Cancer risks attributable to low doses of ionizing radiation: assessing what we really know

UNIVERSAL RADIATION PROTECTION SYSTEM (URPS); A NATURAL GLOBAL STANDARDISED TREND FOR HUMAN EXPOSURE CONTROL IN 21st CENTURY

In order to address the many deficiencies with current radiological protection system worldwide, this paper proposes a new Universal Radiation Protection System (URPS) Hypothesis with novel philosophy, concepts and methodologies of applying principles of equal human health-effect risks of an individual per unit radiation dose either from environmental natural background (NBG) or man-made sources; a 'standardised integrated dose system' for integrating all individual doses with emphasis on national NBG doses; considering worker as a member of public; and a 'cause-effect conservation principle' for epidemiology risk estimation. The URPS also a radiation hypothesises fractionation weighting factors (WF); a 'URPS Model' for bridging 'linear no-threshold and hormesis models'; example dose limit for workers; as well as new terms and definitions. State-of-the-art developments on URPS hypothesis are presented and discussed with simple global natural trends for standardised human exposure control in order to protect workers, patients, public and environment by standardised methods independent of source and country of origin in the 21st century.

Clinical and epidemiological observations on individual radiation sensitivity and susceptibility

Purpose: To summarize existing knowledge and to understand individual response to radiation exposure, the MELODI Association together with CONCERT European Joint Programme has organized a workshop in March 2018 on radiation sensitivity and susceptibility.Methods: The workshop reviewed the current evidence on this matter, to inform the MELODI Strategic Research Agenda (SRA), to determine social and scientific needs and to come up with recommendations for suitable and feasible future research initiatives to be taken for the benefit of an improved medical diagnosis and treatment as well as for radiation protection.Results: The present paper gives an overview of the current evidence in this field, including potential effect modifiers such as age, gender, genetic profile, and health status of the exposed population, based on clinical and epidemiological observations.Conclusion: The authors conclude with the following recommendations for the way forward in radiation research: (a) there is need for large (prospective) cohort studies; (b) build upon existing radiation research cohorts; (c) use data from well-defined cohorts with good exposure assessment and biological material already collected; (d) focus on study quality with standardized data collection and reporting; (e) improve statistical analysis; (f) cooperation between radiobiology and epidemiology; and (g) take consequences of radiosensitivity and radiosusceptibility into account.

Size-specific dose estimations for pediatric chest, abdomen/pelvis and head CT scans with the use of GATE

PURPOSE

The purpose of this study is to create an organ dose database for pediatric individuals undergoing chest, abdomen/pelvis, and head computed tomography (CT) examinations, and to report the differences in absorbed organ doses, when anatomical differences exist for pediatric patients.

METHODS

The GATE Monte Carlo (MC) toolkit was used to model the GE BrightSpeed Elite CT model. The simulated scanner model was validated with the standard Computed Tomography Dose Index (CTDI) head phantom. Twelve computational models (2.1-14 years old) were used. First, contributions to effective dose and absorbed doses per CTDI_vol and per 100 mAs were estimated for all organs. Then, doses per CTDI_vol were correlated with patient model weight for the organs inside the scan range for chest and abdomen/pelvis protocols. Finally, effective doses per dose-length product (DLP) were estimated and compared with the conventional conversion k-factors.

RESULTS

The system was validated against experimental CTDI_w measurements. The doses per CTDI_vol and per 100 mAs for selected organs were estimated. The magnitude of the dependency between the dose and the anatomical characteristics was calculated with the coefficient of determination at 0.5-0.7 for the internal scan organs for chest and abdomen/pelvis protocols. Finally, effective doses per DLP were compared with already published data, showing discrepancies between 13 and 29% and were correlated strongly with the total weight (R² > 0.8) for the chest and abdomen protocols.

CONCLUSIONS

Big differences in absorbed doses are reported even for patients of similar age or same gender, when anatomical differences exist on internal organs of the body.

Association of Exposure to Diagnostic Low-Dose Ionizing Radiation With Risk of Cancer Among Youths in South Korea

IMPORTANCE

Diagnostic low-dose ionizing radiation has great medical benefits; however, its increasing use has raised concerns about possible cancer risks.

OBJECTIVE

To examine the risk of cancer after diagnostic low-dose radiation exposure.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study included youths aged 0 to 19 years at baseline from South Korean National Health Insurance System claim records from January 1, 2006, to December 31, 2015. Exposure to diagnostic low-dose ionizing radiation was classified as any that occurred on or after the entry date, when the participant was aged 0 to 19 years, on or before the exit date, and at least 2 years before any cancer diagnosis. Cancer diagnoses were based on International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes. Data were analyzed from March 2018 to September 2018.

MAIN OUTCOMES AND MEASURES

The primary analysis assessed the incidence rate ratios (IRRs) for exposed vs nonexposed individuals using the number of person-years as an offset.

RESULTS

The cohort included a total of 12 068 821 individuals (6 339 782 [52.5%] boys). There were 2 309 841 individuals (19.1%) aged 0 to 4 years, 2 951 679 individuals (24.5%) aged 5 to 9 years, 3 489 709 individuals (28.9%) aged 10 to 14 years, and 3 317 593 individuals (27.5%) aged 15 to 19 years. Of these, 1 275 829 individuals (10.6%) were exposed to diagnostic low-dose ionizing radiation between 2006 and 2015, and 10 792 992 individuals (89.4%) were not exposed. By December 31, 2015, 21 912 cancers were recorded. Among individuals who had been exposed, 1444 individuals (0.1%) received a cancer diagnosis. The overall cancer incidence was greater among exposed individuals than among nonexposed individuals after adjusting for age and sex (IRR, 1.64 [95% CI, 1.56-1.73]; P < .001). Among individuals who had undergone computed tomography scans in particular, the overall cancer incidence was greater among exposed individuals than among nonexposed individuals after adjusting for age and sex (IRR, 1.54 [95% CI, 1.45-1.63]; P < .001). The incidence of cancer increased significantly for many types of lymphoid, hematopoietic, and solid cancers after exposure to diagnostic low-dose ionizing radiation. Among lymphoid and hematopoietic cancers, incidence of cancer increased the most for other myeloid leukemias (IRR, 2.14 [95% CI, 1.86-2.46]) and myelodysplasia (IRR, 2.48 [95% CI, 1.77-3.47]). Among solid cancers, incidence of cancer increased the most for breast (IRR, 2.32 [95% CI, 1.35-3.99]) and thyroid (IRR, 2.19 [95% CI, 1.97-2.20]) cancers.

CONCLUSIONS AND RELEVANCE

This study found an association of increased incidence of cancer with exposure to diagnostic low-dose ionizing radiation in a large cohort. Given this risk, diagnostic low-dose ionizing radiation should be limited to situations in which there is a definite clinical indication.

Cone-Beam Computed Tomography in Orthodontics

Unlike patients receiving implants or endodontic treatment, most orthodontic patients are children who are particularly sensitive to ionizing radiation. Cone-beam computed tomography (CBCT) carries risks and benefits in orthodontics. The principal risks and limitations include ionizing radiation, the presence of artifacts, higher cost, limited accessibility, and the need for additional training. However, this imaging modality has several recognized indications in orthodontics, such as the assessment of impacted and ectopic teeth, assessment of pharyngeal airway, assessment of mini-implant sites, evaluation of craniofacial abnormalities, evaluation of sinus anatomy or pathology, evaluation of root resorption, evaluation of the cortical bone plate, and orthognathic surgery planning and evaluation. CBCT is particularly justified when it brings a benefit to the patient or changes the outcome of the treatment when compared with conventional imaging techniques. Therefore, CBCT should be considered for clinical orthodontics for selected patients. Prescription of CBCT requires judicious and sound clinical judgment. The central question of this narrative review article is: when does CBCT add value to the practice of orthodontics? To answer this question, this article presents discussion on radiation dosage of CBCT and other imaging techniques used in orthodontics, limitations of CBCT in orthodontics, justifying the use of CBCT in orthodontics, and the benefits and evidence-based indications of CBCT in orthodontics. This review summarizes the central themes and topics in the literature regarding CBCT in orthodontics and presents ten orthodontic cases in which CBCT proved to be valuable.

The role of physics in radioecology and radiotoxicology

This article gives an overview of physical concepts important for radioecology and radiotoxicology to help bridge a gap between non-physicists in these scientific disciplines and the intricate language of physics. Relying on description and only as much mathematics as necessary, we discuss concepts ranging from fundamental natural forces to applications of physical modelling in phenomenological studies. We first explain why some atomic nuclei are unstable and therefore transmute. Then we address interactions of ionising radiation with matter, which is the foundation of both radioecology and radiotoxicology. We continue with relevant naturally occurring and anthropogenic radionuclides and their properties, abundance in the environment, and toxicity for the humans and biota. Every radioecological or radiotoxicological assessment should take into account combined effects of the biological and physical half-lives of a radionuclide. We also outline the basic principles of physical modelling commonly used to study health effects of exposure to ionising radiation, as it is applicable to every source of radiation but what changes are statistical weighting factors, which depend on the type of radiation and exposed tissue. Typical exposure doses for stochastic and deterministic health effects are discussed, as well as controversies related to the linear no-threshold hypothesis at very low doses.

Towards a New Concept of Low Dose

When people discuss the risks associated with low doses of ionizing radiation, central to the discussion is the definition of a low dose and the nature of harm. Standard answers such as "doses below 0.1 Gy are low" or "cancer is the most sensitive measure of harm" obscure the complexity within these seemingly simple questions. This paper will discuss some of the complex issues involved in determining risks to human and nonhuman species from low-dose exposures. Central to this discussion will be the role of communicable responses to all stressors (often referred to as bystander responses), which include recently discovered epigenetic and nontargeted mechanisms. There is a growing consensus that low-dose exposure to radiation is but one of many stressors to impact populations. Many of these stressors trigger responses that are generic and not unique to radiation. The lack of a unique radiation signature makes absolute definition of radiation risk difficult. This paper examines a possible new way of defining low dose based on the systemic response to the radiation. Many factors will influence this systemic response and, because it is inherently variable, it is difficult to predict and so makes low-dose responses very uncertain. Rather than seeking to reduce uncertainty, it might be valuable to accept the variability in outcomes, which arise from the complexity and multifactorial nature of responses to stressors.

The Diagnostic Accuracy of Ultrasound in Detecting Distal Radius Fractures in a Pediatric Population

OBJECTIVE

Sports ultrasound (US) is becoming popular in diagnosing musculoskeletal injuries. This study, also called the Pediatric Distal Radius Ultrasound Study (PeDRUS), compared the diagnostic accuracy of sports US with plain radiographs in possible distal radius buckle fractures in pediatric population.

METHODS

In this prospective observational study, patients (2-15 years) presenting to an outpatient orthopedic injury clinic with distal forearm injuries without deformity were recruited. Bedside ultrasonography was performed and interpreted by the investigators as positive or negative for fracture. Plain radiographs were then performed and interpreted by the same investigator. The radiographs were considered the definitive imaging study for this investigation.

RESULTS

Fifty-one patients were included with a mean age of 9.9 years. Fractures were diagnosed on both US and plain radiographs in 34 patients. Fractures were ruled out on both US and plain radiographs in 16 patients. There was only one case in which the US was interpreted differently than radiograph. For fractures of the distal radius in this population, the sensitivity was 97.1% [95% confidence interval (CI) = 89.2-97.1] and the specificity was 100% (95% CI = 82.5-100). The positive predictive value was 100% (95% CI = 91.8-100), whereas the negative predictive value was 94.1% (95% CI = 77.7-94.1). The positive likelihood ratio was infinite, suggesting utility in confirming a fracture. The negative likelihood ratio was 0.03 (95% CI = 0.03-0.13), suggesting that US has value in ruling out a fracture.

CONCLUSIONS

Our study suggests that diagnostic sports US is sensitive and specific for detecting distal radius fractures in pediatric patients with nondeformed forearm injuries, demonstrating that US is an acceptable alternative to plain radiographs for evaluating fractures in a pediatric population.

Improving patient and staff safety by minimising radiation exposure during trauma surgery: A simple and validated predictive model

INTRODUCTION

Minimising radiation exposure, from fluoroscopic equipment during trauma surgery is crucial to safe-guarding patients and staff. This aim of this study was to identify variables associated with increased radiation exposure for 3 of the most common trauma procedures. Secondly, we aimed to derive an internally and externally validated mathematical model for predicting radiation exposure for these procedures.

MATERIALS AND METHODS

We prospectively recorded radiation exposure from 270 sliding hip screw (SHS), ankle and wrist fixation procedures. Patient demographics, fracture severity, surgeon and radiographer grade were assessed using univariate and multivariate analyses. A mathematical model was then created and externally assessed for validity from another unit.

RESULTS

With regards to the analysis of radiation exposure when fixing wrist fractures, a significant regression equation was found (F (3, 86) = 62.2, p < 0.001), with an adjusted R² of 0.69. Patients' predicted radiation exposure (cGY/cm2) was therefore equal to the positive result of: 81.916(Fracture severity) + 43.426(Surgical grade) + 23.490 (radiographer grade)-203.89.With regards to the analysis of radiation exposure when fixing ankle fractures, a significant regression equation was found, (F (3, 83) = 15.49, p < 0.001), with an adjusted R² of 0.34. Patients' predicted radiation exposure (cGY/cm2) was therefore equal to the positive result of: 39.541(Fracture severity) + 51.937(Surgical grade) + 37.702 (radiographer grade)-124.558 SHS (F (3, 89) = 25.29, p < 0.001), R² of 0.44.61.338(Fracture severity) + 60.945(Surgical grade) + 35.491 (radiographer grade)-105.501. These predictive models were successfully externally validated.

CONCLUSION

This study has demonstrated a workable and externally validated model for accurately predicting the likely radiation exposure using common and easily collectable variables. These models could be used to modify practuce and minimise the radiation exposure to patients and staff.

Oxidized Cell-Free DNA Is a Factor of Stress Signaling in Radiation-Induced Bystander Effects in Different Types of Human Cells

In pathology or under damaging conditions, the properties of cell-free DNA (cfDNA) change. An example of such change is GC enrichment, which drastically alters the biological properties of cfDNA. GC-rich cfDNA is a factor of stress signaling, whereas genomic cfDNA is biologically inactive. GC-rich cfDNA stimulates TLR9-MyD88-NF-κB signaling cascade, leading to an increase in proinflammatory cytokine levels in the organism. In addition, GC-rich DNA is prone to oxidation and oxidized cfDNA can stimulate secondary oxidative stress. This article is a review of works dedicated to the investigation of a low-dose ionizing radiation effect, a bystander effect, and the role of cfDNA in both of these processes.

An Estimation of Lifetime Fatal Carcinogenesis Risk Attributable to Radiation Exposure in the First Year Following Polytrauma: A Major Trauma Center's Experience Over 10 Years

BACKGROUND

The utilization of medical imaging continues to rise, including routine use in major trauma centers. The aims of this study were to estimate the amount of radiation exposure from radiographic imaging and the associated fatal carcinogenesis risk among patients treated for polytrauma at 1 institution.

METHODS

Included were patients who were admitted to our institution with an Injury Severity Score (ISS) of ≥16 during the period of January 2007 to December 2016. Records of patients were reviewed to assess exposures to radiation (excluding fluoroscopy) in the 12 months following injury. The risk of developing a fatal cancer of any type was modeled using patient age and sex, on the basis of the International Commission on Radiological Protection (ICRP) recommendations. Estimates of cancer risk were based on the exposure received and then imported into previously developed models.

RESULTS

Overall, 2,394 patients, with a mean ISS of 28.66 (range, 17 to 66), were included in our analysis. The mean total radiation dose received was 30.45 mSv and the median dose was 18.46 mSv. One hundred and fifteen patients (4.8% of the cohort) received ≥100 mSv of radiation. The total patient group had a 3.56% mean risk of fatal carcinogenesis of any type that related solely to medical exposure of radiation as a result of their injuries. In their lifetime, 85 patients would be expected to develop cancer as a result of medical imaging that they had undergone in the year following their accident. The ISS and the body region of injury contributing to the ISS were predictive of the level of radiation exposure.

CONCLUSIONS

Those involved in trauma care can use the ISS and body region to predict radiation exposure and the risk of fatal carcinogenesis of any type. We found that, for injuries to the limb and pelvis, the greater the severity of injury, the greater the radiation exposure and fatal carcinogenesis risk. However, this study does not provide an actuarial analysis. It is unknown how many patients in the study went on to develop cancer.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Incidental Findings in Dental Radiology are Concerning for Family Doctors

Cone Beam Computerized Tomography (CBCT) is an imaging technology increasingly used in dentistry. Depending on the size of the examination area, visualization of anatomical structures outside the indication area may reveal incidental findings (IF). The aims of this systematic review and meta-analysis were to 1) evaluate the frequency, location and different types of incidental findings (IF) revealed during CBCT examinations; 2) identify potential influencing factors such as gender or age; 3) highlight what the family doctor should know about CBCT and the benefits for medical care.

70 retrospective studies were included. 60% of IF are in the naso-oropharyngeal airway and paranasal sinuses. Carotid calcifications were observed with a mean prevalence of 9% CI95% [2-21]). Meta-regression showed a significant association of this prevalence with age, irrespective of gender.

Given the high frequency of IF, with varying severity, the whole medical community is fully involved, and its opinion should be sought to ensure the best possible management for the patients. Physicians may also require CBCT examinations that would have been previously prescribed by a dentist, that may serve to better orientate investigations toward another imaging technique. The family doctor is therefore the dentist’s main interlocutor and the main coordinator of the follow-up of IF.

Relationship between viability and genotoxic effect of gamma rays delivered at different dose rates in somatic cells of Drosophila melanogaster

The role of dose rate (DR) on biological effects of ionizing radiation is an area of significant research focus and relevant to environmental exposures. The present investigation was aimed to examine the direct relationship between viability and genotoxicity in Drosophila melanogaster, induced by gamma rays in a range of doses from 2 to 35 Gy administered at three different DR. Results indicated that larval-adult viability was reduced in relation to dose but not DR. No marked differences were found in the LD₅₀ produced by differing DR tested. Frequencies of somatic mutation and recombination increased in direct correlation with dose and DR. Data demonstrate the importance of determination of the relationship between viability and genotoxicity induced by DR in in vivo systems for toxicological and radioprotection studies.

The risk of cancer attributable to diagnostic medical radiation: Estimation for France in 2015

Although medical ionizing radiation (IR) has clear clinical benefits, it is an established carcinogen. Our study estimates the number of new cancer cases in France in 2015 attributable to IR exposure from medical procedures. Exposures from external (X-rays, CT scans, interventional radiology) and internal (nuclear medicine) sources were considered. We used 2007 national frequencies of diagnostic examinations by sex and age to estimate the lifetime organ dose exposure adjusted for changes in the use of such procedures over time. The Biological Effects of Ionizing Radiation VII risk models were used to estimate the corresponding excess cancer risk, assuming an average latency period of 10 years. Additionally, we used cancer incidence data from the French Cancer Registries Network. Of the 346,000 estimated new cancer cases in adults in France in 2015, 2300 cases (940 among men and 1360 among women) were attributable to diagnostic IR, representing 0.7% of all new cancer cases (0.5% for men and 0.9% for women). The leading cancers attributable to medical IR were female breast (n = 560 cases), lung (n = 500 cases) and colon (n = 290 cases) cancers. Compared to other risk factors, the contribution of medical IR to the cancer burden is small, and the benefits largely outweigh its harms. However, some of these IR-associated cancer cases may be preventable through dose optimization of and enhanced justification for diagnostic examinations.

Diagnostic Radiation Exposure in Patients with Inflammatory Bowel Disease

BACKGROUND

Because of the chronic and relapsing nature of inflammatory bowel disease (IBD), which often requires characterization with CT scan, IBD patients might be exposed to a large amount of radiation. As a cumulative effective dose (CED) ≥ 100 mSv is considered significant for stochastic risks of cancer, it is important to monitor and control the radiation exposure of the IBD patients. In the present work, we aimed to quantify the mean CED in IBD patients to assess any harmful effects of radiation.

METHODS

This study includes 200 IBD patients, identified retrospectively, from the outpatient clinics of the Centre Hospitalier de l'Université de Montréal between January 1, 2010, and February 15, 2017, from the gastroenterologists' patients lists. The number and type of each radiology test performed were listed for each patient during the study period and the CED was calculated using our institution's dose index when available and standardized tables.

RESULTS

Among the 200 IBD patients, 157 patients had Crohn's disease (CD), 41 had ulcerative colitis (UC), and 2 had indeterminate colitis. The mean CED for IBD patients was 23.1 ± 45.2 mSv during a mean follow-up duration of 4.3 years. CED was higher among patients with CD than with UC (27.5 ± 49.5 versus 6.8 ± 14.8 mSv; p<0.01). Six patients were exposed to a high CED (>100 mSv) and all had CD.

CONCLUSION

While potentially harmful levels of radiation exposure are of concern in only a small number of patients, strategies to limit such exposure are encouraged when clinically appropriate.

The Two-Point Technique for Fluoroscopic-Guided Endoscopic Procedures in Urology: A Validation Study

Introduction: The widespread use of diagnostic and therapeutic ionizing radiation raises concerns regarding excessive occupational and patient exposure. In this study, we test a novel fluoroscopic technique that has the potential to minimize radiation dose during urologic procedures. Materials and Methods: A prospective evaluation of all patients undergoing endoscopic urologic procedures in our institution was conducted. A "two-point technique (TPT)" is described in which the fluoroscope image intensifier (c-arm) is shifted between caudal and cephalad set points of the operative field. We wished to determine whether patient radiation exposure was lower with TPT than with a non-structured conventional technique, referred to as the cognitive fluoroscopic technique (CFT), in which the manipulation of the c-arm was at the discretion of the user. We obtained all clinical, radiographic, and fluoroscopic data of patients in the study period and used unpaired nonparametric statistical analysis of univariates entered stepwise into a logistic regression model. Results: A total of 106 endoscopic urologic procedures from January 2016 to November 2018 were reviewed. Forty-four (41.5%) cases were performed using TPT and 62 (58.5%) using CFT. The mean fluoroscopy time of TPT vs CFT was 71.1 (±60.8) seconds vs 104.5 (±91.6) seconds, respectively (p = 0.04), and the mean radiation dose on TPT vs CFT was 11.6 (±10.6) mGy vs 20.3 (±24.3) mGy, respectively (p = 0.03). TPT was an independent predictor of reduced operative room (OR) time and fluoro time (p < 0.05), while body mass index, age, and operator were not. Conclusion: The "TPT" helps reducing radiation dose and fluoroscopic time during endoscopic urologic procedures. The TPT is useful to lower radiation exposure to patients and OR staff.

Determination of contrast-detail curves in mammography image quality assessment by a parametric model observer

A novel approach is proposed for the determination of contrast-detail curves in mammography image quality assessment. The approach is compared with current practice using virtual mammography. A binary parametric model observer is applied to images of the CDMAM phantom. The observer accounts for the simple disc shaped objects in the phantom and is applied separately to each cell of the phantom. For each of these applications, the area under the ROC curve (AUC) of the model observer is determined. The different AUCs, calculated from different applications of the parametric model observer, are then combined to a single contrast-detail curve quantifying the ability of the observer to detect details in the images. Virtual mammography is developed as a tool to simulate X-ray images of single CDMAM cells and to quantitatively assess the approach in comparison with current practice. It is shown that the proposed approach can lead to similar contrast-detail curves as current practice. The precision of the estimated contrast-detail curves is increased, i.e. using 5 images yields about the same precision for the proposed approach as 16 images when applying current practice. We conclude that contrast-detail curves in mammography image quality assessment can also be determined through the AUC of a binary parametric model observer. Since the proposed approach has higher precision than current practice, it is a promising candidate for contrast-detail analysis in mammography image quality assessment.

Premaxilla: up to which age it remains separated from the maxilla by a suture, how often it occurs in children and adults, and possible clinical and therapeutic implications: Study of 1,138 human skulls

Objective:

To evaluate topographic and temporal aspects of premaxillary bone and premaxillary-maxillary suture, since they are fundamental anatomical elements little explored clinically.

Methods:

1,138 human dry skulls were evaluated, of which 116 (10.19%) of the specimens were children, and 1,022 (89.81%) were adults. The skulls were photographed and the percentage of premaxillary-maxillary suture opening was determined. Subsequently the data were tabulated and submitted to statistical analysis, adopting a level of significance of 5%.

Results:

The progression of premaxillary suture closure from birth to 12 years of age was 3.72% per year. In 100% of the skulls up to 12 years, the premaxillary-maxillary suture open in the palatal region was observed, while 6.16% of adults presented different degrees of opening.

Conclusions:

The premaxilla exists in an independent way within the maxillary complex and the presence of the premaxilla-maxillary suture justifies the success of anteroposterior expansions to stimulate the growth of the middle third of the face, solving anatomical and functional problems.

ANALYTICAL MODEL TO ESTIMATE EQUIVALENT DOSE FROM INTERNAL NEUTRONS IN PROTON THERAPY OF CHILDREN WITH INTRACRANIAL TUMORS

This study developed a computationally efficient and easy-to-implement analytical model to estimate the equivalent dose from secondary neutrons originating in the bodies ('internal neutrons') of children receiving intracranial proton radiotherapy. A two-term double-Gaussian mathematical model was fit to previously published internal neutron equivalent dose per therapeutic absorbed dose versus distance from the field edge calculated using Monte Carlo simulations. The model was trained using three intracranial proton fields of a 9-year-old girl. The resulting model was tested against two intracranial fields of a 10-year-old boy by comparing the mean doses in organs at risk of a radiogenic cancer estimated by the model versus those previously calculated by Monte Carlo. On average, the model reproduced the internal neutron organ doses in the 10-year-old boy within 13.5% of the Monte Carlo at 3-10 cm from the field edge and within a factor of 2 of the Monte Carlo at 10-20 cm from the field edge. Beyond 20 cm, the model poorly estimated H/DRx, however, the values were very small, at <0.03 mSv Gy-1.

Ultrasound guidance for transforaminal percutaneous endoscopic lumbar discectomy may prevent radiation exposure: A case report

BACKGROUND

Percutaneous endoscopic lumbar discectomy (PELD) has become a mature and mainstream minimally invasive surgical technique for treating lumbar disc herniation (LDH). Repeated fluoroscopy, with more than 30 shots on average, is inevitable to ensure its accuracy and safety. However, exposure to X-rays may pose a threat to human health. We herein report a case of ultrasound (US)-assisted PELD in two levels of LDH to explore a new possibility that can reduce the radiation dose during puncture and cannulation in PELD.

CASE SUMMARY

A 38-year-old man with low back pain and left leg pain for more than 7 years came to our clinic, his symptoms had aggravated for 1 month, and he was diagnosed with L3-4 and L4-5 disc herniations. He received US-guided PELD with good results: His straight leg elevation increased from 40 to 90 degrees after PELD, and his visual analog scale (VAS) and Oswestry Disability Index scores both significantly decreased immediately and 6 mo after PELD. With the guidance of US, he received only two shots of fluoroscopy (fluoroscopic time: 4.4 s; radiation dose: 3.98 mGy). To our knowledge, this is the first case of US-guided puncture and cannulation of PELD for LDH at two levels.

CONCLUSION

US could be used to guide PELD and has the potential to largely reduce radiation than traditional X-ray guidance.

Cardiovascular and growth outcomes of C57Bl/6J mice offspring exposed to maternal stress and ionizing radiation during pregnancy

Purpose: Developmental programming involves an adverse intrauterine environment which can result in offspring phenotype changes following birth. The developmental programming of hypertension has been reported to possibly involve oxidative stress at the cellular level. Ionizing radiation produces oxidative stress, even at low doses, and irradiation of animals is often coupled with potential sources of maternal stress such as transportation of animals or repeated handling. Materials and methods: Pregnant C57Bl/6J mice were irradiated on gestational day 15 with 5-1000 mGy ¹³⁷Cs gamma radiation. Post-natal weight, blood pressure (BP) and heart rate (HR) were measured. Radiation had minimal effects at doses ≤300 mGy, but 1000 mGy caused a significant reduction in HR in male pups and growth reduction at 16 weeks of age in both genders. The sham-irradiation protocol included repeated transportation in order to acclimate animals to transport. However, it may have resulted in programming, as sham-irradiation alone resulted in elevated BP measures compared to the offspring of animals that were never transported. Results and conclusions: Overall, there were minimal effects on cardiovascular measures or offspring weight due to irradiation except at 1000 mGy. The presence of maternal stress, a known trigger of developmental programming, may have confounded any potential irradiation effects.

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.

The Surgical Approach Visualization and Navigation (SAVN) System reduces radiation dosage and surgical trauma due to accurate intraoperative guidance

OBJECT

The intraoperative fluoroscopy has been widely used in modern neuro-spinal surgery due to the overwhelming trend toward minimal-access surgery. However, both patients and surgical personnel were under ionizing-radiation exposure during fluoroscopy usage. Since the fluoroscopy constitutes the vast majority of radiation exposure for both surgeons and patients, the development and improvement of new interventional possibilities are of great importance and interests.

PATIENTS AND METHODS

A total of 20 patients were included in the current study, who received thoracic-spinal tumor resection via posterior midline approach. In comparison to the conventional C-Arm mobile fluoroscopy machine, the Surgical Approach Visualization and Navigation (SAVN) System was used to evaluate the effectiveness in reducing radiation.

RESULTS

The pain intensity and Japanese Orthopedic Association Score were equally ameliorated in patients of two groups. However, compared to C-arm group, the SAVN significantly reduced the screening time from 26.8 + 12.4 to 17.1 + 9.2 s (36.2% radiation reduction, P < 0.05), which was mainly due to the significant reduction of radiation attempts (from 12.8 + 4.9 to 7.1 + 5.5 times, P < 0.05). For patients, the direct and scatter radiation dose dropped 30.4% (P < 0.05) in the surgical region and 47.6% (P < 0.01) in the non-surgical region by using the SAVN System. Additionally, the tumor diameter/skin incision ratio increased from 0.39 + 0.4 to 0.47+ 0.28 after SAVN usage. Meanwhile, thedosimeter showed that the radiation dose to the primary surgeon was also lower in the SAVN group (72.1% reduction, P < 0.01).

CONCLUSION

Comparing the conventional C-arm, the SAVN System based thoracic-spinal surgery significantly lowered radiation duration and dosage application towards both surgeons and patients.

Medical Radiation Exposure among Atomic Bomb Survivors: Understanding its Impact on Risk Estimates of Atomic Bomb Radiation

There have been some concerns about the influence of medical X rays in dose-response analysis of atomic bomb radiation on health outcomes. Among atomic bomb survivors in the Life Span Study, the association between atomic bomb radiation dose and exposures to medical X rays was investigated using questionnaire data collected by a mail survey conducted between 2007-2011, soliciting information on the history of computed tomography (CT) scans, gastrointestinal fluoroscopy, angiography and radiotherapy. Among 12,670 participants, 76% received at least one CT scan; 77%, a fluoroscopic examination; 23%, an angiographic examination; and 8%, radiotherapy. Descriptive and multivariable-adjusted analyses showed that medical X rays were administered in greater frequencies among those who were exposed to an atomic bomb radiation dose of 1.0 Gy or higher, compared to those exposed to lower doses. This is possibly explained by a greater frequency in major chronic diseases such as cancer in the ≥1.0 Gy group. The frequency of medical X rays in the groups exposed to 0.005-0.1 Gy or 0.1-1.0 Gy did not differ significantly from those exposed to <0.005 Gy. An analysis of finer dose groups under 1 Gy likewise showed no differences in frequencies of medical X rays. Thus, no evidence of material confounding of atomic bomb effects was found. Among those exposed to atomic bomb doses <1 Gy, doses were not associated with medical radiation exposures. The significant association of doses ≥1 Gy with medical radiation exposures likely produces no substantive bias in radiation effect estimates because diagnostic medical X-ray doses are much lower than the atomic bomb doses. Further information on actual medical X-ray doses and on the validity of self-reports of X-ray procedures would strengthen this conclusion.

CT imaging history for patients presenting to the ED with renal colic--evidence from a multi-hospital database

Background

Patients with renal colic have a 7% chance of annual recurrence. Previous studies evaluating cumulative Abbreviations: computed tomography (CT) exposure for renal colic patients were typically from single centers.

Methods

This was an observational cohort study. Inner-city ED patients with a final diagnosis of renal colic were prospectively identified (1/10/16–10/16/16). Authors conducted structured electronic record reviews from a 6-hospital system encompassing over 192,000 annual ED visits. Categorical data analyzed by chi-square; continuous data by t-tests. Primary outcome measure was the proportion of study group patients with prior history CT abdomen/pelvis CT.

Results

Two hundred thirteen patients in the study group; 59% male, age 38+/− 10 years, 67% Hispanic, 62% prior stone history, flank pain (78%), dysuria (22%), UA (+) blood (75%). 60% (95% CI = 53–66%) of patients received an EDCV CT; hydronephrosis seen in 55% (95% CI = 46–63%), stone in 90%(95% CI = 83–94%). No significant differences observed in the proportion of EDCV patients who received CT with respect to: female vs. male (62% vs. 56%; p = 0.4), mean age (37+/− 9 years vs. 39+/− 11 years; p = 0.2), and Hispanic vs. non-Hispanic white (63% vs.63%; p = 0.96). Patients with a prior stone history were more likely than those with no history to receive an EDCV CT (88% vs. 16%; p < 0.001). 118 (55%; 95% CI = 49–62%) of patients had at least one prior CT, 46 (22%; 95% CI = 16–28%) had ≥3 prior CTs; 29 (14%; 95% CI = 10–19%), ≥ 10 prior CTs. Patients who did not receive an EDCV CT had a significantly higher mean prior number of CTs than those who had EDCV CT (5.1+/− 7.7 vs 2.2+/− 4.9; p < 0.001). Patients with prior stone were more likely to receive only U/S during EDCV (33% vs. 15%; p = 0.003).

Conclusions

Within our EDCV cohort of renal colic patients, 55% had at least one prior CT. The mean number of prior CTs was lower for patients receiving CT on EDCV, and Ultrasound (US) alone was used more often in patients with prior stone history vs. those with no prior history.

Educating about radiation risks in high schools: towards improved public understanding of the complexity of low-dose radiation health effects

The levels of stochastic health effects following exposure to low doses of ionising radiation are not well known. A consequence of the uncertainty is that any radiation exposure is met with deep concern-both by the public and by scientists who disagree about how the partly conflicting results from low-dose studies should be interpreted. The concern is not limited to ionising radiation but is inherent to other areas of modern technologies such as biotechnology or electromagnetic fields. The everyday presence of advanced technologies confronts people with the necessity to take decisions and there is an ongoing debate regarding both the nature and magnitude of potential risks and how education efforts may empower peoples´ decision-making. In the field of radiation research there are different opinions regarding the optimal education methods, spanning from the idea that peoples' fears will be eliminated by introducing dose thresholds below which the risk is assumed to be zero, to suggestions of concentrating research efforts in an attempt to eliminate all uncertainties regarding the effects of low doses. The aim of this paper was to present our approach which is based on developing an education program at the secondary school level where students learn to understand the role of science in society. Teaching about radiation risk as a socio-scientific issue is not based on presenting facts but on showing risks in a broader perspective aiming at developing students' competency in making decisions based on informed assessment. We hope to stimulate and encourage other researchers to pursue similar approaches.

Research Progress on the Biological Effects of Low-Dose Radiation in China

Human are exposed to ionizing radiation from natural and artificial sources, which consequently poses a possible risk to human health. However, accumulating evidence indicates that the biological effects of low-dose radiation (LDR) are different from those of high-dose radiation (HDR). Low-dose radiation–induced hormesis has been extensively observed in different biological systems, including immunological and hematopoietic systems. Adaptive responses in response to LDR that can induce cellular resistance to genotoxic effects from subsequent exposure to HDR have also been described and researched. Bystander effects, another type of biological effect induced by LDR, have been shown to widely occur in many cell types. Furthermore, the influence of LDR-induced biological effects on certain diseases, such as cancer and diabetes, has also attracted the interest of researchers. Many studies have suggested that LDR has the potential antitumor and antidiabetic complications effects. In addition, the researches on whether LDR could induce stochastic effects were also debated. Studies on the biological effects of LDR in China started in 1970s and considerable progress has been made since. In the present article, we provide an overview of the research progress on the biological effects of LDR in China.

Nanozymes: Classification, Catalytic Mechanisms, Activity Regulation, and Applications

Because of the high catalytic activities and substrate specificity, natural enzymes have been widely used in industrial, medical, and biological fields, etc. Although promising, they often suffer from intrinsic shortcomings such as high cost, low operational stability, and difficulties of recycling. To overcome these shortcomings, researchers have been devoted to the exploration of artificial enzyme mimics for a long time. Since the discovery of ferromagnetic nanoparticles with intrinsic horseradish peroxidase-like activity in 2007, a large amount of studies on nanozymes have been constantly emerging in the next decade. Nanozymes are one kind of nanomaterials with enzymatic catalytic properties. Compared with natural enzymes, nanozymes have the advantages such as low cost, high stability and durability, which have been widely used in industrial, medical, and biological fields. A thorough understanding of the possible catalytic mechanisms will contribute to the development of novel and high-efficient nanozymes, and the rational regulations of the activities of nanozymes are of great significance. In this review, we systematically introduce the classification, catalytic mechanism, activity regulation as well as recent research progress of nanozymes in the field of biosensing, environmental protection, and disease treatments, etc. in the past years. We also propose the current challenges of nanozymes as well as their future research focus. We anticipate this review may be of significance for the field to understand the properties of nanozymes and the development of novel nanomaterials with enzyme mimicking activities.

Re-evaluation of the linear no-threshold (LNT) model using new paradigms and modern molecular studies

The linear no-threshold (LNT) model is currently used to estimate low dose radiation (LDR) induced health risks. This model lacks safety thresholds and postulates that health risks caused by ionizing radiation is directly proportional to dose. Therefore even the smallest radiation dose has the potential to cause an increase in cancer risk. Advances in LDR biology and cell molecular techniques demonstrate that the LNT model does not appropriately reflect the biology or the health effects at the low dose range. The main pitfall of the LNT model is due to the extrapolation of mutation and DNA damage studies that were conducted at high radiation doses delivered at a high dose-rate. These studies formed the basis of several outdated paradigms that are either incorrect or do not hold for LDR doses. Thus, the goal of this review is to summarize the modern cellular and molecular literature in LDR biology and provide new paradigms that better represent the biological effects in the low dose range. We demonstrate that LDR activates a variety of cellular defense mechanisms including DNA repair systems, programmed cell death (apoptosis), cell cycle arrest, senescence, adaptive memory, bystander effects, epigenetics, immune stimulation, and tumor suppression. The evidence presented in this review reveals that there are minimal health risks (cancer) with LDR exposure, and that a dose higher than some threshold value is necessary to achieve the harmful effects classically observed with high doses of radiation. Knowledge gained from this review can help the radiation protection community in making informed decisions regarding radiation policy and limits.

Accuracy of photogrammetry for detecting adolescent idiopathic scoliosis progression

BACKGROUND

The gold standard method of monitoring the evolution of scoliosis has been serial standing, posteroanterior, full-length spine radiographs with curvature measurements using the Cobb method. However, over the course of follow-up, patients can receive high radiation doses. Various studies have shown that repeated exposure to radiation in children and adolescents can be harmful to their health.

PURPOSE

To determine the accuracy of photogrammetry in evaluating the progression of adolescent idiopathic scoliosis in comparison with radiography.

STUDY DESIGN

Diagnostic study.

PATIENT SAMPLE

Ninety adolescents subjected to radiographic follow-up of idiopathic scoliosis.

OUTCOME MEASURES

The angle of scoliotic curvature was measured using the Cobb radiographic method and photogrammetry. An increase of 5° or more between two radiographic exams was considered a progression of the curvature and was defined as the standard for calculations of sensitivity, specificity, predictive value, and accuracy of the photogrammetric method for measuring scoliosis progression.

METHODS

Patients were subjected to radiographic and photogrammetric exams concomitantly and were reevaluated after an average of 8.6 months. The exams were analyzed separately and independently by two examiners for progression of scoliosis.

RESULTS

The measurements of the curves at the beginning of the study were 39.5±16.7° and 39.5±14.3° for radiographic and photogrammetric exams, respectively (p=1.0). At the end of the study, the measurements of the curves were 40.2±16.2° and 41.3±15.1° for the radiographic and photogrammetric exams, respectively (p=.310). The photogrammetric method had an accuracy of 89% (Confidence interval [CI] 95%=82.5-95.5) for the detection of scoliosis progression, with a sensitivity of 94.4% (CI 95%=89.6-99.2), a specificity of 86.7% (CI 95%=79.7-93.7), a positive predictive value of 75.5% (CI 95%=66.6-84.4), a negative predictive value of 97.2% (CI 95%=93.8-100), and a Kappa index of 0.75 (CI 95%=66.1-83.9). The interclass correlation coefficient between the two methods was 0.74 (CI 95%=0.65-0.81; p=0).

CONCLUSIONS

The photogrammetric method showed good performance for detecting the progression of adolescent idiopathic scoliosis in comparison with the radiographic exam method.

How to Provide Gadolinium-Free PET/MR Cancer Staging of Children and Young Adults in Less than 1 h: the Stanford Approach

PURPOSE

To provide clinically useful gadolinium-free whole-body cancer staging of children and young adults with integrated positron emission tomography/magnetic resonance (PET/MR) imaging in less than 1 h.

PROCEDURES

In this prospective clinical trial, 20 children and young adults (11-30 years old, 6 male, 14 female) with solid tumors underwent 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) PET/MR on a 3T PET/MR scanner after intravenous injection of ferumoxytol (5 mg Fe/kg) and [¹⁸F]FDG (2-3 MBq/kg). Time needed for patient preparation, PET/MR image acquisition, and data processing was compared before (n = 5) and after (n = 15) time-saving interventions, using a Wilcoxon test. The ferumoxytol-enhanced PET/MR images were compared with clinical standard staging tests regarding radiation exposure and tumor staging results, using Fisher's exact tests.

RESULTS

Tailored workflows significantly reduced scan times from 36 to 24 min for head to mid thigh scans (p < 0.001). These streamlined PET/MR scans were obtained with significantly reduced radiation exposure (mean 3.4 mSv) compared to PET/CT with diagnostic CT (mean 13.1 mSv; p = 0.003). Using the iron supplement ferumoxytol "off label" as an MR contrast agent avoided gadolinium chelate administration. The ferumoxytol-enhanced PET/MR scans provided equal or superior tumor staging results compared to clinical standard tests in 17 out of 20 patients. Compared to PET/CT, PET/MR had comparable detection rates for pulmonary nodules with diameters of equal or greater than 5 mm (94 vs. 100 %), yet detected significantly fewer nodules with diameters of less than 5 mm (20 vs 100 %) (p = 0.03). [¹⁸F]FDG-avid nodules were detected with slightly higher sensitivity on the PET of the PET/MR compared to the PET of the PET/CT (59 vs 49 %).

CONCLUSION

Our streamlined ferumoxytol-enhanced PET/MR protocol provided cancer staging of children and young adults in less than 1 h with equivalent or superior clinical information compared to clinical standard staging tests. The detection of small pulmonary nodules with PET/MR needs to be improved.

Reduced Imaging Radiation Exposure and Costs Associated with Anti-Tumor Necrosis Factor Therapy in Crohn's Disease

BACKGROUND

Radiation exposure from diagnostic imaging may increase cancer risk of Crohn's disease (CD) patients, who are already at increased risk of certain cancers.

AIM

To compare imaging radiation exposure and associated costs in CD patients during the year pre- and post-initiation of anti-tumor necrosis factor (anti-TNF) agents or corticosteroids.

METHODS

Adults were identified from a large US claims database between 1/1/2005 and 12/31/2009 with ≥ 1 abdominal imaging scan and 12 months of enrollment before and after initiating therapy with anti-TNF or corticosteroids. Imaging utilization, radiation exposure, and healthcare costs pre- and post-initiation were examined.

RESULTS

Anti-TNF-treated patients had significantly fewer imaging examinations the year prior to initiation than corticosteroid-treated patients. Cumulative radiation doses before initiation were significantly higher for corticosteroid patients compared to anti-TNF patients (22.3 vs. 17.7 millisieverts, P = 0.0083). After therapy initiation, anti-TNF-treated patients had significantly fewer imaging examinations (2.9 vs. 5.2, P < 0.0001) and less radiation exposure (7.4 vs. 15.4 millisieverts, P <0.0001) than corticosteroid-treated patients in the follow-up period. Reductions in imaging costs adjusted for 1000 patient-years after initiation of therapy were - $275,090 and - $121,960 (P = 0.0359) for anti-TNF versus corticosteroid patients, respectively.

CONCLUSIONS

This analysis demonstrated that patients treated with anti-TNF agents have fewer imaging examinations, less radiation exposure, and lower healthcare costs associated with imaging than patients treated with corticosteroids. These benefits do not account for additional long-term benefits that may be gained from reduced radiation exposure.

Non-uniform radiation-induced biological responses at the tissue level involved in the health risk of environmental radiation: a radiobiological hypothesis

BACKGROUND

The conventional concept of radiation protection is based on epidemiological studies of radiation that support a positive correlation between dose and response. However, there is a remarkable difference in biological responses at the tissue level, depending on whether radiation is delivered as a uniform or non-uniform spatiotemporal distribution due to tissue sparing effects (TSE). From the point of view of radiation micro-dosimetry, environmental radiation is delivered as a non-uniform distribution, and radiation-induced biological responses at the tissue level, such as TSE, would be implicated in individual risk following exposure to environmental radiation.

HYPOTHESIS

We hypothesize that the health risks of non-uniform radiation exposure are lower than the same dose at a uniform exposure, due to TSE following irradiation. Testing the hypothesis requires both radiobiological studies using high-precision microbeams and the epidemiological data of environmental radiation-induced effects. The implications of the hypothesis will lead to more personalized approaches in the field of environmental radiation protection.

CONCLUSION

The detection of spatiotemporal dose distribution could be of scientific importance for more accurate individual risk assessment of exposure to environmental radiation. Further radiobiological studies on non-uniform radiation-induced biological responses at the tissue level are expected.

Evaluation of the physical and biological dosimetry methods in iodine-131-treated patients

The aim of the study was to compare physical and biological dosimetry methods in iodine-131 (I-131)-receiving patients. The present study comprised of 47 patients (mean age: 47.9 ± 15.8 years), treated with I-131. Group I consisted of 17 patients with hyperthyroidism and mean administered activity of this group was 432.9 ± 111 MBq. There were 15 follow-up patients of differentiated thyroid cancer (DTC) in Group II with mean administered activity of 185 ± 22.2 MBq, who were administered scanning dose of I-131. Group III comprised of 15 patients with DTC, ablated with high-dose of I-131, and this group's mean administered activity was 4347.5 ± 695.6 MBq. The whole-body absorbed doses were calculated in all patients both with the Medical Internal Radiation Dosimetry (MIRD) method using MIRDOSE3 software and cytokinesis-block micronucleus (MN) assay-based MN analysis and were compared. The whole-body absorbed dose, calculated by MIRD method, showed very good correlation with the administered I-131 activity (r = 0.89, P < 0.001), but it was moderate in the MN method (r = 0.52, P < 0.01). Absorbed dose estimations with MIRD method were 49.2 ± 20.8 mGy in Group I, 6.5 ± 1.6 mGy in Group II, and 154.3 ± 47.8 mGy in Group III; the differences were statistically significant (P < 0.001), as expected. Pre- and posttreatment MN frequencies differed significantly in all groups (P < 0.05). The whole-body absorbed doses, based on MN method, were 68.2 ± 17.5, 46.0 ± 11.4, and 90.5 ± 26.9 mGy in Groups I–III, respectively. The difference was significant between Group II and Group III (P < 0.01). The mean absorbed dose was 74.6 ± 27.9 mGy with MN versus 68.0 ± 67.1 mGy in MIRD method (P = 0.087) in the entire study population and the correlation was moderate (r = 0.73, P < 0.001). The whole-body absorbed doses, estimated by MN method, showed moderate correlation with administered radioiodine activities in low radioiodine doses and had significantly different and fluctuating values as compared to MIRD method in patients treated with I-131.

Low dose or low dose rate ionizing radiation-induced health effect in the human

The extensive literature review on human epidemiological studies suggests that low dose ionizing radiation (LDIR) (≤100 mSv) or low dose rate ionizing radiation (LDRIR) (<6mSv/H) exposure could induce either negative or positive health effects. These changes may depend on genetic background, age (prenatal day for embryo), sex, nature of radiation exposure, i.e., acute or chronic irradiation, radiation sources (such as atomic bomb attack, fallout from nuclear weapon test, nuclear power plant accidents, ⁶⁰Co-contaminated building, space radiation, high background radiation, medical examinations or procedures) and radionuclide components and human epidemiological experimental designs. Epidemiological and clinical studies show that LDIR or LDRIR exposure may induce cancer, congenital abnormalities, cardiovascular and cerebrovascular diseases, cognitive and other neuropsychiatric disorders, cataracts and other eye and somatic pathology (endocrine, bronchopulmonary, digestive, etc). LDIR or LDRIR exposure may also reduce mutation and cancer mortality rates. So far, the mechanisms of LDIR- or LDRIR -induced health effect are poorly understood. Further extensive studies are still needed to clarify under what circumstances, LDIR or LDRIR exposure may induce positive or negative effects, which may facilitate development of new therapeutic approaches to prevent or treat the radiation-induced human diseases or enhance radiation-induced positive health effect.

Health effects from exposure to dental diagnostic X-ray

The purpose of this review is to summarize the results of studies on of the association between exposure to dental X-rays and health risk. To perform the systematic review, We searched the PUBMED, EMBASE, and MEDLINE databases for papers published before December 15, 2016. A total of 2 158 studies, excluding duplicate studies, were found. Two reviewers independently evaluated the eligibility of each study. The final 21 studies were selected after application of exclusion criteria. In terms of health outcomes, there were 10 studies about brain tumors, 5 about thyroid cancer, 3 about tumors of head and neck areas, and 3 related to systemic health. In brain tumor studies, the association between dental X-ray exposure and meningioma was statistically significant in 5 of the 7 studies. In 4 of the 5 thyroid-related studies, there was a significant correlation with dental diagnostic X-rays. In studies on head and neck areas, tumors included laryngeal, parotid gland, and salivary gland cancers. There was also a statistically significant correlation between full-mouth X-rays and salivary gland cancer, but not parotid gland cancer. Health outcomes such as leukemia, low birth weight, cataracts, and thumb carcinomas were also reported. In a few studies examining health effects related to dental X-ray exposure, possibly increased risks of meningioma and thyroid cancer were suggested. More studies with a large population and prospective design are needed to elaborate these associations further.

Diagnostic concordance between skeletal cephalometrics, radiograph-based soft-tissue cephalometrics, and photograph-based soft-tissue cephalometrics

Objective

This study aims to investigate the diagnostic concordance between skeletal cephalometrics and soft-tissue cephalometrics in identifying facial lower third characteristics.

Materials and methods

We compared a skeletal cephalometric analysis (SCA) to a soft-tissue analysis performed on cephalometric radiographs (rSTCA) and to one performed on profile photograph (pSTCA). Ninety-six pre-treatment digital lateral cephalometric radiographs and 96 digital profile photographs were randomly selected for this study (patients' mean age: 18.33, SD: 3.38, age range: 14-29). Inclusion criteria were as follows: no skeletal asymmetry, well-aligned upper and lower dental arches, no history of orthodontic treatment, prosthodontic treatment, facial surgery and trauma, patient's age between 14 and 30 years, high-resolution images, exams taken with natural head position. Kruskas-Wallis and post hoc pairwise comparisons tests were used to find differences among the considered cephalometric methods. The diagnostic performance of the three methods was also assessed using the receiver-operating characteristic (ROC) curve analysis.

Results

Significant differences were found between SCA and rSTCA and between SCA and pSTCA in defining sagittal and vertical facial lower third characteristics (P < 0.05). No differences were found between rSTCA and pSTCA (P > 0.05) for the same facial characteristics. For each parameters investigated, pSTCA showed an area under the curve much closer to the perfect value of 1.00.

Conclusion

Poor diagnostic concordance was found between SCA and rSTCA and between SCA and pSTCA. pSTCA is a reliable method for evaluating the soft-tissue profile characteristics compared to that performed on cephalograms.

A critical evaluation of the NCRP COMMENTARY 27 endorsement of the linear no-threshold model of radiation effects

Regulatory policy to protect the public and the environment from radiation is universally based on the linear, no-threshold model (LNT) of radiation effects. This model has been controversial since its inception over nine decades ago, and remains so to this day, but it has proved remarkably resistant to challenge from the scientific community. The LNT model has been repeatedly endorsed by expert advisory bodies, and regulatory agencies in turn adopt policies that reflect this advice. Unfortunately, these endorsements rest on a foundation of institutional inertia and numerous logical fallacies. These include most significantly setting the LNT as the null hypothesis, and shifting the burden of proof onto LNT skeptics. Other examples include arbitrary exclusion of alternative hypotheses, ignoring criticisms of the LNT, cherry-picking evidence, and making policy judgements without foundation. This paper presents an evaluation of the National Council on Radiation Protection and Measurements' (NCRP) Commentary 27, which concluded that recent epidemiological studies are compatible with the continued use of the LNT model for radiation protection. While this report will likely provide political cover for regulators' continued reliance on the LNT, it is a missed opportunity to advance the scientific discussion of the effects of low dose, low dose-rate radiation exposure. Due to its Congressionally chartered mission, no organization is better positioned than the NCRP to move this debate forward, and recommendations for doing so in future reviews are provided.

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.

ENVIRONMENTAL IONIZING RADIATION DOSE OUTDOOR IN AN INHABITED AREA WITH A HIGH CONCENTRATION OF URANO-PHOSPHATE IN NORTHEAST OF BRAZIL

A marine phosphorus region with high concentrations of phosphate, coastwise of Pernambuco, Northeast of Brazil, is densely inhabited. Rock phosphate deposits naturally contain uranium ore that produces ionizing radiation from it and its natural descendants, furthermore, its thorium and potassium concentrations are comparable to those usually found in soils. Radiological monitoring of this environment is important to verify the occurrence of harmful effective doses for the adjacent population. This study aimed at the in situ radiometric monitoring in four cities of the north of the Metropolitan Region of Recife-Pernambuco, estimating the effective environmental dose to which the local population is subject. In total, 91 points were monitored with a discriminator-type detector. The outdoor environmental effective dose rates ranged from 1.99 ± 0.09 to 7.59 ± 0.36 mSv y-1, with an average of 2.60 ± 0.69 mSv y-1.

Radiation Exposure in Pediatric Intensive Care Unit Patients: How Much Is Too Much?

We aimed to determine median cumulative radiation exposure in pediatric intensive care unit (PICU) patients, proportion of patients with high radiation exposure (above annual average radiation per person of 6.2 mSv), and determine risk factors for high exposure. This was a retrospective chart review of PICU patients up to 18 years of age admitted to a large community hospital over 2 years. Radiologic studies and radiation exposure were determined for each patient, and total hospital radiation exposure was classified as high (>6.2 mSv) or not (≤6.2 mSv). Median radiation exposure per patient was 0.2 mSv (interquartile range = 2.1) and 11.7% of patients received >6.2 mSv radiation during their hospitalization. Factors associated with high radiation exposure included admission for trauma or surgery, number of computed tomography scans, age, and PICU length of stay (all P < .0001). We concluded that subsets of PICU patients are at risk of high radiation exposure. Policies and protocols may help minimize radiation exposure among PICU patients.

Molecular Signaling in Response to Charged Particle Exposures and its Importance in Particle Therapy

Energetic, charged particles elicit an orchestrated DNA damage response (DDR) during their traversal through healthy tissues and tumors. Complex DNA damage formation, after exposure to high linear energy transfer (LET) charged particles, results in DNA repair foci formation, which begins within seconds. More protein modifications occur after high-LET, compared with low-LET, irradiation. Charged-particle exposure activates several transcription factors that are cytoprotective or cytodestructive, or that upregulate cytokine and chemokine expression, and are involved in bystander signaling. Molecular signaling for a survival or death decision in different tumor types and healthy tissues should be studied as prerequisite for shaping sensitizing and protective strategies. Long-term signaling and gene expression changes were found in various tissues of animals exposed to charged particles, and elucidation of their role in chronic and late effects of charged-particle therapy will help to develop effective preventive measures.