Health Phys. Abstracts，Volume 120,Number 3

RadiationExposureDoseDistributionofWorkersEngagedinDecontaminationandRelatedWorkFollowingtheFukushimaNuclearDisaster

Hisanori Fukunaga1,2, Tsubasa Ogawa3, Tomohiro Asano3, Atsuo Ito3

(1.Shonan Kamakura General Hospital Affiliated Clinical Research Center, 1370-1 Okamoto, Kamakura, Kanagawa 247-8533, Japan;2.Tohoku Medical Megabank Organization, Tohoku University, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8573, Japan;3.Radiation Dose Registration Center, Radiation Effects Association, 1-9-16 Kaji-cho, Chiyoda-ku, Tokyo 101-0044, Japan)

Abstract:Since the Fukushima nuclear disaster in March 2011, decontamination operations have been conducted across a wide area of Japan.The Japanese System of Registration and Management of Radiation Exposure Doses for Decontamination and Related Work, which was launched in November 2013, is administered by the Radiation Effects Association with the participation of prime contractors who perform decontamination and related work.This study aims to investigate the radiation exposure dose distribution of workers engaged in decontamination and related work, using data obtained from the above registration system.We analyzed the radiation exposure dose distributions among workers in 11 Fukushima prefectural municipalities(Futaba, Iitate, Katsurao, Kawamata, Kawauchi, Namie, Naraha, Minamisōma, Okuma, Tamura, and Tomioka)from 2013 to 2018.The mean radiation exposure doses of workers in each municipality were generally low, although a Kruskal-Wallis test showed a significant regional difference in the figures.The highest mean dose was 0.5 mSv in Okuma in 2018, and the second highest was that of Futaba.The workers engaged in the land development and construction of the interim facilities may have been exposed to more radiation than other workers across 11 Fukushima prefectural municipalities.Following large-scale nuclear accidents or radiation emergencies, radiation dose monitoring and health management for each worker need to be optimized according to their work assignments.

Keywords: accidents, power reactor; decontamination; emergencies, radiological; occupational safety

Health Phys.120(3):251-257; 2021

Long-termRetentionofPlutoniumintheRespiratoryTractsofTwoAcutely-exposedWorkers:EstimationofBoundFraction

Deepesh Poudel1, Maia Avtandilashvili2, Luiz Bertelli1, John A.Klumpp1, Sergei Y.Tolmachev2

(1.Radiation Protection Division, Los Alamos National Laboratory, Los Alamos, NM;2.US Transuranium and Uranium Registries, Washington State University, Richland, WA)

Abstract:Inhalation of plutonium is a significant contributor of occupational doses in plutonium production, nuclear fuel reprocessing, and cleanup operations.Accurate assessment of the residence time of plutonium in the lungs is important to properly characterize dose and, consequently, the risk from inhalation of plutonium aerosols.This paper discusses the long-term retention of plutonium in different parts of the respiratory tract of two workers who donated their bodies to the US Transuranium and Uranium Registries.The post-mortem tissue radiochemical analysis results, along with the urine bioassay data, were interpreted using Markov Chain Monte Carlo and the latest biokinetic models presented in the Occupational Intakes of Radionuclides series of ICRP publications.The materials inhaled by both workers were found to have solubility between that of plutonium nitrates and oxides.The long-term solubility was also confirmed by comparison of the activity concentration in the lungs and the thoracic lymph nodes.The data from the two individuals can be explained by assuming a bound fraction(fraction of plutonium deposited in the respiratory tract that becomes bound to lung tissue after dissolution)of 1% and 4%, respectively, without having to significantly alter the particle clearance parameters.Effects of different assumptions about the bound fraction on radiation doses to different target regions was also investigated.For inhalation of soluble materials, an assumption offbof 1%, compared to the ICRP default of 0.2%, increases the dose to the most sensitive target region of the respiratory tract by 258% and that to the total lung by 116%.Some possible alternate methods of explaining higher-than-expected long-term retention of plutonium in the upper respiratory tract of these individuals—such as physical sequestration of material into the scar tissues and possible uptake by lungs—are also briefly discussed.

Keywords:239Pu; dosimetry, internal; health effects; intake, radionuclide

Health Phys.120(3):258-270; 2021

InternalRadiationDoseEvaluationforanUnrupturedPostReleaseTristructuralIstropicFuelParticleforAdvancedandMicro-reactorApplications

Caitlin A.Condon, Pavlo Ivanusa, Amoret L.Bunn, Philip J.Jensen1

(1.Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O.Box 999, MSIN K7-68, Richland, WA 99352)

Abstract:There are unique benefits from advanced/micro-reactor designs and fuel types that offer safety features in the case of an accident that may reduce environmental consequences compared to conventional reactors and fuels.Tristructural isotropic(TRISO)fuel particles are a robust advanced nuclear fuel type that leads to the unique question of how unruptured, activated TRISO particles will interact with humans.TRISO particles are 900 μm in size, and that particle size restricts internal dose assessment to the ingestion pathway.Activity of the TRISO particle was established by High Temperature Engineering Test Reactor simulations.The TRISO particle encapsulation was assumed to be perfect; exploration of internal dose contribution from radionuclides released from encapsulation was not included.The TRISO particle was assumed to be mixed actively within each alimentary tract compartment such that homogenous distribution could be assumed according to the International Commission on Radiological Protection publication 133.The dose assessment results indicate that the rectosigmoid colon had the highest internal organ dose for both reference male(2.1 Sv)and female(2.3 Sv).The internal dose from ingestion of the scenario-specific TRISO particle was 0.25 Sv for the reference male and 0.29 Sv for the reference female, which exceeds the annual occupational effective dose limit of 0.05 Sv in the Code of Federal Regulations, 10 CFR Part 20 Subpart C.Similarly, the annual occupational limit of 0.5 Sv to any one organ would be exceeded for the left colon, right colon, and rectosigmoid colon for both the reference male and female.

Keywords: contamination, environmental; dose, internal; nuclear reactor; reference man

Health Phys.120(3):271-277; 2021

EstimationofHeightsandBodyMassesofTuberculosisPatientsintheCanadianFluoroscopyCohortStudyforUseinIndividualDosimetry

Kathleen M.Thiessen1, A.Iulian Apostoaei1, Lydia B.Zablotska2

(1.Oak Ridge Center for Risk Analysis, Inc., Oak Ridge, TN;2.Department of Epidemiology and Biostatistics, School of Medicine, University of California-San Francisco, San Francisco, CA)

Abstract:This paper documents the estimation of mean heights and body masses, by age and sex, used in development of organ-specific dose conversion coefficients for external radiation for a historical cohort of about 64,000 patients from the Canadian Fluoroscopy Cohort Study.Patients were exposed to repeated fluoroscopy and chest radiography examinations in the course of treatment for tuberculosis in residential medical facilities throughout Canada between 1930 and 1969.Using Canadian national survey data and extensive literature review, mean heights and masses were obtained for the White population of Canada during the time period of interest, and the differences in mean body mass between tuberculosis patients and the general population were estimated.Results in terms of mean height and body mass of Canadian tuberculosis patients, with uncertainties, are reported for selected age groups(children of ages 1, 5, 10, and 15 y and adults age 20+)and for both sexes.Use of estimated average heights and body masses by age and sex permits the adjustment of computerized phantoms for body mass for a given age, thereby increasing the relevance of the organ-specific dose conversion coefficients for the cohort and improving the accuracy of the resulting estimated organ doses.

Keywords: dosimetry, external; epidemiology; fluoroscopy; health effects

Health Phys.120(3):278-287; 2021

EvaluationofOrganDosesforPediatricComputedTomographyUsingaNewlyDesignedRadiophotoluminescenceGlassDosimeterandComparisonwithaMonteCarloSimulation-basedDoseCalculator

Weishan Chang, Yusuke Koba1

(1.Center for Radiation Protection Knowledge, National Institute of Radiological Sciences, QST, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555, Japan)

Abstract:Management of patient dose is an effective way to help optimize computed tomography(CT)scanning conditions and CT dose.Organ dose is one of the preferred quantities for radiation protection because of its correlation with radiation risk.To date, the WAZA-ARI dose calculator is the only freely available CT dose calculator also applicable for pediatric patients.However, no reports of its evaluation have appeared since the latest version of WAZA-ARI was released.In this study, to evaluate the latest version of WAZA-ARI, we measured the organ dose in a 5-y-old anthropomorphic phantom by a newly developed radiophotoluminescence glass dosimeter(RGD)dosimetry system and compared these results with the calculation results from WAZA-ARI.The newly designed RGDs have less angular dependence because of the additional filter.RGDs were individually calibrated with the ISOVOLT TITAN-320 X-ray generator.All the experimental measurements for this study were performed using a CT scanner.To consider the difference of CT output between the nominal and actual machine, the measuredCTDIairwas used to correct the calculation results obtained from WAZA-ARI.After the corrections using the measuredCTDIair, the calculation results from WAZA-ARI were relatively lower than the measured results with a range of 8%-20%, which corresponds to the dose difference caused by the difference in effective diameter.In conclusion, the calculation accuracy of WAZA-ARI is guaranteed when the normalization factor specific to each CT scanner(CTDIair)and the shape of the phantom are taken into consideration.

Keywords: computed tomography; dose, organ; dosimetry; health effects

Health Phys.120(3):288-295; 2021

AHistoryoftheRadiationWarningSign

Paul W.Frame1, Emily A.Frame2

1.104 Weldon Lane, Oak Ridge, TN 37830;2.Department of Nuclear Engineering, University of California, Berkeley, CA 94720-1777)

Abstract:This paper provides a history of the radiation warning sign with a focus on the period from 1946 to 1948.It employs previously unpublished material from the University of California Radiation Laboratory’s Health Chemistry Group, the memoirs of John Gifford, and an account by George Warlick.Also considered is an alternative version of the sign’s origin described by Cyrill Orly.

Keywords: education, health physics; historical profiles; radiation, ionizing; radiation protection

Health Phys.120(3):296-300; 2021

InvestigationintotheEnergyandScatterResponseofOSLDsatDiagnosticEnergiesUsingaC-armSystem

Kevin Liu1

(1.Kevin Liu, Columbia University, 500 W 120th St, New York, NY)

Abstract:Optically stimulated luminescent dosimeters(OSLDs)are radiation detectors commonly used in a clinical setting to monitor the dose to patients undergoing imaging or interventional procedures, especially those involving fluoroscopy.In dose tracking using OSLDs, it is important to consider that photons at the diagnostic energy range are prone to energy spectrum shifts from scattering interactions in the medium and that OSLDs have been reported to yield a somewhat strong energy-dependent response in the diagnostic energy range.This study examines the response of OSLDs exposed to a spectrum of photons in the diagnostic energy range(60-120 kVp), both free-in-air and on the surface of a PMMA phantom, within and just outside of the exposure field.From these measurements, it was observed that the response differs substantially(as high as 30%)in OSLDs irradiated under identical exposure settings but with differences in beam quality and scattering conditions.Furthermore, this study devises a method of weighted averages to calculate the calibration factors for OSLDs exposed to both primary and scatter photons, which were approximately 2%-5% less than their corresponding measured values.This study emphasizes the need to develop different calibration factors in the clinical use of OSLDs for diagnostic imaging procedures, especially for procedures in which more precise dose measurements may be necessary.

Keywords: calibration; dosimetry, calibration; fluoroscopy; medical radiation

Health Phys.120(3):301-307; 2021

TrendsinProfessionalRadiationExposuresofMedicalStaffCoveredbyPersonalDoseMonitoringataRijekaClinicalHospitalCentre(2000to2015)

Abstract:The increase in the number of radiological procedures observed in recent years also means greater exposure to ionizing radiation for the medical staff performing these procedures.This is most pronounced in the teams that perform interventional and invasive radiological procedures.The aim of this study was to examine the impact of increasing numbers of radiological procedures on the effective dose received by medical staff and to determine which professions received the highest exposure to ionizing radiation.Data for effective doses of 326 employees of Rijeka Clinical Hospital Centre covered by personal dosimetry in the period from 2000 to 2015 have been analyzed.Employees were divided by sex, by departments in which they were employed, and according to their professions.The analysis has shown that the exposure level of workers working in the ionizing radiation zone is typically well below the dose limits.During 2015, most employees(over 96.3%)received an annual effective dose of less than 0.1 mSv.Only three persons received an annual dose higher than 0.5 mSv, and one person received an annual dose of 6.9 mSv.Comparison of the radiation exposure doses of medical workers of different professions has shown that the highest dose of radiation is received by cardiologists involved in interventional cardiology procedures.Therefore, the additional need is to take care of their protection, check the manner of their work, and ensure more even workload of cardiologists participating in procedures that involve higher exposure to ionizing radiation.

Keywords: collective dose; effective dose; occupational safety; radiation protection

Health Phys.120(3):308-315; 2021

LeastSignificantChangesandReproducibilityof131IUptakeTest

(1.Hatay Mustafa Kemal University, Kirikan Vocational School, Hatay, Turkey;2.Health Sciences University, Ankara Diskapi Yildirim Beyazit Training and Research Hospital, Ankara, Turkey)

Keywords:131I; medical radiation; nuclear medicine; thyroid

Health Phys.120(3):316-320; 2021

RadiationMappingforanUnmannedAerialVehicle:DevelopmentandSimulatedTestingofAlgorithmsforSourceMappingandNavigationPathGeneration

Tairan Liu1, Angela Di Fulvio2, Long Kiu Chung3, Kimberlee J.Kearfott3

(1.Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109;2.Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801;3.Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109)

Abstract:Image reconstruction algorithms were developed for radiation source mapping and used for generating the search path of a moving radiation detector, such as one onboard an unmanned aerial vehicle.Simulations consisted of first assuming radioactive sources of varying complexity and estimating the radiation fields that would then be produced by that source distribution.Next, the “measurements” that would result from a pair of adjacent spatial locations were computed.A crude estimate of the source distribution likely to have produced such “measurements” was reconstructed based upon the limited measurements.Location of the next “measurement” was then determined as halfway between the location of the estimated source and the current “measurement.” With each additional sample, improved source distribution reconstructions were made and used to inform the immediate direction of detector motion.Source reconstruction or mapping was formulated as an inverse problem solved with either maximum a posteriori or least squares(LS)regression deconvolution methods.Different amounts of noise were added to the simulated “measurements,” allowing evaluation of the methods’ performances as functions of signal-to-noise ratio of the measured map.As expected, methods that promote sparsity were better suited in reconstructing point sources.Reliable prior information of the source distribution also improved the reconstruction results, especially with distributed sources.With a non-negative least square algorithm and the suggested paths it generated, location of sources was successfully estimated to an accuracy of 0.014 m within nine iterations in a single-source scenario and 12 iterations in a two-source scenario, given a 10% error on the integrated counts and a Poisson distribution of the noise associated with the measured counts.

Keywords: algorithm; computer calculations; detector, radiation; sampling

Health Phys.120(3):321-338; 2021

Patient-specificExtravasationDosimetryUsingUptakeProbeMeasurements

Dustin Osborne1, Jackson W.Kiser2, Josh Knowland3, David Townsend4, Darrell R.Fisher5

(1.University of Tennessee Graduate School of Medicine, Knoxville TN;2.Carilion Clinic, Roanoke, VA;3.Lucerno Dynamics LLC, Cary NC;4.Independent Scholar;5.Washington State University and Versant Medical Physics and Radiation Safety, Richland, WA)

Abstract:Extravasation is a common problem in radiopharmaceutical administration and can result in significant radiation dose to underlying tissue and skin.The resulting radiation effects are rarely studied and should be more fully evaluated to guide patient care and meet regulatory obligations.The purpose of this work was to show that a dedicated radiopharmaceutical injection monitoring system can help clinicians characterize extravasations for calculating tissue and skin doses.We employed a commercially available radiopharmaceutical injection monitoring system to identify suspected extravasation of18F-fluorodeoxyglucose and99mTc-methylene diphosphonate in 26 patients and to characterize their rates of biological clearance.We calculated the self-dose to infiltrated tissue using Monte Carlo simulation and standard MIRD dosimetry methods, and we used VARSKIN software to calculate the shallow dose equivalent to the epithelial basal-cell layer of overlying skin.For 26 patients, injection-site count rate data were used to characterize extravasation clearance.For each, the absorbed dose was calculated using representative tissue geometries.Resulting tissue-absorbed doses ranged from 0.6 to 11.2 Gy, and the shallow dose equivalent to a 10 cm2area of adjacent skin in these patients ranged from about 0.1 to 5.4 Sv.Extravasated injections of radiopharmaceuticals can result in unintentional doses that exceed well-established radiation protection and regulatory limits; they should be identified and characterized.An external injection monitoring system may help to promptly identify and characterize extravasations and improve dosimetry calculations.Patient-specific characterization can help clinicians determine extravasation severity and whether the patient should be followed for adverse tissue reactions that may present later in time.

Keywords: extravasation; internal dosimetry; radiation dose; biokinetics; extremity dose

Health Phys.120(3):339-343; 2021

ElectricalStunGunandModernImplantableCardiacStimulators:UpdateforaNewStunGunModel

Eugenio Mattei, Federica Censi, Giovanni Calcagnini1

(1.Italian National Institute of Health, Department of Cardiovascular, Endocrine-Metabolic Diseases and Aging, Rome, Italy)

Abstract:In 2017, the Italian National Institute of Health conducted a study to evaluate the potential risks of Conducted Electrical Weapons(CEW, AKA “stun guns”)for users bearing a pacemaker(PM)or an implantable cardioverter defibrillator(ICD).The study addressed two specific models of stun guns: the TASER model X2 and AXON model X26P.In 2019, the same experimental protocol and testing procedure was adopted to evaluate the risk for another model of stun gun, the MAGEN model 5(MAGEN, Israel).The MAGEN 5 differs from the previous stun guns tested in terms of peak voltage generated, duration of the shock, and trigger modality for repeated shocks.This note is an update of the previous study results, including the measurements on the MAGEN 5 stun gun.Despite the differences between the stun gun models, the effects on the PM/ICD behavior were the same as previously observed for the TASER stun guns.

Keywords: Electromagnetic fields; exposure, radiofrequency; risk analysis; safety standards

Health Phys.120(3):344-349; 2021

ValidationofaDoseAssessmentMethodtobeUsedin18FFDGLooseContaminationExercises

Miles L.Chen, Lainy D.Cochran, Craig M.Marianno1

(1.Texas A&M University, Department of Nuclear Engineering, College Station, TX 77840)

Abstract:Radiological emergency response may require responders to operate in contaminated environments.To provide more realistic training to these individuals, it has been proposed to disperse low amounts of short-lived radioactive material in simulated emergency scenarios.To demonstrate the applicability and safety of such activities, a limited exercise was conducted where18F was sprayed in a small area and survey activities were executed.A pre-job external radiation exposure dose assessment was performed in preparation for this training.The research presented here compares participant external recorded doses to assessment results in order to validate the dose estimates.Two individuals were used during the dispersion, search, and survey activities.First, a radiation worker mixed 200 MBq Fludeoxyglucose18F with 470 mL H2O in a weed sprayer and distributed it over a 3 m × 3 m area.After evaporation, an exercise participant performed search and survey activities in the area.Actual whole-body doses measured with optically stimulated luminescence dosimeters were 10 ± 1 μSv for both personnel.Whole-body digital dosimeters read 4.3 ± 0.2 μSv and 3.3 ± 0.5 μSv for the radiation worker and exercise participant, respectively.Actual extremity doses were below the dosimeters’ minimum detectable limits for the radiation worker(thermoluminescence dosimeter)and exercise participant(optically stimulated luminescence dosimeter).The dose assessment-predicted whole-body doses were 2.8 ± 0.4 μSv and 3.2 ± 0.1 μSv for the radiation worker and exercise participant, respectively.The estimated dose to the radiation worker’s hand was 21.8 ± 3.8 μSv, and the estimated dose to the exercise participant’s knee was 13.4 ± 0.6 μSv.The study provided substantial evidence for the validity of the dose assessment method, supporting its use for a larger training exercise.

Keywords: operational topics; emergencies, radiological; contamination; dose assessment

Health Phys.120(3):353-359; 2021

UseofDoublevs.SingleRadiationMonitoringBadgeSystemforFluoroscopyUsers

Peter F.Caracappa1, Joseph Weintraub2, Kathleen Krieg3

(1.Department of Environmental Health and Safety, Columbia University, New York, NY;2.Tufts University, Medford MA;3.Amherst College, Amherst, MA)

Abstract:To analyze historical radiation dose data from fluoroscopy users at a major university medical center and compare the impact of two alternate dose monitoring methodologies.Materials and Methods:Interventional radiologists have traditionally worn two radiation monitoring badges to estimate their radiation dose.This study evaluates if a single badge monitoring system can reduce the administrative burden of radiation monitoring without negatively impacting safety or compliance.This study reviewed the dose history data for a 10 y period including 114,500 individual dose measurements.These individuals were each issued two badges for each wear period, including one worn at the collar(outside a protective garment)and one worn at the chest or waist(beneath a protective garment).The dose for each of the badges was derived from the database of personnel dose records.Badges that could be clearly identified as improperly worn were excluded from the study.The EDE as assigned from the two-badge system and as derived from the wear of the collar badge only were both compared to the thresholds for ALARA notifications currently in use.Results:Calculated EDE values are an average of 2.7 times higher when applying a one-badge system as compared to a two-badge system.This is observed to result in a slight increase in the ALARA notification frequency(excluding badges improperly worn in the two-badge system).The overall increase in notification frequency is small because notifications are dominated by dose to the lens of the eye.Conclusion: Although providing less accurate personnel dose estimates relative to a two-badge system, the use of a one-badge monitoring system for fluoroscopy users may have a minimal effect on radiation dose records and “as low as(is)reasonably achievable”(ALARA)notifications, with potentially significant savings in notifications due to improper badge wear, volume of radiation monitoring badges handled, and cost of the radiation monitoring system.

Keywords: operational topics; dosimetry, external; dosimetry, personnel; fluoroscopy

Health Phys.120(3):360-364; 2021