Radiation Exposure Levels Research Articles

Radiological characterization of the phosphate deposit in Al-Jalamid phosphate mining area, Saudi Arabia

Abstract It is a known fact that phosphate rocks have high levels of natural radioactivity due to the presence of large concentrations of radionuclides. This work aims to estimate radiation exposure and dose levels at Al-Jalamid site in northern Saudi Arabia. Al-Jalamid area is one of the largest reserves of phosphate worldwide. Ma’aden, a Saudi Government public company, owns the mine and is responsible for all mining activities. Phosphate and soil samples collected from Al-Jalamid phosphate mining area have been analysed for their uranium and thorium content by an α-spectrometer using radiochemical techniques. The quantity of radon gas was measured both in groundwater and in the atmosphere (indoor and outdoor) at the site using a portable radiation survey instrument. Groundwater samples collected from wells surrounding the mining area were analysed using a liquid scintillation counter in addition to an α-spectrometer. Finally, it is found that phosphate rock concentrate products cannot be utilized economically based on the standards set by the International Atomic Energy Agency (IAEA), since the average activity concentration does not reach the limit set by IAEA and hence are not commercially feasible.

SOLLID - a single centre study to develop methods to investigate the effects of low radiation doses within nuclear medicine, to enable multicentre epidemiological investigations.

There is continuing debate concerning the risks of secondary malignancies from low levels of radiation exposure. The current model used for radiation protection is predicated on the assumption that even very low levels of exposure may entail risk. This has profound implications for medical procedures involving ionising radiation as radiation doses must be carefully monitored, and for diagnostic procedures are minimised as far as possible. This incurs considerable expense. The SOLLID study (ClinicalTrials.gov Identifier: NCT03580161) aims to develop the methodology to enable a large-scale epidemiological investigation of the effect of radiopharmaceutical administrations to patients undergoing diagnostic nuclear medicine procedures. Patients will undergo a series of scans in addition to that acquired as standard of care to enable the radiation doses delivered to healthy organs to be accurately calculated. Detailed analysis will be performed to determine the uncertainty in the radiation dose calculations as a function of the number and type of scans acquired. It is intended that this will inform a subsequent long-term multicentre epidemiological study that would address the question definitively. Secondary aims of the study are to evaluate the range of absorbed doses that are delivered from diagnostic nuclear medicine procedures and to use current risk models to ascertain the relative risks from these administrations.

Assessment of ionizing radiation exposure levels and associated health risk in some selected solid mineral mining sites Edo-North, Nigeria

Ionizing radiation exposure rate and its associated health risks were assessed using Digilert 200 and Rados Radiation Monitoring Meter, integrated with Geographical Positioning System (Garmin GPSMAP 76S) of some selected solid mineral mining sites across Edo-North Nigeria. The mean exposure rates show some characteristic range of 0.010±0.005 𝑚𝑅ℎ𝑟−1 to 0.027 𝑚𝑅ℎ𝑟 −1 across the entire study. The obtained mean exposures rates at all the mining pits were higher than the ICRP standard limit of 0.013 𝑚𝑅ℎ𝑟 −1 , except at freedom limestonesmining pit where we recorded 0.010 mRh-1. It was also observed that limestones mining sites exhibited low exposure rate while granite mining sites exhibited high exposure rate. The computed equivalent dose rate ranges from 1.049 mSvy-1 to 2.287 mSvy-1 , which is well above the recommended permissible limit of 1.0 mSvy-1 for the general public. 91.7% of the mining sites recorded higher absorbed dose rate but the mean AEDE recorded across the entire study area are below the ICRP standard. The average excess lifetime cancer risk shows variation from 0.472 x 10-3 to 1.27 x 10-3 . . By this result, the probability of contacting cancer due to radiation exposure is higher in places like Cinoma pit, Cetraco pit, Niger-Cat pit, Jigom pit, Oaries pit and Petra-Quarries pit.
 Keywords: Assessment, Mining pits, Background, Exposure, lifetime cancer risk

Radiation-induced oral mucositis hamster model using a linear accelerator enhances clinical relevance of preclinical studies for treatment strategy investigation.

Translational animal models for oral mucositis (OM) are necessary to simulate and assess the bioclinical effects and response in humans. These models should simulate high levels of radiation exposure that leads to oxidative stress and inflammatory‐initiated tissue changes. Hamster models have been extensively studied to observe pathological effects of radiation exposure and help in the development of effective treatments. To successfully evaluate the potential for treatment regimens with consistency and relevance, a radiation‐induced OM hamster model was developed using a clinical linear accelerator utilized by cancer patients daily. The dose exposure to the isolated, everted cheek pouch of a hamster, as well as the progression of injury, pro‐inflammatory marker, histological, and elasticity analyses of the buccal pouch were conducted to verify replicability and reproducibility of the injury model. The findings from this model demonstrated its ability to consistently induce injury and resolution over 28 days using an acute dose of 60 Gy. This model was developed to enhance clinical relevance when evaluating potential efficacious treatments and can now be utilized in efficacy studies to better evaluate developed therapeutics in a preclinical model that is easy to translate to clinical studies..

Investigation of potential environmental radiation risks associated with artisanal gold mining in Zamfara State, Nigeria

A total number of 166 average measurements were taken using a handheld radiation meter. The mean terrestrial gamma radiation dose rate (TRD) was 32 nGy h−1 which is less than the world average value of 59 nGy h−1. Kaura Namoda has the highest TRD with a value of 38 nGy h−1, while Bakura has the lowest TRD with a value of 28 nGy h−1. The mean activity concentrations of 226Ra, 232Th and 40 K in soil samples were measured using HPGe and were found to be 18 ± 2 Bq kg−1, 22 ± 3 Bq kg−1 and 251 ± 7 Bq kg−1, respectively. Highest activities of 226Ra, 232Th and 40 K were all found to be in Zurmi local government area with respective values of 31 ± 3 Bq kg−1, 34 ± 3 Bq kg−1 and 419 ± 10 Bq kg−1. The radiological hazards indices associated with the measured activity concentrations were determined as 69 Bq kg−1, 0.2, 0.24, 32 nGyh−1 and 0.05 mSvy−1 for radium equivalent (Raeq), external hazard index (Hex), absorbed dose rate (DR) and annual effective dose (AED), respectively. It can be concluded that despite the illegal mining activities within the area, the radiation exposure level in the area is normal and will not pose any immediate radiation effect to humans and their environs.

Spectral CT quantification stability and accuracy for pediatric patients: A phantom study.

BackgroundSpectral computed tomography (spectral CT) provides access to clinically relevant measures of endogenous and exogenous materials in patients. For pediatric patients, current spectral CT applications include lesion characterization, quantitative vascular imaging, assessments of tumor response to treatment, and more.ObjectiveThe aim of this study is a comprehensive investigation of the accuracy and stability of spectral quantifications from a spectral detector‐based CT system with respect to different patient sizes and radiation dose levels relevant for the pediatric population.Materials and methodsA spectral CT phantom with tissue‐mimicking materials and iodine concentrations relevant for pediatric imaging was scanned on a spectral detector CT system using a standard pediatric abdominal protocol at 100%, 67%, 33% and 10% of the nominal radiation dose level. Different pediatric patient sizes were simulated using supplemental 3D‐printed extension rings. Virtual mono‐energetic, iodine density, effective atomic number, and electron density results were analyzed for stability with respect to radiation dose and patient size.ResultsCompared to conventional CT imaging, a pronounced improvement in the stability of attenuation measurements across patient size was observed when using virtual mono‐energetic images. Iodine densities were within 0.1 mg/ml, effective atomic numbers were within 0.26 atomic numbers and electron density quantifications were within ±1.0% of their respective nominal values. Relative to the nominal dose clinical protocol, differences in attenuation of all tissue‐mimicking materials were maintained below 1.6 HU for a 33% dose reduction, below 2.7 HU for a 67% dose reduction and below 3.7 HU for a 90% dose reduction, for all virtual mono‐energetic energies equal to or greater than 50 keV. Iodine, and effective atomic number quantifications were stable to within 0.1 mg/ml and 0.06 atomic numbers, respectively, across all measured dose levels.ConclusionSpectral CT provides accurate and stable material quantification with respect to radiation dose reduction (up to 90%) and differing pediatric patient size. The observed consistency is an important step towards quantitative pediatric imaging at low radiation exposure levels.

О нормировании радиоактивных выбросов и сбросов промышленных предприятий, не использующих атомную энергию

In accordance with the legislative framework of the system for regulating liquid and airborne discharges of radioactive substances into the environment in force in the Russian Federation, this system is equally designed to regulate discharges of the radionuclides of both artificial and natural origin. The mechanisms of radiological impact of the discharges of natural origin radionuclides on the environment and population do not have any specificity in comparison with the ones of artificial origin radionuclides. Nevertheless, to date, the law enforcement of the Russian system for regulating discharges of the radioactive substances is applied only in relation to the discharges of the radionuclides of artificial origin carried out by nuclear facilities. At the same time, regulation of the discharges of natural origin radionuclides, in accordance with the safety standards of the International Atomic Energy Agency, is the best practice in the field of environmental protection, and the levels of radiation exposure, which characterize such discharges, are not low enough to be neglected. Regulation of the discharges of natural origin radionuclides is provided for in the norms of the European Union and is practically applied in the number of countries of the European Union, where the legislation provides for the regulation of activities, in which the raw materials containing radionuclides of natural origin are used, and the types of economic and other activities subject to this regulation are determined. The Russian system of regulation of discharges of the radioactive substances into the environment is built on the same basic principles and criteria that underlie foreign regulation systems, and which are recommended by the International Atomic Energy Agency. The regulatory and methodological base formed to date in the Russian Federation contains all the required legal mechanisms for the regulation of discharges of the radioactive substances from nuclear facilities, is based on the best international practices and fully complies with the standards of the International Atomic Energy Agency.

Становление атомной промышленности на Урале в аспекте радиационной безопасности

This study examines the formation of the nuclear industry in the Urals from the perspective of radiation safety, identifies objective and subjective factors that led to problems in the field of radiation protection of nuclear facility personnel in the process of developing nuclear production, an assessment of the level and extent of radiation exposure to operating personnel. The author notes that the creation of the domestic nuclear industry took place in extremely difficult conditions of the post-war period and was fraught with many difficulties, especially at the initial stage of the formation of the nuclear industrial complex. During the years of commissioning and development of the first nuclear facilities, first of all, the industry pioneer the Mayak chemical plant, production personnel had to work under conditions of increased radioactive radiation. The experimental nature of plutonium production in the Urals, the novelty of the problem, the miscalculations and mistakes of designers and scientists, the extremely small amount of knowledge about the effects of radiation on a living organism, the secrecy regime and a number of other reasons led to the emergence of an emergency radiation situation at all main production facilities of the chemical plant, which entailed a significant re-irradiation of nuclear facility personnel. However, at that time, the problems of radiation protection of personnel did not have priority for the country's top political leadership. The main thing was to get plutonium for the first Soviet atomic bomb in the shortest possible time, regardless of the cost.

Quantitative positron emission tomography imaging in the presence of iodinated contrast media using electron density quantifications from dual-energy computed tomography.

As preparation for future positron emission tomography (PET)/dual-energy computed tomography (DECT)T imaging modality and new possible clinical applications, the study aimed to evaluate the utility of clinically available spectral results from a DECT system for improving attenuation corrections of PET acquisitions in the presence of iodinated contrast media. The dependence of the accuracy of PET quantification values, reconstructed with conventional and spectral-based attenuation corrections, was examined as a function of the amount of iodine content and x-ray radiation exposure. Measurements were performed on commercial PET/CT and DECT systems, using a semi-anthropomorphic phantom with seven centrifuge tubes in its bore. Five different configurations of tube contents were scanned by both PET/CT and DECT. With the aim of mimicking clinically observed concentrations, in all phantom configurations the center tube contained a high concentration of radionuclide while the peripheral tubes contained a lower concentration of radionuclide. Iodine content was incrementally increased between phantom configurations by replacing iodine-free tubes with tubes that contained the original radionuclide concentration within a 10mg/ml iodine dilution. DECT-based attenuation correction maps were generated by scaling electron density spectral results into corresponding 511keV photon linear attenuation coefficients. Mean SUV values obtained from the nominal PET reconstruction, using conventional CT images as input for the attenuation correction, demonstrate a monotonic increase of 8.6% when the water and radionuclide mixtures were replaced by iodine, water, and radionuclide (same level of activity) mixture. Mean SUV values obtained from the DECT-based reconstruction, in which the attenuation correction utilizes electron density values as input, demonstrate different, more stable behavior across all iodine insert configurations, with a standard deviation to mean ratio of less than 1%. This observed behavior was independent of the area size used for measurement. A minor radiation dose dependency of the electron density values (below 0.5%) was observed. This resulted in consistent (iodine independent) PET quantification behavior, which persisted even at the lowest radiation dose levels tested in our experiment, that is, 25% of the radiation dose utilized for CT acquisition in the clinical PET/CT protocol. Utilization of DECT-generated electron density estimations for attenuation correction benefit PET quantification consistency in the presence of iodine and at nominal and low DECT radiation exposure levels. The ability to correctly account for iodinated contrast media in PET acquisitions will allow the development of new clinical applications that rely on the quantitative capabilities of spectral CT technologies and modern PET systems.

Screening of Lipids for Early Triage and Dose Estimation after Acute Radiation Exposure in Rat Plasma Based on Targeted Lipidomics Analysis.

Rapid early triage and dose estimation is vital for limited medical resource allocation and treatment of a large number of the wounded after radiological accidents. Lipidomics has been utilized to delineate biofluid lipid signatures after irradiation. Here, high-coverage targeted lipidomics was employed to screen radiosensitive lipids after 0, 1, 2, 3, 5, and 8 Gy total body irradiation at 4, 24, and 72 h postirradiation in rat plasma. Ultra-performance liquid chromatography-tandem mass spectrometry with a multiple reaction monitoring method was utilized. In total, 416 individual lipids from 18 major classes were quantified and those biomarkers altered in a dose-dependent manner constituted panel A-panel D. Receiver operator characteristic curve analysis using combined lipids showed good to excellent sensitivity and specificity in triaging different radiation exposure levels (area under curve = 0.814-1.000). The equations for dose estimation were established by stepwise regression analysis for three time points. A novel strategy for radiation early triage and dose estimation was first established and validated using panels of lipids. Our study suggests that it is feasible to acquire quantitative lipid biomarker panels using targeted lipidomics platforms for rapid, high-throughput triage, which can provide further insights in developing lipidomics strategies for radiation biodosimetry in humans.

Assessment of Radiofrequency Radiation Exposure Levels from Mobile Phones and Wireless Hotspots in Some Parts of Makurdi-Nigeria

Radio waves and Microwaves also known as Radio Frequency Radiations (RFR) have been associated with health hazards. This research was carried out to assess the safety level of these radiations in Makurdi, Benue State. Measurement of RFR power density and electric field strength were carried out for mobile phones. A Cornet 15SA Electrosmog meter was used for assessing RFR exposure levels. Measurements of RFR power density (mWm-2) and electric field strength (Vm-1) for wireless hotspots were carried out within 10m radius to offices and open areas with high occupancy. Radiation levels from mobile phones were measured on the surface with mobile phones in contact with the meter in a normal direction such that maximum readings are obtained. A survey questionnaire was also designed to assess the level of knowledge of the residents concerning the effects of exposure to RF radiations. The field strength and Power density from mobile phones were found to range from 0.1946 Vm-1 to 26.2446 Vm-1 and 0.1004 mWm-2 to 1.827 Wm-2 respectively. These are within ICNIRP recommended value of 10 Wm-2 for members of the public. Environmental levels of RFR in areas with RFR generating devices showed that RFR levels ranged from 5.0595Vm-1 (0.0679 Wm-1) to 7.3961Vm-1 (0.145 Wm1). Also, assessment of areas with Wi-Fi hotspots showed that the presence of hotspots significantly increased background levels of RFR. These values were compared with measurements carried out in areas without RF devices which ranged from 0.10212Vm-1 (0.02766 mWm-2) to 1.7334 Vm-1 (0.0079 Wm-2). The presence of devices was seen to increase the amount of radiation in the environment. The questionnaire results indicated that there was need to further educate the public on the effects of these radiations and precautionary to be adopted for safety.

Assessment of radiation dose level in farm soils of mission quarters, Wukari, Taraba State, Nigerian

The study has assessed the amount of radiation exposed to farm soils in mission quarters Wukari, Taraba State. Assessment of radiation dose level is very important, especially in soil since man depends on Soil for his food. Assessment of radiation will help to know the radiation dose in the soil. The objective of this work is to determine radiation dose in soils and to provide necessary information of human health risks associated with radioactivity in soil and its effects on plant materials as well as human being. Different soil samples were collected and the Radiation Alert Inspector EXP, was used to measure the level of radiation exposure in the soil samples. The results showed low amount of radiation dose level. The average dose values ranging between 0.035±0.097 to 0.333±0.289, an absorbed dose rate ranging between 3.50 x 10-8±0.097 to 3.33 x 10-7±0.289 and annual dose rate ranging between 0.059±0.097 to 0.758±0.289. These results revealed that the dose rates do not exceed the recommended values by International Commission on Radiological Protection (ICRP) is 1mSvyr1 for the general public. It is less and in compliance with the recommended radiation dose level. Therefore do not pose a significant health hazard. The radiation dose level has no negative effect on both the plants and the dwellers. Therefore the study area is safe for human activities.

Radon concentration and radiation exposure levels in workplace buildings of downtown Rio de Janeiro City, SE, Brazil

Radon, a noble radioactive gas, can reach levels that pose a risk to public health in poorly ventilated environments such as residences and buildings. It is a known carcinogenic agent, responsible for the incidence of about 14% of lung cancer in the world. In this work an evaluation of indoor radon, that downtown Rio de Janeiro workers are exposed in working daily life was carried out using an alpha detector (RAD7). The indoor radon concentration and effective dose are below the limits recommended by international standards.

Novel electromagnetic-based navigation for percutaneous transforaminal endoscopic lumbar decompression in patients with lumbar spinal stenosis reduces radiation exposure and enhances surgical efficiency compared to fluoroscopy: a randomized controlled trial.

BackgroundPercutaneous transforaminal endoscopic lumbar decompression (PTELD) is an emerging surgical alternative for treating lumbar spinal stenosis (LSS). However, the foraminoplasty procedure often requires repeated fluoroscopy, and endoscopy just offers a local view. No studies have focused on decreasing radiation exposure with electromagnetic navigation assistance. This study introduces a novel electromagnetic-based navigation (EMN) endoscopic system for PTELD in patients with LSS and compares the results in navigation and fluoroscopy groups.MethodsEighty-eight patients with LSS were randomized into either a navigation (44 patients) or fluoroscopy group. Duration of surgery, cannula placement time, radiation dose, blood loss, intraoperative pain assessment, and postoperative hospitalization stay were evaluated. The clinical outcomes were evaluated using a visual analogue scale (VAS), the Oswestry Disability Index (ODI), 6-minute walk test, and modified Macnab criteria.ResultsEighty-five patients were followed-up for at least 12 months. The duration of surgery and cannula placement time were significantly more efficient in the navigation group (P=0.03 and P<0.001). Intraoperative pain assessment showed significantly less pain in the navigation group (P=0.038). The radiation dose was significantly higher in the fluoroscopy group than the navigation group (P<0.001). The VAS scores for back (P<0.001) and leg (P<0.001) pain improved significantly in both groups after surgery, as did the ODI (P<0.001) scores. Improvements in walking ability and Macnab criteria assessments at the 12-month follow-up, assessed subjective by patient assessments did not differ between the two groups.ConclusionsThe EMN system used in PTELD for patients with LSS compared to fluoroscopy enhances efficiency for foraminoplasty, reduces intraoperative pain and levels of radiation exposure. It results in outcomes comparable with results using fluoroscopy.

UV RADIATION AND NEUROTICISM

Decreased UV radiation is associated with augmented depression, drug use, and domestic violence. Findings entailing folic acid suggest that gender moderates such relationships. The present study was designed to evaluate the relationship between UV radiation and Neuroticism among females and males. Representative consumer panels of three Peruvian cities at decreasing levels of radiation exposure were compared. A 7-item Neuroticism scale was used. A hierarchical regression model revealed that Neuroticism increases with decreased exposure to UV radiation, but the expected radiation x gender interaction failed to materialize. The findings uphold the concept that Neuroticism is responsive to geophysical stimulation. Improvements of mental health can be expected with climate change. The study should be replicated with strengthened methodology.

Lifetime cancer risks from occupational radiation exposure among workers at interventional radiology departments.

Interventional medical radiation workers represent an under-studied population worldwide, although they receive relatively high occupational radiation doses. This study aimed to estimate the lifetime cancer risk from occupational radiation exposure among workers at interventional radiology departments. A field survey of interventional medical workers in nationwide branches of the Korean Society of Interventional Radiology was conducted in 2017. Organ-specific radiation doses were estimated using national dose registry data and conversion coefficients provided by the International Commission on Radiological Protection. Lifetime attributable risk (LAR) and lifetime fractional risk (LFR) were calculated based on realistic exposure scenarios using a radiation risk assessment tool. LARs from occupational radiation exposure until the age of retirement for all cancers combined were 338 (90.3-796.1), 121 (33.5-288.7), and 156 (41.1-390.6) per 100,000 individuals for male radiologists, male radiologic technologists, and female nurses, respectively. LFR for all cancers combined ranged from 0.22% (0.06-0.53) to 0.63% (0.17-1.47). Regarding the organ site, the highest LAR and LFR among all groups were observed for thyroid cancer. This study provides timely evidence of potential cancer burden from the current levels of occupational radiation exposure among workers at interventional radiology departments. The risks varied by occupational groups, and workers, particularly interventional radiologists, need to be carefully monitored for radiation.

The Grand SANS FLUORO (SAy No Series to FLUOROsopy) Study: Examining Fluoroscopy Use in More than 1,000 Ablation Procedures.

The majority of electrophysiologists routinely use fluoroscopy (FLUORO) during ablation procedures for common arrhythmias despite the known complications of radiation exposure and protective lead use. This study assessed the safety of catheter ablation (CA) with FLUORO versus without FLUORO (SANS FLUORO) in patients with the following common arrhythmias: atrial fibrillation (AF), atrial flutter, supraventricular tachycardia, and ventricular tachycardia. A total of 1,258 CA procedures were performed in 816 consecutive patients over a 53-month period (SANS FLUORO CA: 609 patients; FLUORO CA: 209 patients). The secondary outcome was the efficacy of AF ablation in FLUORO versus SANS FLUORO patients. Ultimately, there was no statistically significant difference found concerning the safety of CA in the SANS FLUORO and FLUORO groups in terms of procedure time, vascular complications, tamponade, stroke, or death. FLUORO patients had markedly increased FLUORO time, increased radiation exposure, and increased dose-area product (all p < 0.0001). AF development after SANS FLUORO CA of AF was not different from that after FLUORO CA regardless of the pulmonary vein isolation (PVI) modality used (cryoablation versus radiofrequency) at 24 months (p = 0.21). Additionally, women fared just as well as men after CA ablation for AF. At 36 months, 58% of SANS FLUORO AF device patients were free from AF. As such, SANS FLUORO CA of common arrhythmias appears to be as safe as FLUORO CA but with a markedly reduced level of radiation exposure. Also, SANS FLUORO CA remains as effective as FLUORO CA in the prevention of AF for up to 24 months.

Should Radiation Exposure be an Issue of Concern in Children With Multiple Trauma?

The aims of this study were 3-fold: first, establish the level of radiation exposure experienced by the pediatric trauma patients; second, model the level of risk of developing fatal carcinogenesis; and third, test whether pattern of injury was predictive of the level of exposure. There are certain conditions that cause children to be exposed to increased radiation, that is, scoliosis, where level of radiation exposure is known. The extent that children are exposed to radiation in the context of multiple traumas remains unclear. Patients below the age of 16 years and with an Injury Severity Score (ISS) ≥10, treated by a Major Trauma Center for the period January 2008 to December 2018 were identified. The following data were extracted for the year following the patient's injury: number, doses, and type of radiological examination.The sex and age of the patient was taken into account in the calculation of the risk of developing a carcinogenesis. The median radiation dose of the 425 patients identified in the 12 months following injury, through both CT and radiographs, was 24.3 mSv. Modeling the predictive value of pattern of injury and other relevant clinical values, ISS was proportionately predictive of cumulative dose received. A proportion of younger polytrauma patients were exposed to high levels of radiation that in turn mean an increased risk of carcinogenesis. However, the ISS, age, injury pattern, and length of hospital stay are predictive of both risks, enabling monitoring and patient advisement of the risks.

Assessment of Suspected Malignancy or Infection in Immunocompromised Patients After Solid Organ Transplantation by [18F]FDG PET/CT and [18F]FDG PET/MRI.

To study the value of 2-deoxy-2-[18F]fluoro-D-glucose([18F]FDG) positron emission tomography/computed tomography (PET/CT) and [18F]FDG positron emission tomography/magnetic resonance imaging (PET/MRI) in assessing immunocompromised patients with suspected malignancy or infection. [18F]FDG-PET/CT and [18F]FDG-PET/MRI examinations of patients who were immunocompromised after receiving lung, heart, pancreas, kidney, liver, or combined kidney-liver transplants were analyzed in this retrospective study. Patients underwent whole-body hybrid-imaging because of clinical signs of malignancy and/or infection. Findings were assessed by molecular features ([18F]FDG-uptake) and morphological changes. The final diagnosis, which was arrived at after review of clinical, laboratory, and histopathologic analyses and follow-up imaging studies, served as the reference standard. Altogether, (i) 28 contrast-enhanced [18F]FDG-PET/CT scans (CE-PET/CT), (ii) 33 non-contrast [18F]FDG-PET/CT scans (NC-PET/CT), and (iii) 18 [18F]FDG-PET/MRI scans were included. Additionally, 12/62 patients underwent follow-up PET imaging to rule out vital tumor or metabolic active inflammatory processes. CE-PET/CT exhibited 94.4% sensitivity, 80.0% specificity, 89.5% positive predictive value (PPV), 88.9% negative predictive value (NPV), and 89.3% accuracy with regard to the reference standard. NC-PET/CT exhibited 91.3% sensitivity, 80.0% specificity, 91.3% PPV, 80.0% NPV, and 87.9% accuracy. PET/MRI exhibited 88.6% sensitivity, 99.2% specificity, 99.6% PPV, 81.3% NPV, and 94.4% accuracy. Exact McNemar statistical test (one-sided) showed significant difference between the CT-/MR-component alone and the integrated PET/CT and PET/MRI for diagnosis of malignancy or infection (p value < 0.001). Radiation exposure was 4- to 7-fold higher with PET/CT than with PET/MRI. For immunocompromised patients with clinically unresolved symptoms, to rule out vital tumor manifestations or metabolic active inflammation, [18F]FDG-PET/MRI, CE-[18F]FDG-PET/CT, and NC-[18F]FDG-PET/CT exhibit excellent performance in diagnosing malignancy or infection. The main strength of PET/MRI is its considerably lower level of radiation exposure than that associated with PET/CT.

Outcome Assessment in Epidemiological Studies of Low-Dose Radiation Exposure and Cancer Risks: Sources, Level of Ascertainment, and Misclassification.

Outcome assessment problems and errors that could lead to biased risk estimates in low-dose radiation epidemiological studies of cancer risks have not been systematically evaluated. Incidence or mortality risks for all cancers or all solid cancers combined and for leukemia were examined in 26 studies published in 2006-2017 involving low-dose (mean dose ≤100 mGy) radiation from environmental, medical, or occupational sources. We evaluated the impact of loss to follow-up, under- or overascertainment, outcome misclassification, and changing classifications occurring similarly or differentially across radiation dose levels. Loss to follow-up was not reported in 62% of studies, but when reported it was generally small. Only one study critically evaluated the completeness of the sources of vital status. Underascertainment of cancers ("false negatives") was a potential shortcoming for cohorts that could not be linked with high-quality population-based registries, particularly during early years of exposure in five studies, in two lacking complete residential history, and in one with substantial emigration. False positives may have occurred as a result of cancer ascertainment from self- or next-of-kin report in three studies or from enhanced medical surveillance of exposed patients that could lead to detection bias (eg, reporting precancer lesions as physician-diagnosed cancer) in one study. Most pediatric but few adult leukemia studies used expert hematopathology review or current classifications. Only a few studies recoded solid cancers to the latest International Classification of Diseases or International Classification of Diseases for Oncology codes. These outcome assessment shortcomings were generally nondifferential in relation to radiation exposure level except possibly in four studies. The majority of studies lacked information to enable comprehensive evaluation of all major sources of outcome assessment errors, although reported data suggested that the outcome assessment limitations generally had little effect on risk or biased estimates towards the null except possibly in four studies.