The Influence of Magnetic Fields (0.05 T ≤ B ≤ 7 T) on the Response of Personal Thermoluminescent Dosimeters to Ionizing Radiation
 We investigated the main question of whether thermoluminescent dosimeters indicate the correct dose when exposed to magnetic fields from low stray fields up to high magnetic resonance imaging fields inside human magnetic resonance imaging scanners (0.05 T ≤ B ≤ 7 T) during and after irradiation. Medical personnel working in radiology, oncology, or nuclear medicine are regularly monitored with thermoluminescent dosimeters. They might also enter the magnetic field of a magnetic resonance imaging scanner while supervising patients as well as during positron emission tomography-magnetic resonance imaging and magnetic resonance imaging-linac integrated imaging systems and will therefore be exposed to the magnetic fields of magnetic resonance imaging scanners and low stray fields of several millitesla outside of the magnetic resonance imaging scanner, not only before and after, but also during irradiation. Panasonic thermoluminescent dosimetry badges and ring dosimeters for personal monitoring were exposed to magnetic fields originating from a 7 T and a 3 T magnetic resonance imaging scanner as well as neodymium permanent magnets. Four different sealed 137Cs sources were used in two sets of experiments: (1) magnetically induced fading: irradiated thermoluminescent dosimeters (D ≈ 100 mSv) were exposed to a strong magnetic field (B = 7 T) of a human high-field magnetic resonance imaging scanner after irradiation; no magnetically induced fading (magnetoluminescence) for LiBO:Cu or CaSO:Tm was observed; (2) magnetically induced attenuation: thermoluminescent dosimeters were placed during irradiation in a magnetic field for about 60 h; a significantly reduced dose response was observed for LiBO:Cu—interestingly not at maximum B ≈ 7 T but at B ≈ 0.2 T. This experimental observation is possibly relevant especially for medical and technical personnel in nuclear medicine before and during a magnetic resonance imaging scanning procedure. Follow-up studies need to be made to clarify the kinetics of this effect.
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The Influence of Aerosol Density and Shape Factor on the Assessment of Internal Exposure to 239Pu
 Internal exposure due to inhalation of aerosols depends on the ratio of aerodynamic shape factor (χ) to aerosol mass density (ρ). Inhaled aerosol parameters may differ from the default ρ and χ values provided by the International Commission on Radiological Protection, which are adopted for the assessment of internal exposures. This paper focuses on the influences of χ/ρ on the assessment of internal exposure to 239Pu for reference workers. Regional deposition fractions are found to decrease with increasing χ/ρ, and larger decreases are observed with smaller activity median aerodynamic diameter aerosols, while the slow clearance fractions (fs) in the tracheobronchial region are more sensitive for larger activity median aerodynamic diameter aerosols. Results from biokinetics calculations reveal that both the time-dependent content (excretion) and cumulative activities are determined mainly for particles initially deposited in the alveolar-interstitial region, while fs affects the local cumulative activities in the tracheobronchial region. χ/ρ is proven to have different influences for aerosols with different activity median aerodynamic diameters. The default χ/ρ values can be used when activity median aerodynamic diameters are greater than 1 μm, while one should pay attention to the value of χ/ρ when activity median aerodynamic diameters are less than 1 μm, where significant influence may be anticipated.
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The Effects of Radiation and Emitted Light Transport on the Positional Response of 11 cm × 42.5 cm × 5.5 cm NaI(Tl) Detectors
 Experiments were performed with 30 11 cm × 42.5 cm × 5.5 cm NaI(Tl) detectors to better understand their positional response. Spectra were collected using 0.02 to 0.15 MBq point sources of 241Am, 137Cs, 60Co, and 133Ba positioned on lines parallel and perpendicular to the long axis of the crystal along both the narrow and wide detector faces as well as at different distances from them. A greater density of positions was sampled at the ends of the detector, and repeated measurements were made to examine potential gain drifts during the experiment. Spectroscopic peak counts, spectroscopic pulse heights, and net counts were analyzed. Empirical equations were fit to the aforementioned data for each specific source energy as a function of source position. In addition, a Monte Carlo radiation transport code was used to simulate the expected positionally variable response based solely upon radiation absorption. The simulated radiation transport efficiency functions were compared to the experimental data. The effects of the geometric radiation efficiency, the attenuation and scattering of emitted light within the scintillation crystal, and combined effects such as nonuniformity of the photomultiplier tube, photocathode response, and crystal irregularities were then distinguished. Functions describing each effect were derived. The results suggest potential new corrections to data obtained with large scintillation detectors as well as a novel approach to partial positional gamma-ray detection with minimal collimation, given that the energy resolution is within reason for particular photopeaks.
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Enhancements in the Techa River Dosimetry System: TRDS-2016D Code for Reconstruction of Deterministic Estimates of Dose From Environmental Exposures
 Waterborne releases to the Techa River from the Mayak plutonium facility in Russia during 1949–1956 resulted in significant doses to persons living downstream. The dosimetry system Techa River Dosimetry System-2016D has been developed, which provides individual doses of external and internal exposure for the members of the Techa River cohort and other persons who were exposed to releases of radioactive material to the Southern Urals. The results of computation of individual doses absorbed in red bone marrow and extraskeletal tissues for the Techa River cohort members (29,647 persons) are presented, which are based on residence histories on the contaminated Techa River and the East Urals Radioactive Trace, which was formed in 1957 as a result of the Kyshtym Accident. Available 90Sr body-burden measurements and available information on individual household locations have been used for refinement of individual dose estimates. Techa River Dosimetry System-2016D-based dose estimates will be used for verification of risk of low-dose-rate effects of ionizing radiation in the Techa River cohort.
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Counting Efficiencies Determined by Monte Carlo Methods for In Vivo Measurement of 131I Activity in Thyroid
 The counting efficiencies obtained using a physical neck phantom are typically used in the measurement of 131I activity in the thyroid. It is well known, however, that the geometrical discrepancies between the physical neck phantom and the anatomy of the subject can significantly influence the counting efficiencies. Thus, it is necessary to consider the anatomical characteristics of individuals if we need to accurately determine the activity of 131I in the thyroid. This study aims to produce individualized counting efficiencies for thyroid measurement, considering the age, sex, and overlying tissue thickness of the subject being measured by Monte Carlo simulation. Simulations were performed using a series of computational human phantoms of different ages and sexes. The difference in counting efficiencies, depending on the age and sex of the phantom, were found to range from −26 to 3% for the phantoms and monitoring systems considered in the present study. The overlying tissue thickness of the computational phantoms was also modified to find the relationship between the counting ratio of the 80.2 and 364 keV gammas from 131I and the overlying tissue thickness. The equations for estimating the overlying tissue thickness of a subject were then derived from the relationships between counting ratios and overlying tissue thickness. Finally, in the present study, a set of equations representing the variation in counting efficiencies for the 364 keV peak as a function of the overlying tissue thickness were derived, which can be used to determine individualized counting efficiencies for the subject being measured. These individualized counting efficiencies considering the overlying tissue thickness given a subject’s age and sex can provide accurate estimates of 131I activity for internal dosimetry.
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Personal Exposure to Radiofrequency Electromagnetic Fields Among Palestinian Adults
 This work deals with the assessment of personal exposure to radiofrequency electromagnetic fields and the study of temporal and spatial daily variations in a group of 24 adults from the West Bank, Palestine. Exposure was measured using a personal exposure meter EME SPY 140. Mean values of exposure levels from different radiofrequency sources were calculated using both naive and robust regression on order statistics approaches. The total daily exposure from all radiofrequency electromagnetic field sources varied widely among participants depending on their location, the mobile network they use, their activities, and their mode of transportation, ranging from about 0.2 V m−1 to 0.9 V m−1. The average total daily exposure of all participants was about 0.48 V m−1. The main contribution to the mean exposure was from WiFi 2G (45%), GSM900 uplink (19%), GSM900 downlink, and FM radiobroadcasting (each by 11%). Other sources including GSM1800, UMTS2100, WiFi 5G, DECT, TETRA, WiMAX, and TV bands all together contributed 14%. During different activities, participants were exposed to the highest exposure level while traveling and to the lowest exposure while they were sleeping. During the day, participants received the highest exposure during the time period from 1600 to 2400 h. Based on thermal effect of radiofrequency electromagnetic fields, all evaluated personal exposures comply with guidelines recommended for the general public by the International Commission on Non-Ionizing Radiation Protection.
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Thyroid Function in Health Care Workers Exposed to Ionizing Radiation
 Objectives To analyze possible alterations of thyroid function related to dosimetric values in health care workers exposed to ionizing radiation. Materials and Methods Forty-six health care workers exposed to ionizing radiation at a tertiary hospital previously exposed to ionizing radiation were included in the study. Age, sex, history of thyroid diseases, thyroid hormones, work post, service, dosimetric values of previous year, and 5 y period were considered. Alterations of thyroid function and other variables were analyzed by exact logistic regression univariate model. Results 7.1% workers showed an increased serum thyroid-stimulating hormone without free T3 or free T4 alteration. A significant relationship between workers with increased thyroid-stimulating hormone and dosimetric values of previous year (odds ratio 6.35, 95% confidence interval 1.20–98.1, p = 0.021) and previous 5 y period of radiation exposure (odds ratio 1.72, 95% confidence interval 1.12–3.34, p = 0.007) was obtained. Conclusion An increased risk of subclinical hypothyroidism related to radiation doses was observed in this pilot study on a group of health care workers exposed to ionizing radiation.
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Validation Tests of Resuspension Models for a Finite and Infinite Site
 Dose assessment for deposited radionuclides often requires estimates of air concentrations that are derived from measured soil concentrations. For this, dose assessors typically use literature resuspension values that, while empirically based, can vary by orders of magnitude making it difficult to provide accurate dose estimates. Despite the complexities of the physical processes involved in resuspension, the models generally used for dose assessment are relatively simplistic and rarely are the models validated for a specific site, thus making prediction of air concentrations or airborne emissions highly uncertain. Additionally, the size of the contaminated area can have an impact on downwind concentrations, yet literature values do not account for smaller-sized contaminated sites adding additional uncertainty. To test resuspension models for soil-bound radionuclides at finite and infinite spatial scales, measurements of soil and air concentrations are made at (1) a location downwind of a former outfall where 239Pu was released into the environment (a finite site), and (2) uncontaminated locations where regional air sampling provides background measurements of naturally occurring 238U in sampled dust (an infinite site). Measured air concentrations were compared to those predicted using the resuspension factor model and the mass loading model. An area factor was applied to the smaller contaminated site to account for dilution of dust from the contaminated site with dust originating from offsite locations. Results show that when properly parameterized to site conditions, resuspension models can predict air concentrations to within a factor of 10.
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Radiation Monitoring of an Isolation Room for 131I Therapy After the Patients Were Released
 Purpose: This study was performed to obtain a better understanding of the radiation environment in an 131I isolation room after the release of patients with metastasis from thyroid cancer that were treated with 131I doses ranging from 3.7 GBq (100 mCi) to 5.5 GBq (150 mCi) because there have not been any previous studies regarding the ambient radiation levels encountered in 131I isolation rooms after patients are released. Methods: Ambient radiation levels and total and removable surface contamination levels were monitored for 3 weeks after each patient’s release (and before the entry of the next patient). An area located 0.75 m along the corridor outside the room, the door, window, bedside, and the wall of the shower room were monitored with a Nal scintillation survey meter, which was used to obtain readings of the ambient radiation level in six directions, and the mean value for each area was recorded. In addition, areas that were suspected to be highly contaminated, including the toilet bowl, toilet sink, bed head, back of the bed, sink, trash box, and the patient’s pillow, were monitored for total surface contamination with a GM survey meter. Furthermore, the toilet’s U-bend, toilet sink, bed guard, table, shielding, sink plug, and door knob were swabbed for monitoring removable surface contamination, which was measured using a well counter. Conclusion: Ambient radiation monitoring in an 131I isolation room showed that there was negligible risk of harm in terms of the occupational radiation dose level after patients were released. The ambient radiation dose rate was higher near the door because the sink and trash box were located nearby. The toilet bowl, the toilet’s U-bend, and the area around the sink exhibited heavy surface contamination, so these areas require cautious hygiene management.
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The Level of Compliance With the Use of Personal Radiation Monitoring Devices by Qualified Radiographers at Provincial Hospitals in the Tshwane District Area
 When researchers accompanied radiography students during their work integrated learning, it was observed that there is non-compliance with regards the use of personal radiation monitoring devices by radiographers in the Radiology Departments at Provincial hospitals in the Tshwane district area. The aim of this research study was to identify the level of compliance with the use of radiation monitoring devices by radiographers. A quantitative descriptive study method was used, and the data collection tool was questionnaires that were hand delivered to all settings. The sample size of radiographers was 96, and consent was received from 61 participants. The data was collated in a Microsoft Excel® spreadsheet, and the variables were statistically analyzed for frequencies and percentages. The Fisher’s exact test was used for association to answer the level of compliance and management of the radiation monitoring device. Results showed compliance of radiographers in the wearing of radiation monitoring devices but inconsistency as to where the radiation monitoring device should be worn. A lack of awareness about policies from the Radiation Board was also noted.
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