Occupational Radiation Dose Trends in U.S. Radiologic Technologists Assisting with Fluoroscopically Guided Interventional Procedures, 1980-2020.

PURPOSE: To summarize dose trends from 1980 to 2020 for 19,651 U.S. Radiologic Technologists who reported assisting with fluoroscopically guided interventional procedures (FGIPs), overall and by work history characteristics. MATERIALS AND METHODS: A total of 762,310 annual personal dose equivalents at a 10-mm reference depth (doses) during 1980-2020 for 43,823 participants of the U.S. Radiologic Technologists (USRT) cohort who responded to work history questionnaires administered during 2012-2014 were summarized. This population included 19,651 technologists who reported assisting with FGIP (≥1 time per month for ≥12 consecutive months) at any time during the study period. Doses corresponding to assistance with FGIP were estimated in terms of proximity to patients, monthly procedure frequency, and procedure type. Box plots and summary statistics (eg, medians and percentiles) were used to describe annual doses and dose trends. RESULTS: Median annual dose corresponding to assistance with FGIP was 0.65 mSv (interquartile range [IQR], 0.60-1.40 mSv; 95th percentile, 6.80). Higher occupational doses with wider variability were associated with close proximity to patients during assistance with FGIP (median, 1.20 mSv [IQR, 0.60-4.18 mSv]; 95th percentile, 12.66), performing ≥20 FGIPs per month (median, 0.75 mSv [IQR, 0.60-2.40 mSv]; 95th percentile, 9.44), and assisting with high-dose FGIP (median, 0.70 mSv [IQR, 0.60-1.90 mSv]; 95th percentile, 8.30). CONCLUSIONS: Occupational doses corresponding to assistance with FGIP were generally low but varied with exposure frequency, procedure type, and proximity to patients. These results highlight the need for vigilant dose monitoring, radiation safety training, and proper protective equipment.

Characterization and applications of biomacromolecule structurally similar to glycogen as a dispersion aid and skin protection agent.

Glycogen is a naturally occurring or metabolically synthesized biological macromolecule found in a wide range of living organisms, including animals, microorganisms, and even plants. However, naturally sourced glycogen poses challenges for industrial use. This study focused on a biological macromolecule referred to as glycogen-like particles (GLPs), detailing the production methods and biological properties of these particles. In vitro enzymatic production of GLPs was successfully achieved. GLPs synthesized through a simultaneous enzymatic reaction using sucrose had significant changes in their structure and functionality based on the branching enzyme (BE) to amylosucrase (ASase) ratio. As this ratio increased, the GLPs developed higher molecular weights and greater density, solubility, and branching degree while reducing size and turbidity. Structural changes in these enzymes were not observed beyond a critical BE/ASase ratio. Uniformly dispersed curcumin powder was generated in 50 % (w/v) aqueous GLP solution, and the GLPs were non-toxic to human skin keratinocytes at a concentration of 2.5 mg/mL. GLPs with lower branching inhibited tyrosinase activity and melanin synthesis, while those with more long chains displayed effective UV-blocking. By manipulating the BE/ASase ratio, GLPs were shown to display diverse chemical structures and physical characteristics, suggesting their potential application in the food and cosmetics industries.

Absorbed dose coefficients for pediatric differentiated thyroid cancer patients undergoing radioiodine therapy.

The escalating incidence of differentiated thyroid cancer (DTC) in pediatric patients and the resultant growing use of radioactive iodine (RAI) reinforce the need to evaluate radiation exposure to normal tissues and radiation-induced health risks in pediatric patients undergoing RAI therapy. In the current study, we calculated absorbed dose coefficients (i.e. absorbed dose per unit activity administered, mGy MBq-1) specific for pediatric patients with localized DTC undergoing RAI therapy following total thyroidectomy for use in epidemiological studies. We first modified previously-published biokinetic models for adult thyroid cancer patients to achieve a reasonable agreement with iodine biokinetics observed in pediatric patients or design principles addressed in the International Commission on Radiological Protection (ICRP) reference age-specific biokinetic models. We then combined the biokinetic models in conjunction withSvalues derived from ICRP reference pediatric voxel phantoms. The absorbed dose coefficients for pediatric patients were overall greater than those for adults with a ratio (pediatric/adult) up to 11.6 and rapidly decreased with increasing age. The sensitivity analysis showed that the renal clearance rate andSvalues may have the greatest impact on the absorbed dose coefficients with the rank correlation coefficients ranging from -0.53 to -0.82 (negative correlations) and from 0.51 to 0.80 (positive correlations), respectively. The results of the current study may be utilized in clinical or epidemiological studies to estimate organ-specific radiation absorbed doses and radiation-associated health risks among pediatric thyroid cancer patients.

Korean-specific iodine S values for use in internal dosimetry.

The use of iodine S values derived using the International Commission Radiological Protection (ICRP) phantoms may introduce significant bias in internal dosimetry for Koreans due to anatomical variability. In the current study, we produced an extensive dataset of Korean S values for selected five iodine radioisotopes (I-125, I-129, I-131, I-133, and I-134) for use in radiation protection. To calculate S values, we implemented Monte Carlo simulations using the Mesh-type Reference Korean Phantoms (MRKPs), developed in a high-quality/fidelity mesh format. Noticeable differences were observed in S value comparisons between the Korean and ICRP reference phantoms with ratios (Korean/ICRP) widely ranging from 0.16 to 6.2. The majority of S value ratios were lower than the unity in Korean phantoms (interquartile range =0.47-1.28; mean = 0.96; median = 0.69). The S values provided in the current study will be extensively utilized in iodine internal dosimetry for Koreans.

Organ dose reconstruction for the radiation epidemiological study of Korean radiation workers: the first dose evaluation for the Korean Radiation Worker Study (KRWS).

The Korea Institute of Radiological and Medical Sciences has started a radiation epidemiological study, titled "Korean Radiation Worker Study," to evaluate the health effects of occupational exposure to radiation. As a part of this study, we investigated the methodologies and results of reconstructing organ-specific absorbed doses based on personal dose equivalent, Hp(10), reported from 1984 to 2019 for 20,605 Korean radiation workers. For the organ dose reconstruction, representative exposure scenarios (i.e., radiation energy and exposure geometry) were first determined according to occupational groups, and dose coefficients for converting Hp(10) to organ absorbed doses were then appropriately taken based on the exposure scenarios. Individual annual doses and individual cumulative doses were reconstructed for 27 organs, and the highest values were observed in the thyroid doses (on average 0.77 mGy/y and 10.47 mGy, respectively). Mean values of individual cumulative absorbed doses for the red bone marrow, colon, and lungs were 7.83, 8.78, and 8.43 mSv, respectively. Most of the organ doses were maximum for industrial radiographers, followed by nuclear power plant workers, medical workers, and other facility workers. The organ dose database established in this study will be utilized for organ-specific risk estimation in the Korean Radiation Worker Study.

Absorbed dose coefficients for adult thyroid cancer patients undergoing radioiodine therapy.

Use of radioactive iodine (RAI) for thyroid cancer patients is accompanied by elevated risks of radiation-induced adverse effects due to significant radiation exposure of normal tissues or organs other than the thyroid. The health risk estimation for thyroid cancer patients should thus be preceded by estimating normal tissue doses. Although organ dose estimation for a large cohort often relies on absorbed dose coefficients (i.e. absorbed dose per unit activity administered, mGy MBq-1) based on population models, no data are available for thyroid cancer patients. In the current study, we calculated absorbed dose coefficients specific for adult thyroid cancer patients undergoing RAI treatment after recombinant human TSH (rhTSH) administration or thyroid hormone withdrawal (THW). We first adjusted the transfer rates in the biokinetic model previously developed for THW patients for use in rhTSH patients. We then implemented the biokinetic models for thyroid cancer patients coupled withSvalues from the International Commission on Radiological Protection (ICRP) reference voxel phantoms to calculate absorbed dose coefficients. The biokinetic model for rhTSH patients predicted the extrathyroidal iodine decreasing noticeably faster than in the model for THW patients (calculated half-times of 12 and 15 h for rhTSH administration and THW, respectively). All dose coefficients for rhTSH patients were lower than those for THW patients with the ratio (rhTSH administration/THW) ranging from 0.60 to 0.95 (mean = 0.67). The ratio of the absorbed dose coefficients in the current study to the ICRP dose coefficients, which were derived from models for normal subjects, varied widely from 0.21 to 7.19, stressing the importance of using the dose coefficients for thyroid cancer patients. The results of this study will provide medical physicists and dosimetrists with scientific evidence to protect patients from excess exposure or to assess radiation-induced health risks caused by RAI treatment.

Production of branched glucan polymer by a novel thermostable branching enzyme of Bifidobacterium thermophilum via one-pot biosynthesis containing a dual enzyme system.

Glycogen-like particles (GLPs) are applied in food, pharmaceutical, and cosmetics. The large-scale production of GLPs is limited by their complicated multi-step enzymic processes. In this study, GLPs were produced in a one-pot dual-enzyme system using Bifidobacterium thermophilum branching enzyme (BtBE) and Neisseria polysaccharea amylosucrase (NpAS). BtBE showed excellent thermal stability (half-life of 1732.9 h at 50 °C). Substrate concentration was the most influential factor during GLPs production in this system: GLPs yield and [sucrose]ini decreased from 42.4 % to 17.4 % and 0.3 to 1.0 M, respectively. Molecular weight and apparent density of GLPs decreased significantly with increasing [sucrose]ini. Regardless of the [sucrose]ini, the DP 6 of branch chain length was predominantly occupied. GLP digestibility increased with increasing [sucrose]ini, indicating that the degree of GLP hydrolysis may be negatively related to its apparent density. This one-pot biosynthesis of GLPs using a dual-enzyme system could be useful for the development of industrial processes.

Organ dose calculator for diagnostic nuclear medicine patients based on the ICRP reference voxel phantoms and biokinetic models.

The exponential growth in the use of nuclear medicine procedures represents a general radiation safety concern and stresses the need to monitor exposure levels and radiation-related long term health effects in NM patients. In the current study, following our previous work on NCINM version 1 based on the UF/NCI hybrid phantom series, we calculated a comprehensive library of S values using the ICRP reference pediatric and adult voxel phantoms and established a library of biokinetic data from multiple ICRP Publications, which were then implemented into NCINM version 2. We calculated S values in two steps: calculation of specific absorbed fraction (SAF) using a Monte Carlo radiation transport code combined with the twelve ICRP pediatric and adult voxel phantoms for a number of combinations of source and target region pairs; derivation of S values from the SAFs using the ICRP nuclear decay data. We also adjusted the biokinetic data of 105 radiopharmaceuticals from multiple ICRP publications to match the anatomical description of the ICRP voxel phantoms. Finally, we integrated the ICRP phantom-based S values and adjusted biokinetic data into NCINM version 2. The ratios of cross-fire SAFs from NCINM 2 to NCINM 1 for the adult phantoms varied widely from 0.26 to 5.94 (mean = 1.24, IQR = 0.77-1.55) whereas the ratios for the pediatric phantoms ranged from 0.64 to 1.47 (mean = 1.01, IQR = 0.98-1.03). The ratios of absorbed dose coefficients from NCINM 2 over those from ICRP publications widely varied from 0.43 (colon for99mTc-ECD) to 2.57 (active marrow for99mTc-MAG3). NCINM 2.0 should be useful for dosimetrists and medical physicists to more accurately estimate organ doses for various nuclear medicine procedures.

Bias-corrected Hp(10)-to-Organ-Absorbed Dose Conversion Coefficients for the Epidemiological Study of Korean Radiation Workers.

Background: The effects of radiation on the health of radiation workers who are constantly susceptible to occupational exposure must be assessed based on an accurate and reliable reconstruction of organ-absorbed doses that can be calculated using personal dosimeter readings measured as Hp(10) and dose conversion coefficients. However, the data used in dose reconstruction contain significant biases arising from a lack of reality and could result in an inaccurate measure of organ-absorbed doses. Therefore, this study quantified the biases involved in organ dose reconstruction and calculated the bias-corrected Hp(10)-to-organ-absorbed dose coefficients for the use in epidemiological studies of Korean radiation workers. Materials and Methods: Two major biases were considered: (1) the bias in Hp(10) arising from the difference between the dosimeter calibration geometry and the actual exposure geometry and (2) the bias in air kerma-to-Hp(10) conversion coefficients resulting from geometric differences between the human body and slab phantom. The biases were quantified by implementing personal dosimeters on the slab and human phantoms coupled with Monte Carlo method and considered to calculate the bias-corrected Hp(10)-to-organ-absorbed dose conversion coefficients. Results and Discussion: The bias in Hp(10) was significant for large incident angles and low energies (e.g., 0.32 for right lateral at 218 keV), whereas the bias in dose coefficients was significant for the posterior-anterior (PA) geometry only (e.g., 0.79 at 218 keV). The bias-corrected Hp(10)-to-organ-absorbed dose conversion coefficients derived in this study were up to 3.09-fold greater than those from ICRP publications without considering the biases. Conclusion: The obtained results will aid future studies in assessing the health effects of occupational exposure of Korean radiation workers. The bias-corrected dose coefficients of this study can be used to calculate organ doses for Korean radiation workers based personal dose records.

Korean-specific biokinetic model for iodine in radiological protection.

The International Commission on Radiological Protection (ICRP) recently adopted a detailed biokinetic model for systemic iodine with reference transfer coefficients based on typical worldwide dietary intakes of stable iodine. The regional data provided demonstrate that the ICRP reference thyroidal biokinetics may differ substantially across regions with atypically low or high dietary intakes of stable iodine. Importantly, the design of the ICRP model facilitates modifications of reference thyroidal kinetics based on regional dietary iodine intake. The present study extended the ICRP model to the South Korean population, whose dietary iodine intake is much higher than the global mean. The following three transfer coefficients were selected as targets for Korean-specific values: thyroidal uptake rate (λ1), hormonal secretion rate (λ4) and leakage rate of thyroidal organic iodine as inorganic iodide (λ5). The Korean-specific values forλ1,λ4andλ5were determined to be 4.48, 0.0086 and 0.0171 d-1, respectively, to yield the measurements of thyroidal iodine and physiological status of Korean adults. The determinedλ1andλ5values differed noticeably from the ICRP values, whereas theλ4value was comparable to that of the ICRP. Compared with the ICRP reference model, the Korean model, in which the Korean-specific transfer coefficients were adopted, predicted noticeably lower thyroidal uptake and faster decrease of thyroidal iodine. In addition, the predicted cumulative activities of radioiodine in the thyroid were substantially lower (40-80%) than those predicted by the ICRP model. The Korean model developed in this study demonstrates that the iodine biokinetics for Koreans (i.e. a population with a high iodine consumption) obviously differ from the prediction of the ICRP model. Hence, the Korean model may serve to improve the accuracy of thyroid dose estimation for Koreans and will lead to practical changes in matters concerned with radiological protection.

Uncertainty quantification of bioassay functions for the internal dosimetry of radioiodine.

Bioassay functions, which are provided by the International Commission on Radiological Protection, are used to estimate the intake activity of radionuclides; however, they include considerable uncertainties in terms of the internal dosimetry for a particular individual. During a practical internal dose assessment, the uncertainty in the bioassay function is generally not introduced because of the difficulty in quantification. Therefore, to clarify the existence of uncertainty in the bioassay function and provide dosimetrists with an insight into this uncertainty, this study attempted to quantify the uncertainty in the thyroid retention function used for radioiodine exposure. The uncertainty was quantified using a probabilistic estimation of the thyroid retention function through the propagation of the distribution of biokinetic parameters by the Monte Carlo simulation technique. The uncertainties in the thyroid retention function, expressed in terms of the scattering factor, were in the ranges of 1.55-1.60 and 1.40-1.50 for within 24 h and after 24 h, respectively. In addition, the thyroid retention function within 24 h was compared with actual measurement data to confirm the uncertainty due to the use of first-order kinetics in the biokinetic model calculation. Significantly higher thyroid uptakes (by a factor of 1.9) were observed in the actual measurements. This study indicates that consideration of the uncertainty in the thyroid retention function can avoid a significant over- and under-estimation of the internal dose, particularly when a high dose is predicted.

PRACTICAL METHODS FOR INTERNAL DOSE ASSESSMENT FOR RADIOIODINE INTAKE AFTER THYROID BLOCKING: CLASSIFICATION OF DEGREE OF BLOCKAGE AND DETERMINATION OF INSENSITIVE MEASUREMENT POINT.

Iodine thyroid blocking (ITB) suppresses the uptake of iodine to the thyroid and reduces internal doses after radioiodine intake; however, its disturbance of thyroid biokinetics causes considerable uncertainty in the use of dosimetric data intended for assessment of unblocked normal thyroid. To more accurately assess internal dose after ITB, practical dosimetry methods were proposed that consider the ITB effect in a dosimetric manner. A method using the ratio of urine excretion to thyroid retention activity was proposed to retrospectively determine individual-specific ITB levels; bioassay functions and dose coefficients corresponding to ITB levels were calculated separately using the latest biokinetic model and fundamental data. Moreover, insensitive measurement points of time, which led to similar results regardless of ITB level, were determined based on the dose per unit content. Proposed insensitive points for inhalation of vapour forms and particulate forms, respectively, were 1.5 days and 2 days after exposure.

Internal Dose Assessment after 131I-Iodide Misadministration in a Patient With Incompletely Blocked Thyroid Uptake: Personalized Internal Dose Assessment by Estimating Individual-Specific Biokinetics.

In July 2017, a medical accident occurred in South Korea, in which I-iodide solution was misadministered to the wrong patient. Although the International Commission on Radiological Protection provided internal dose coefficients for iodine for blocked thyroid, they were not reliable enough for determining the dose to the patient (whose thyroid uptake was incompletely blocked) due to a discrepancy in biokinetics. Therefore, a personalized dose assessment was performed to derive the individual-specific dose coefficients for the patient. Initially, the thyroid biokinetics of the patient were statistically clarified by fitting bioassay monitoring results and the corresponding predicted bioassay values, which were calculated repeatedly for varying iodine transfer rates in an iodine biokinetic model. After determining the transfer rate for the patient, the individual-specific dose coefficients were then calculated in accordance with latest recommendations of the International Commission on Radiological Protection. According to the individual-specific biokinetics, the 24 h thyroid uptake fraction of iodine was estimated as 0.52%. The thyroid absorbed dose of the patient was evaluated as 21.2 Gy, which differed greatly (by about 9 Gy) from the dose evaluated simply using the reference data for blocked thyroid uptake. The personalized dose assessment carried out for the patient not only reduced considerable uncertainties in the internal dose calculation, but also improved the reliability of the calculated internal dose by adopting the latest dosimetric data, including specific absorbed fraction values based on voxel phantoms. Through the dose assessment of the patient, the methodology of personalized dose assessment considering individual-specific biokinetics was developed.

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 I 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 I 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 I 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 I activity for internal dosimetry.

Health effects of exposure to radon: implications of the radon bed mattress incident in Korea.

Radon is a naturally occurring radioactive material formed by the slow decay of uranium and thorium found in the earth's crust or construction materials. Internal exposure to radon accounts for about half of the natural background radiation dose to which humans are exposed annually. Radon is a carcinogen and is the second leading cause of lung cancer following smoking. An association between radon and lung cancer has been consistently reported in epidemiological studies on mine workers and the general population with indoor radon exposure. However, associations have not been clearly established between radon and other diseases, such as leukemia and thyroid cancer. Radiation doses are assessed by applying specific dose conversion coefficients according to the source (e.g., radon or thoron) and form of exposure (e.g., internal or external). However, regardless of the source or form of exposure, the effects of a given estimated dose on human health are identical, assuming that individuals have the same sensitivity to radiation. Recently, radiation exceeding the annual dose limit of the general population (1 mSv/yr) was detected in bed mattresses produced by D company due to the use of a monazite-based anion powder containing uranium and thorium. This has sparked concerns about the health hazards for mattress users caused by radiation exposure. In light of this event, this study presents scientific information about the assessment of radon and thoron exposure and its human implications for human health, which have emerged as a recent topic of interest and debate in society.

RAPID MONITORING OF INTERNAL CONTAMINATION USING A MOBILE RADIOBIOASSAY LABORATORY FOLLOWING RADIATION EMERGENCIES.

In any radiation emergency, it may be necessary to monitor large numbers of people for internal contamination resulting from inhalation/ingestion of radionuclides released from the accident. The National Radiation Emergency Medical Center of the Korea Institute of Radiological and Medical Sciences constructed a mobile radiobioassay laboratory for rapid field-based monitoring of internal contamination. The main features of the mobile laboratory were designed and the results of performance were tested for rapid monitoring in this paper. We found that maximum throughput for internal contamination monitoring using the whole body counter installed in the laboratory was about 200 people per day. The minimum detectable activities were estimated for the in-vivo and in-vivo radiobioassay systems in the mobile unit. This mobile unit will improve the population monitoring capabilities for internal contamination of individuals affected following nuclear or radiological emergencies.

Internal dosimetry for intake of 18FDG using spot urine sample.

In nuclear medicine, workers handle unsealed radioactive materials. Among the materials, (18)FDG is the most widely used in PET/CT technique. Because of the short half-life of (18)F, it is very challenging to monitor internal exposure of nuclear medicine workers using in vitro bioassay. Thus, the authors developed the new in vitro bioassay methodology for short half-life nuclides. In the methodology, spot urine sample is directly used without normalisation to 1-d urine sample and the spot urinary excretion function was newly proposed. In order to estimate the intake and committed dose for workers dealing (18)FDG, biokinetic models for FDG was also developed. Using the new methodology and biokinetic model, the in vitro bioassay for workers dealing (18)FDG was successfully performed. The authors expect that this methodology will be very useful for internal monitoring of workers who deal short-lived radionuclides in the all field as well as the nuclear medicine field.

Changes of comedonal cytokines and sebum secretion after UV irradiation in acne patients.

The aims of this study were to investigate the effect of UVA and UVB on comedones and sebum secretion in acne patients. Thirteen acne patients were irradiated by UVA (starting from 20J/cm2 and increasing 10% every day) and UVB (starting from 2/3 MED and increasing 10% every day). IL-1alpha, IL-6, IL-1 receptor antagonist (IL-1ra), IL-10 and GM-CSF were measured by ELISA. Measurement of sebum level was also performed. Sebum level was increased in the first three days by UVA (18.4 --> 37.6 microg/cm2) and UVB (19.1 --> 40.0 microg/cm2), but subsequently returned to normal values. Production of IL-1alpha, IL-1ra, IL-6, and IL-10 was generally higher on day 5 than on day 10. GM-CSF was not detected from all comedones. After UV irradiation, clinically stationary acne patients showed a higher increase in cytokine production compared with improved acne patients. It is suggested that IL-10 & IL-1ra have key roles in this cytokine network as the anti-inflammatory comedonal cytokines. They may play important roles in the immuno-regulation, which may be disturbed in stationary acne patients.