy to 0.04 (95% CI 0.01; 0.19) Gy for females and from 0.43 (95% CI 0.17; 1.84) Gy to 0.19 (95% CI 0.05; 1.00) Gy for males. These improvements are still not sufficient to separate radiation-induced from sporadic PTC cases at very low doses <0.015 Gy typical for the Fukushima accident.

CONCLUSIONS

Successful application of our preferred mechanistic model to LSS incidence data confirms and improves the biological two-path concept of radiation-induced PTC. Model predictions suggest further molecular validation studies to consolidate the basis of biologically-based risk estimation.

Radiation Doses and Risks in Breast Screening

This article describes radiation doses and cancer risks of digital breast imaging technologies used for breast cancer detection. These include digital mammography (DM), digital breast tomosynthesis (DBT), and newer technologies such as contrast-enhanced digital or spectral mammography (CEM), whole-breast computed tomography, breast-specific gamma imaging (BSGI), molecular breast imaging (MBI), and positron emission mammography (PEM). This article describes the basis for radiation risk estimates, compares radiation doses and risks, and provides benefit-to-radiation-risk ratios for different breast imaging modalities that use ionizing radiation. Current x-ray-based screening modalities such as DM and DBT have small to negligible risks of causing radiation-induced cancers in women of normal screening age. Possible new screening modalities such as CEM have similar small cancer risks. Potential screening modalities that involve radionuclide injection such as BSGI, MBI, and PEM have significantly higher cancer risks unless efficient detection systems and reduced administered doses are used. Benefit-to-radiation-risk estimates are highly favorable for screening with DM and other modalities having comparable (or higher) cancer detection rates and comparably low radiation doses.

The Importance of Neurological Examination for the Indication of Computed Tomography of the Brain in Pediatric Emergency Room

Objectives:

In this study, records of the children who underwent Computed Tomography of the Brain (CTB) were reviewed to increase the awareness of pediatricians to protect patients from radiation, whether CTB was used with right indications or if it was determinative for diagnosis.

Methods:

In total, in this study, 342 cases applied to our Pediatric Emergency Polyclinic between January 2005-December 2010 were retrospectively evaluated regarding complaints at admission, neurological examination and CTB results. The sensitivity and specificity of the neurological examination in detecting the CTB pathology was determined.

Results:

The results were normal in 319 of the 342 cases with CBT and abnormal in 23, out of which abnormal CTB results were only in three (0.99%) of the 301 patients with normal neurological examination results and in 20 (48.8%) of 41 patients with abnormal neurological examination results. The difference between the two groups was statistically significant (p=0.001). The sensitivity and specificity of the neurological examination in detecting CTB pathology were 87% and 94%, respectively.

Conclusion:

Detailed neurological examination of the patients in the pediatric emergency department has a key role in determining the indications for CTB. Clinical follow-up should guide neuroradiological imaging in children with normal results of the neurological examination.

Assessment of knowledge and perceptions of medical radiation among caregivers and adolescent patients in the paediatric emergency department

INTRODUCTION

This study aimed to assess understanding of the potential risks associated with medical imaging among caregivers and adolescent patients in a paediatric emergency department (PED) in Singapore.

METHODS

A prospective convenience sample survey was performed involving adolescents and caregivers presenting to our PED from December 2015 to May 2016. The questionnaire examined demographic data, knowledge of imaging procedures and radiation risks, and expectations regarding information provided about medical radiation.

RESULTS

A total of 349 questionnaires were returned (caregivers 82.5%, adolescents 17.5%). A mean of 6.2 ± 2.4 (out of 11) questions were correctly answered. Those who had tertiary education fared better than those who did not (36.4% vs. 17.2% scoring above the mean, p = 0.001). Age, gender, history of previous imaging and imaging performed during the visit did not affect the score. Two-thirds of the participants did not associate medical radiation with any negative lifetime risk of cancers or know that different scans entailed differing amounts of radiation. Most were unaware that the radiation dose in medical imaging is adjusted to a child's size. Among patients who underwent imaging, 90.1% received explanations on the need for scans, and 26.5% were informed of the risks involved. Almost all participants wished to be informed of imaging indications and risks. More preferred to learn this from physicians (75.6%) or technicians (51.6%) rather than through educational pamphlets (34.4%) or Internet resources (22.9%).

CONCLUSION

Awareness regarding medical radiation needs to be improved in our patient population. A mismatch exists between caregiver expectations and the actual procedure of disclosure of the risk associated with radiation.

Organ Doses, Effective Dose, and Cancer Risk From Coronary CT Angiography Examinations

OBJECTIVE. The purposes of this study were to determine organ and effective doses and to estimate the risk of exposure-induced cancer death (REID) associated with coronary CT angiography (CCTA) examinations. SUBJECTS AND METHODS. CCTA examinations were performed in three stages: calcium score, monitoring, and cardiac phases for all patients. Effective dose was calculated using two methods. The first was based on the scanner-derived dose-length product, and the second entailed use of an organ and effective dose calculator software application. Organ doses were calculated on the basis of the tissue weighting factors of International Commission on Radiation Protection report 103. REID values were assessed with a cancer risk estimator software application. RESULTS. The study included 185 patients (95 men, 90 women). For women, breast doses were high at 52.04 ± 14.08 mGy. The mean effective dose in the women was greater than that in the men (24.05 vs 16.30 mSv, p < 0.05). The mean REID values in patients undergoing CCTA with a 64-MDCT scanner were 13.4 per 10,000 men (1 in 746) and 19.6 per 10,000 women (1 in 508). The REID values were considerably higher for the younger women. CONCLUSION. The results of this study will help referring physicians justify requesting CCTA examinations by considering their benefits for diagnosis on the one hand and awareness of the risk of radiation-induced cancer on the other. In the case of CCTA scans that are properly justified by clinical indication, patients and physicians should not be concerned about the radiation risks.

High Cancer Risk in US Naval Personnel Serving in Nuclear Powered Ships

The USA Defense Threat Reduction Agency provided data in 2014 on the health status, including cancer, of the 4,843 sailors on the nuclear-powered United States Ship (USS) Ronald Reagan over the 2.55-year period from May 12, 2011 to Dec 31, 2013. Also provided were data on a matched control group of 65,269 US Navy personnel. Examination of the control population relative to the US national data gives a relative risk for all malignancies of RR = 9.2 (95% CI 8.48 < 9.2 < 9.96). The result suggests a significant cancer risk associated with serving on a nuclear-powered ship, one which is not predicted by the science underlying current radiation protection legislation.

Radiation risk of incident colorectal cancer by anatomical site among atomic bomb survivors: 1958-2009

Radiation effects on colorectal cancer rates, adjusted for smoking, alcohol intake and frequency of meat consumption and body mass index (BMI) by anatomical subsite (proximal colon, distal colon and rectum) were examined in a cohort of 105,444 atomic bomb survivors. Poisson regression methods were used to describe radiation-associated excess relative risks (ERR) and excess absolute rates (EAR) for the 1958-2009 period. There were 2,960 first primary colorectal cancers including 894 proximal, 871 distal and 1,046 rectal cancers. Smoking, alcohol intake and BMI were associated with subsite-specific cancer background rates. Significant linear dose-responses were found for total colon (sex-averaged ERR/Gy for 70 years old exposed at age 30 = 0.63, 95% confidence interval [CI]: 0.34; 0.98), proximal [ERR = 0.80, 95% CI: 0.32; 1.44] and distal colon cancers [ERR = 0.50, 95% CI: 0.04; 0.97], but not for rectal cancer [ERR = 0.023, 95% CI: -0.081; 0.13]. The ERRs for proximal and distal colon cancers were not significantly different (p = 0.41). The ERR decreased with attained age for total colon, but not for proximal colon cancer, and with calendar year for distal colon cancer. The ERRs and EARs did not vary by age at exposure, except for decreasing trend in EAR for proximal colon cancer. In conclusion, ionizing radiation is associated with increased risk of proximal and distal colon cancers. The ERR for proximal cancer persists over time, but that for distal colon cancer decreases. There continues to be no indication of radiation effects on rectal cancer incidence in this population.

Knowledge about imaging modalities, risks, and protection in radiology among medical students at the University of Hail

Aim

The aim of this study was to evaluate awareness and knowledge about radiation risks and safety principles among medical students at the College of Medicine, University of Hail, Hail, Saudi Arabia, in their clinical years.

Materials and Methods

In this cross-sectional study, an anonymous electronic questionnaire was sent to 174 randomly selected students in clinical years 4-6. The questionnaire contained 38 questions. The respondents' answers to these questions were used to classify them according to their demographic characteristics and to evaluate their knowledge about common imaging modalities, radiation risks, and safety measures. The data were analyzed using the Statistical Package for the Social Sciences (SPSS) software, version 22.

Results

Seventy-five (51.7%) of 145 respondents were female and 70 (48.3%) were male. Fifty-five respondents (37.9%) were in year 4, 38 (26.2%) were in year 5, and 52 (35.9%) were in year 6. The mean score for knowledge about common imaging modalities was 4.10 ± 2.030 of 10, that for knowledge about the risks of radiation was 3.17 ± 1.954 (range, 0-8) of 13, and that for knowledge about radiation protection measures was low at 0.79 ± 0.922 (range, 0-4) of 8. Overall, there was an improvement in knowledge about the imaging modalities and the risks of radiation as the number of clinical years increased (P = 0.000), but it was still unsatisfactory.

Conclusion

The results of this study indicate that the medical students at the University of Hail have very limited knowledge about radiation risks and safety measures. These findings highlight the need for urgent action to improve students' knowledge of these topics.

Association Between Prevalence of Peripheral Artery Disease and Radiation Exposure in the Atomic Bomb Survivors

Background

Past reports suggested that total‐body irradiation at 0.5 to 1.0 Gy could be responsible for atherosclerosis. Peripheral artery disease (PAD) is a manifestation of systematic atherosclerosis. Whether the consequences of a low‐to‐moderate dose of radiation include increased risk of PAD remains to be determined. The purpose of this study was to examine the association between radiation exposure and prevalence of PAD among Japanese atomic bomb survivors.

Methods and Results

Radiation exposure from the atomic bombing was assessed in 3476 participants (41.1% men, mean age 74.8 years with SD 6.4 years) with a cross‐sectional survey in 2010 to 2014. Left‐ and right‐side ankle‐brachial indexes and upstroke time (UT) were obtained using oscillometric VP‐2000. PAD was defined as an ankle‐brachial index of 1.0 or less or a prior history related to revascularization. UT was considered a sensitive marker of early‐stage PAD. Association between radiation exposure and PAD or UT was assessed using multivariable regression analyses with adjustment for potential confounding factors. Of 3476 participants, 79 (2.3%) were identified as having prevalent PAD. Multivariate logistic regression analysis indicated that radiation dose was unrelated to PAD prevalence (odds ratio, 0.83; 95% confidence interval [0.57‐1.21]). UT appeared to increase with radiation dose, but the increase was not statistically significant (1.09 ms/Gy; 95% confidence interval [−0.17 to 2.36]).

Conclusions

We found no clear association of radiation dose with PAD, but it remains to be determined whether UT is associated with radiation dose.

Precision Radiotherapy and Radiation Risk Assessment: How Do We Overcome Radiogenomic Diversity?

Precision medicine is a rapidly developing area that aims to deliver targeted therapies based on individual patient characteristics. However, current radiation treatment is not yet personalized; consequently, there is a critical need for specific patient characteristics of both tumor and normal tissues to be fully incorporated into dose prescription. Furthermore, current risk assessment following environmental, occupational, or accidental exposures to radiation is based on population effects, and does not account for individual diversity underpinning radiosensitivity. The lack of personalized approaches in both radiotherapy and radiation risk assessment resulted in the current situation where a population-based model, effective dose, is being used. In this review article, to stimulate scientific discussion for precision medicine in both radiotherapy and radiation risk assessment, we propose a novel radiological concept and metric - the personalized dose and the personalized risk index - that incorporate individual physiological, lifestyle-related and genomic variations and radiosensitivity, outlining the potential clinical application for precision medicine. We also review on recent progress in both genomics and biobanking research, which is promising for providing novel insights into individual radiosensitivity, and for creating a novel conceptual framework of precision radiotherapy and radiation risk assessment.

Communicating Radiation Risk: The Power of Planned, Persuasive Messaging

Every day, health physicists and physicians are expected to communicate effectively with concerned people, but rarely (if ever) are they given training on how to effectively communicate. In an age of social media, this paper presents the relevance of teachings from an ancient Greek philosopher. Aristotle's Rhetoric is still considered one of the most influential works on persuasive messaging. He puts the onus of effective communications on the people with the "true" and "just" information to communicate that information clearly to the audience. By communicating with intention-using the persuasive appeals of ethos, pathos, logos, and storytelling-radiation professionals can speak to their expertise in radiation science, while adapting their instructions, presentations, and communication styles to meet the needs of each type of audience: from scientists to concerned citizens, from doctors to first responders, and beyond.

Inverted C-arm Orientation During Simulated Hip Arthroscopic Surgery

Background

Fluoroscopic guidance is routinely utilized during hip arthroscopic surgery. Previous studies have shown that the C-arm orientation can significantly affect radiation exposure for both the surgeon and the patient during orthopaedic procedures. However, this has not been previously assessed for hip arthroscopic surgery.

Hypothesis

Using an inverted C-arm during hip arthroscopic surgery will reduce radiation exposure to the patient and surgeon.

Study Design

Descriptive laboratory study.

Methods

A simulation study measured scatter radiation during hip arthroscopic surgery performed in the supine position under fluoroscopic guidance with an anthropomorphic pelvic phantom on a radiolucent operating table. Radiation exposure tested 2 different C-arm orientations: standard and inverted. Testing was performed at 6 locations corresponding to the patient, surgeon's neck, surgeon's waist, surgical technician, anesthesiologist, and radiology technician. Statistical analysis was performed using univariate and multivariate analyses assessing radiation exposure between the C-arm orientations. A risk calculation for carcinogenesis was performed based on reported radiation dosages.

Results

Radiation exposure (in mGy/min) was more than 100-fold higher for the patient compared with the surgeon in both C-arm orientations. The inverted C-arm orientation resulted in a 2.48-fold decrease in patient radiation exposure when compared with the standard orientation (10.8 mGy/min vs 26.8 mGy/min, respectively). There was a small but significant increase in surgeon radiation exposure in the inverted orientation compared with the standard orientation (0.072 vs 0.067 mGy/min, respectively). The patient's carcinogenesis risk was decreased 2.64-fold with the inverted orientation compared with the standard orientation (1.4 × 10^-5 vs 3.7 × 10^-5, respectively).

Conclusion

The inverted C-arm orientation resulted in a 2.48-fold decrease in patient radiation exposure with a 2.64-fold decrease in the carcinogenesis risk compared with the standard orientation. Inadvertently, the inverted orientation provided a 9-cm increase in the surgeon's working area. Our data supported the clinical utilization of the inverted C-arm orientation during hip arthroscopic surgery to minimize patient radiation exposure. Although there was a minimal but significant increase in surgeon radiation exposure with the inverted orientation, we believe that this is negligible when incorporated with standard leaded protective equipment as contrasted with the significant dose reduction for the patient as well as the decreased risk of carcinogenesis and hereditary disorders.

Clinical Relevance

Patients undergoing hip arthroscopic surgery routinely acquire radiation exposure during the use of the C-arm. Measures to minimize radiation via the inverted C-arm orientation will decrease the unnecessary risk to the patient while continuing to allow for optimal treatment.

2018 ACC/HRS/NASCI/SCAI/SCCT Expert Consensus Document on Optimal Use of Ionizing Radiation in Cardiovascular Imaging-Best Practices for Safety and Effectiveness, Part 1: Radiation Physics and Radiation Biology: A Report of the American College of Cardiology Task Force on Expert Consensus Decision Pathways Developed in Collaboration With Mended Hearts

The stimulus to create this document was the recognition that ionizing radiation-guided cardiovascular procedures are being performed with increasing frequency, leading to greater patient radiation exposure and, potentially, to greater exposure for clinical personnel. Although the clinical benefit of these procedures is substantial, there is concern about the implications of medical radiation exposure. The American College of Cardiology leadership concluded that it is important to provide practitioners with an educational resource that assembles and interprets the current radiation knowledge base relevant to cardiovascular procedures. By applying this knowledge base, cardiovascular practitioners will be able to select procedures optimally, and minimize radiation exposure to patients and to clinical personnel. Optimal Use of Ionizing Radiation in Cardiovascular Imaging: Best Practices for Safety and Effectiveness is a comprehensive overview of ionizing radiation use in cardiovascular procedures and is published online. To provide the most value to our members, we divided the print version of this document into 2 focused parts. Part I: Radiation Physics and Radiation Biology addresses the issue of medical radiation exposure, the basics of radiation physics and dosimetry, and the basics of radiation biology and radiation-induced adverse effects. Part II: Radiological Equipment Operation, Dose-Sparing Methodologies, Patient and Medical Personnel Protection covers the basics of operation and radiation delivery for the 3 cardiovascular imaging modalities (x-ray fluoroscopy, x-ray computed tomography, and nuclear scintigraphy) and will be published in the next issue of the Journal.

Probability Distribution of Dose and Dose-Rate Effectiveness Factor for use in Estimating Risks of Solid Cancers From Exposure to Low-Let Radiation

This paper presents an analysis to develop a subjective state-of-knowledge probability distribution of a dose and dose-rate effectiveness factor for use in estimating risks of solid cancers from exposure to low linear energy transfer radiation (photons or electrons) whenever linear dose responses from acute and chronic exposure are assumed. A dose and dose-rate effectiveness factor represents an assumption that the risk of a solid cancer per Gy at low acute doses or low dose rates of low linear energy transfer radiation, RL, differs from the risk per Gy at higher acute doses, RH; RL is estimated as RH divided by a dose and dose-rate effectiveness factor, where RH is estimated from analyses of dose responses in Japanese atomic-bomb survivors. A probability distribution to represent uncertainty in a dose and dose-rate effectiveness factor for solid cancers was developed from analyses of epidemiologic data on risks of incidence or mortality from all solid cancers as a group or all cancers excluding leukemias, including (1) analyses of possible nonlinearities in dose responses in atomic-bomb survivors, which give estimates of a low-dose effectiveness factor, and (2) comparisons of risks in radiation workers or members of the public from chronic exposure to low linear energy transfer radiation at low dose rates with risks in atomic-bomb survivors, which give estimates of a dose-rate effectiveness factor. Probability distributions of uncertain low-dose effectiveness factors and dose-rate effectiveness factors for solid cancer incidence and mortality were combined using assumptions about the relative weight that should be assigned to each estimate to represent its relevance to estimation of a dose and dose-rate effectiveness factor. The probability distribution of a dose and dose-rate effectiveness factor for solid cancers developed in this study has a median (50th percentile) and 90% subjective confidence interval of 1.3 (0.47, 3.6). The harmonic mean is 1.1, which implies that the arithmetic mean of an uncertain estimate of the risk of a solid cancer per Gy at low acute doses or low dose rates of low linear energy transfer radiation is only about 10% less than the mean risk per Gy at higher acute doses. Data were also evaluated to define a low acute dose or low dose rate of low linear energy transfer radiation, i.e., a dose or dose rate below which a dose and dose-rate effectiveness factor should be applied in estimating risks of solid cancers.

Typical doses and dose rates in studies pertinent to radiation risk inference at low doses and low dose rates

In order to quantify radiation risks at exposure scenarios relevant for radiation protection, often extrapolation of data obtained at high doses and high dose rates down to low doses and low dose rates is needed. Task Group TG91 on 'Radiation Risk Inference at Low-dose and Low-dose Rate Exposure for Radiological Protection Purposes' of the International Commission on Radiological Protection is currently reviewing the relevant cellular, animal and human studies that could be used for that purpose. This paper provides an overview of dose rates and doses typically used or present in those studies, and compares them with doses and dose rates typical of those received by the A-bomb survivors in Japan.

Diversity of Concerns in Recovery after a Nuclear Accident: A Perspective from Fukushima

Since the 2011 Fukushima nuclear accident, tremendous resources have been devoted to recovery, and the Japanese Government is gradually lifting evacuation orders. However, public concerns remain prevalent, affecting some people's return to a normal life and threatening their well-being. This study reviews government reports, academic papers, newspaper articles and conference presentations with the aim of obtaining a better understanding of issues which relate to radiation concerns in the recovery process in the aftermath of the accident. It looks extensively at: (1) the current status of the post-accident operations and existing radiation issues in Fukushima, and (2) approaches taken to engage the public during recovery from five previous comparable nuclear and radiological events: Three Mile Island, Buenos Aires (RA-2 facility), Chernobyl, Goiânia and Tokai-mura. The findings indicate that the limitations and emerging challenges of the current recovery operations cause concerns about radiation exposure in various aspects of day-to-day life. Past experiences suggest that long-term management that take a holistic and cohesive approach is critical for restoration of sustainable livelihoods and for social re-integration. Not only actual risks but also public perceptions of risks should be carefully assessed and addressed in the process of environmental remediation.

Review of the Global Solar UV Index 2015 Workshop Report

The Global Solar UV Index was developed as an easy-to-understand measure of the amount of biologically-effective ambient solar ultraviolet radiation (UVR) at different locations on the earth's surface. Over the past few years, questions have been raised about the global applicability of the UV Index, about the evidence base for exposure risk thresholds and related protective measures, and about whether the overall impact of the UV Index could be improved with modifications. An international workshop was organized by several organizations, including the World Health Organization, to assess if current evidence was sufficiently strong to modify the UV Index and to discuss different ways it might be improved in order to influence sun-protective behavior. While some animal research suggests there may be no threshold effect, the relative importance of sub-erythemal doses of sunlight in causing skin cancer in humans remains unknown. Evidence suggests that regular use of sunscreen can prevent skin cancer and that sunglasses are an effective method of protecting the eyes from solar UVR. The UV Index as a risk communication tool continues to be useful for raising awareness and to support sun-protection behavior. Although there was agreement that guidance on the use of the UV Index could be improved, the workshop participants identified that strong health outcome-based human evidence would be needed as the basis for a revision. For the UV Index to be relevant in as many countries as possible, it should continue to be adapted to suit local conditions.

Radiation Risk to the Fluoroscopy Operator and Staff

OBJECTIVE

Recent articles discussing cases of brain cancer in interventionalists have raised concerns regarding the hazards of occupational exposure to ionizing radiation. We review the basics of radiation dose and the potential radiation effects, particularly as they pertain to the operator. Then we present the data regarding the risk of each type of radiation effect to the fluoroscopy operator and staff, with special attention on cancer induction, radiation-induced cataracts, and the pregnant operator.

CONCLUSION

Although the evidence overwhelmingly shows that exposure to higher doses of radiation carries a risk of cancer and tissue reactions, the risks of chronic exposure to low-level radiation are less clear. Many studies examining occupational exposure to radiation fail to show an increased risk of stochastic effects of radiation, but the positive results raise concern that the studies are underpowered to consistently detect the small risk. The lack of information in these studies about radiation doses and adherence to radiation protection further confound their interpretation. Large prospective studies of populations with occupational exposure to low-level radiation might clarify this issue. More clearly established are the risks of radiation to the fetus and the risk of cataracts in interventional cardiologists and interventional radiologists. Interventionalists can mitigate these risks by following established radiation safety practices.

Long-Term Outcomes of Patients With Mediastinal Radiation-Associated Severe Aortic Stenosis and Subsequent Surgical Aortic Valve Replacement: A Matched Cohort Study

BACKGROUND

Cardiac disease after mediastinal radiotherapy for thoracic malignancy (chest radiotherapy [XRT]) often manifests as progressive aortic stenosis. In patients with XRT-induced severe aortic stenosis undergoing surgical aortic valve replacement (SAVR), we sought to: (1) study long-term survival and compare these patients with a matched cohort undergoing SAVR during the same time frame; and (2) identify potential predictors of long-term mortality.

METHODS AND RESULTS

We studied patients with symptomatic severe aortic stenosis undergoing SAVR at our institution, of which there were 172 mediastinal XRT patients (63±13 years, 62% women) matched in a 1:1 fashion (based on age, sex, time of surgery, and aortic valve area) with 172 non-XRT patients (comparison group). Baseline clinical and postoperative data were obtained. Society of Thoracic Surgeons score was calculated and mortality was recorded. In the XRT group, the median Society of Thoracic Surgeons score was 4% (interquartile range 2-13), while mean left ventricular ejection fraction, left ventricular stroke volume index, and mean aortic valve gradient were 54±11%, 38±14 mL/m2, and 39±11 mm Hg, respectively. In the entire cohort, 27% and 34% of patients underwent concomitant coronary artery bypass grafting and aortic surgery at the time of SAVR, respectively. Thirty-day/in-hospital deaths occurred in 4 (2%) patients in the XRT group and 0 patients in the comparison group. At 6±3 years of follow-up, on matched group analysis, there were 95 (28%) deaths (83 [48%] in the XRT group versus 12 [7%] in the comparison group (log-rank 89, P<0.001). On multivariable Cox survival analysis, in the whole cohort, higher Society of Thoracic Surgeons score (hazard ratio, 1.14; 95% CI, 1.03-1.26) and mediastinal XRT (hazard ratio, 8.12; 95% CI, 4.26-15.64) were associated with increased longer-term mortality (both P<0.01).

CONCLUSIONS

In patients with severe aortic stenosis undergoing SAVR, patients with prior mediastinal XRT have significantly worse longer-term survival versus a matched cohort.