Health Phys. Abstracts，Volume 121,Number 5

Age-dependentRadiationDoseRatesfromCanineSn-117mTreatments

Matthew G. Arno1, Chad Smith2

(1. Foxfire Scientific, Arlington, TX；2. FX Masse, Gloucester, MA)

Abstract:Tin-117m (Sn-117m) is used to treat dogs with osteoarthritic joints by radiosynoviorthesis. The decay process for Sn-117m is internal conversion wherein IC electrons and auger electrons provide the therapeutic effect. Additionally, the most prominent gamma emission is 158.6 keV. The effective dose rate received by a person interacting at close distances with a treated dog is needed to determine the person’s total dose and thus regulatory compliance. Simple measurement of the dose rate at a given distance does not provide an accurate measurement of the effective dose to a person due to the non-uniform nature of the radiation field at close distances. MNCP models of the interactions of five ages of humans at three distances were created to determine the effective dose rates using the methodology from NRC Regulatory Guide 8.40. Ratios of the effective dose rate to the person to the measured dose rate at 1 m from the same source were calculated.

Keywords: dogs; dose assessment; Monte Carlo; radiation protection

Health Phys. 121(5):447-453; 2021

RadiationProtectionEvaluationofMedicalX-rayImagingCentersinQazvin,Iran

Azam Janati Esfahani1,2, Susan Cheraghi3,4

(1.Department of Medical Biotechnology, School of Paramedical Sciences, Qazvin University of Medical Sciences, Qazvin, Iran;2. Cellular and Molecular Research Center, Research Institute for Prevention of Non-Communicable Diseases, Qazvin University of Medical Sciences, Qazvin, Iran;3. Radiation Biology Research Center, Iran University of Medical Sciences, Tehran, Iran;4. Department of Radiation Sciences, Faculty of Allied Medicine, Iran University of Medical Sciences, Tehran, Iran)

Abstract:Given the potential risks of X rays in imaging, it is necessary to evaluate the radiation safety of medical X ray imaging rooms and radiation information of radiographers. A descriptive study has been carried out in Qazvin, Iran, in the form of a questionnaire answered by radiography technologists in private and public imaging centers to assess the level of knowledge, attitude, and performance about X ray exposure and safety against it. Afterward, the radiation doses of public areas of the radiography centers were measured by a survey meter. A checklist was also completed, containing items about availability of ventilation facilities in X ray rooms, radiation warning signs, radiation work schedules, documents of periodic blood test monitoring, exposure history of radiographers by film badge, and documents of the quality control of X ray devices. The data analysis was performed by SPSS 16 using descriptive study,t-test, ANOVA, and Pearson’s correlation coefficient test. The mean attitude and knowledge scores were 6.65±1.63 out of 9 and 4.82±2.06 out of 15, respectively. Sex, age, and workplace had no significant effect on the radiographers’ knowledge and attitude, while occupational experience had a negative relationship, and level of education had a significant direct association with knowledge of the participants (p-value<0.05). The performance of the staff was somewhat good. Almost all X ray imaging centers had good radiation protection conditions. The annual quality control of X ray imaging devices was ensured. The radiation protection awareness among the medical radiographers in Qazvin city needs to be improved, especially among the experienced staff.

Keywords: medical radiation; occupational safety; radiation protection; X rays

Health Phys. 121(5):454-462; 2021

EvaluationoftheCorrectionMethodsUsingAgeandBMIforEstimatingCTOrganDoseUsingaRadiophotoluminescenceGlassDosimeterandaMonteCarlo-basedDoseCalculator

Weishan Chang1,2, Yusuke Koba2

(1.Department of Radiological Sciences, Faculty of Health Sciences, Tokyo Metropolitan University, 7-2-10, Higashiogu, Arakawa-ku, Tokyo 116-8551, Japan;2. Center for Radiation Protection Knowledge, National Institute of Radiological Sciences, QST, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555, Japan)

Abstract:The size-specific dose estimates (SSDE) have been recommended to replace the volume computed tomography dose index (CTDIvol) because it takes patient size into account. On the other hand, organ dose is thought to be a more appropriate quantity in the radiation protection field due to its correlation with radiation risk. The web-based computed tomography (CT) dose calculator WAZA-ARIv2 only offers organ doses for adults with four different body shapes and for children with five different ages. Since the American Association of Physicists in Medicine (AAPM) offers the conversion factors for SSDE and the correlation of SSDE with organ dose has been demonstrated, implementation of the conversion table might improve the accuracy of WAZA-ARIv2. This study aimed to evaluate a body mass index (BMI)-based and age-based correction method for estimation of the organ dose by using a radiophotoluminescence dosimeter (RGD), an anthropomorphic phantom, and the dose calculator WAZA-ARIv2. RGDs were individually calibrated by using an ISOVOLT TITAN-320 X ray generator. The ratio of the SSDE conversion factors (CFSSDE) was used as the comparison index. For the BMI-based correction method, the ratio ofCFSSDEvalues for the adult phantoms was expected to be 1.065, and the average ratio of the organ doses for the adult phantoms was 1.163±0.169. For the age-based correction method, the ratio ofCFSSDEvalue for 5- and 10-y-old pediatric phantoms was expected to be 0.889, and the ratios of the organ doses were 0.866±0.024 and 0.909±0.047 for the WAZA-ARIv2 dosimetry system and RGD dosimetry system, respectively. In conclusion, both evaluations of the experimental results showed the consistency between WAZA-ARIv2 and the SSDE conversion factor table. Moreover, the importance of taking the measurement position into account when applying the mass attenuation coefficient was demonstrated according to this study.

Keywords: computed tomography; dose； organ; dosimetry; Monte Carlo

Health Phys. 121(5):463-470; 2021

OrganDoseReconstructionApplicableforaJapaneseNuclearWorkerCohort:J-EPISODE

Hiroshige Furuta1, Kaoru Sato2, Akemi Nishide3, Shin’ichi Kudo1, Shin Saigusa1

(1. Institute of Radiation Epidemiology, Radiation Effects Association, 1-9-16 Kaji-cho, Chiyoda-ku, Tokyo 101-0044, Japan;2. Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195, Japan;3. Ibaraki Christian University, 6-11-1 Omika, Hitachi, Ibaraki 319-1295, Japan; formerly at Institute of Radiation Epidemiology, Radiation Effects Association)

Abstract:An evaluation of cancer risk based on organ-absorbed dose is underway for the Japanese Epidemiological Study on Low-Dose Radiation Effects (J-EPISODE), which has analyzed health effects in association with radiation exposure evaluated with the personal dose equivalentHp(10). Although the concept of effective dose and its operational definition ofHp(10) are widely used for radiological protection purposes, effective dose is not recommended for epidemiological evaluation. Organ-absorbed dose was instead adopted for the IARC 15-Country Collaborative study (15-Country study), the International Nuclear Workers Study (INWORKS), the Mayak worker study, and the Life Span Study (LSS) of atomic bomb survivors. The reconstruction method in J-EPISODE followed in principle the approach adopted in the 15-Country Study. As part of the approach of J-EPISODE, a conversion factor from photon dosimeter reading to air kerma was developed using dosimeter response data, which were measured by the experiment using an anthropomorphic phantom, and it was confirmed that the 15-Country study’s assumption of photon energy and geometry distribution in a work environment applied to Japanese nuclear workers. This article focuses on a method for reconstructing the conversion factor from photon dosimeter reading to organ-absorbed photon dose for a Japanese nuclear worker cohort. The model for estimating the conversion factor was defined under the assumption of a lognormal distribution from three concerned bias factors: (1) a dosimeter reading per air kerma, i.e., dosimeter response; (2) an organ-absorbed dose per air kerma; and (3) a factor relating to the differences in dose concepts and calibration practices between the roentgen dosimeter era and the present. Dosimeter response data were cited from the companion paper. Data on organ-absorbed photon dose per air kerma were estimated using a voxel phantom with the average Japanese adult male height and weight. The bias factor for the recorded dose in the roentgen era was defined, considering the backscatter radiation from the human body. The estimated values of organ-absorbed photon dose per air kerma were almost the same as those in ICRP Publication 116, revealing that the effect of differences in body size was almost negligible. The conversion factors from dosimeter reading to organ-absorbed dose were estimated by period (the roentgen era or from then), nuclear facility type (nuclear power plant or other), dosimeter type, and tissue or organ. The estimated conversion factors ranged from 0.7 to 0.9 (Gy Sv-1). The estimated cumulative organ-absorbed photon dose for the participants of J-EPISODE demonstrated that organ-absorbed dose values were approximately 0.8 times the recorded doses if neglecting dose-unit differences. J-EPISODE reconstructed an organ-absorbed dose conversion factor and will evaluate the risk of cancer mortality and morbidity using the organ-absorbed dose in the future.

Keywords: dose； organ; dosimetry; external; epidemiology; nuclear workers

Health Phys. 121(5):471-483; 2021

Pu-239AccumulationinE.ColiandP.PutidaGrowninLiquidCultures

Lisa Manglass1,2, Molly Wintenberg3, Mark Blenner3, Nicole Martinez1

(1.Center for Nuclear Environmental Engineering Sciences and Radioactive Waste Management (NEESRWM), Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC;2.Department of Physics and Engineering, Francis Marion University, Florence, SC;3.Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, SC)

Abstract:Understanding of the behavior and effects of plutonium (Pu) in the environment is an important aspect of developing responsible and effective strategies for remediation and environmental stewardship. This work studies the sorption and uptake of239Pu by common environmental bacteria,EscherichiacoliDH10β andPseudomonasputidaKT-2440. Plutonium was directly incorporated into growth media prior to inoculation (0.12 kBq mL-1), and samples from the liquid cultures ofE.coliandP.putidawere analyzed over a 15 d growth period through liquid scintillation counting (LSC) of plutonium in cell pellets and cell culture media following centrifugation. To improve its solubility in the liquid cultures, Pu was complexed with citrate prior to inoculation.P.putidacultures were also grown without citrate to examine potential impact ofP.putida’sability to use citrate as a food source. The accumulation of Pu inP.putidacells was found to increase both with and without citrate complexation for the first 5 d and then plateau until the end of the study period (15 d). A higher activity concentration of Pu was found inP.putidacells grown with citrate complexation than without. The activity concentration of plutonium inE.colicells was greater than that inP.putidacells, which may be the result of a stronger complexing agent made byE.colifor the purpose of iron uptake. There are a variety of factors that influence Pu behavior in bacterial systems, and results confirm that even in a simple system, multiple mechanisms are at play.

Keywords: bacteria; plutonium; radiation; low-level; waste management

Health Phys. 121(5):484-493; 2021

InterpretationofEnhancedFecalandUrinaryPlutoniumExcretionDataundera2yRegularDTPATreatmentStartedMonthsafterIntake

Olivier Grémy1, Nicolas Blanchin2, Laurent Miccoli1

(1.CEA, Direction de la Recherche Fondamentale, Institut de Biologie François Jacob, Université Paris-Saclay, Fontenay-aux-Roses, France;2.CEA, Service de Santé au Travail, Saint-Paul-Lez-Durance, France)

Abstract:In a worker who had internalized plutonium, most likely through inhalation of a somewhat soluble compound, an extensive diethylenetriaminepentaacetate (DTPA) treatment regimen was initiated several months after contamination. Numerous radiotoxicological analyses were performed in both fecal and urinary specimens collected, sometimes for three consecutive days after DTPA administration. Activity measurements showed the continued effectiveness of DTPA intravenous infusions in removing plutonium from tissues of retention even if the treatment regimen started very belatedly after contamination. In the present case, the activity excreted through urine within the first 24 h after a DTPA infusion contributed only about half of that activity excreted within the first three days (i.e., the cumulative activity of the first three 24 h urine collections). In addition, the careful study of the data revealed that DTPA-induced excretion of plutonium via fecal pathway significantly contributed to the overall decorporation. The intracellular chelation of plutonium may be responsible for this enhanced excretion of activity in feces as well as for the delayed and sustained increased clearance of activity in urine. The authors would suggest that the occupational physicians offer to individuals who internalized moderately soluble or soluble plutonium compounds undergo a long-term DTPA treatment, especially when it is not initiated promptly after intake. Under this scenario, measurements of plutonium in successive urine and fecal collections after treatment should be required to get a better estimate of the therapeutic benefit. Also, intracellular chelation and fecal route should be taken into account for better interpretation of radiotoxicological data and modeling of plutonium kinetics under delayed DTPA treatment.

Keywords: chelation; DTPA; exposure; occupational; plutonium

Health Phys. 121(5):494-505; 2021

EvaluationofRadiationShieldingRequirementsandSelf-shieldingCharacteristicsforaNovelRadiosurgerySystem

Qinjian Cao, Jun Tan, Yue Ren, Wanchun Xiong, Xiaofeng Wei, Wei Cheng1

(1. China Institute for Radiation Protection, Taiyuan, China)

Abstract:In order to provide safe operating conditions for radiation workers and the public at large, the radiation shielding for radiotherapy treatment rooms will have to be determined by an expert physicist according to the applicable radiation control regulations. A new radiosurgery system with integrated self-shielding, called the Zap-X, obviates the need for costly and complex radiation bunkers. Radiation levels in the vicinity of the ZAP-X radiosurgery system were acquired for a number of different operating conditions, and a 3D radiation dose distribution was measured for better visualization of hot spots and the general dose distribution. The radiation shielding requirements were evaluated according to the International and Chinese standards, respectively. While the integral self-shielding of the Zap-X was designed in accordance with international standards, it was found to be insufficient for Chinese standards. In order to meet the needs of the growing new generation of radiotherapy equipment, several suggestions for improvement of Chinese standards are proposed.

Keywords: radiation protection; radiation; medical; safety standards; shielding

Health Phys. 121(5):506-512; 2021

TheEffectofSteppingBackFromtheX-RayTableonOperatorRadiationExposure

Robert F. Wilson1, John P. Gainor2, Blair Allen2

(1.Cardiovascular Division and Advanced Preclinical Imaging Center University of Minnesota Minneapolis, 420 Delaware Street SE, MMC 508, Minneapolis, MN 55455;2. Egg Medical, Inc. Arden Hills, MN)

Abstract:Background: Nearly all radiation safety courses teach that scatter radiation around the X-ray table falls with the inverse of the distance from the imaging site. Humans, however, are complex X-ray reflectors and the application of the inverse square law to clinical imaging is only assumed.Methods: We measured scatter radiation at two positions where staff commonly stand around the X-ray table. Using an anthropomorphic human phantom, human and pig cadavers, and a glass sphere, we measured scatter radiation levels in each position, and then 2- and 3-fold the distance from the imaging site. We compared the measured scatter radiation to that predicted by the common inverse square law and a more detailed geometric inverse square law.Results: In all but the glass sphere, scatter radiation was much higher below the table (68%-74% of all scatter radiation, depending on model and position) than above the table (26%-32% of scatter radiation,p<0.01). Scatter radiation fell with increasing distance from the table, but above the table both inverse square laws significantly over-estimated the benefit of stepping back (19%-93% overestimation by geometric inverse square law at 2-fold distance, 14%-46% at 3-fold). In addition, a pelvis in the phantom appeared to cause significant scatter radiation field anomalies at the angiographer position.Conclusion: Stepping back from the table does not reduce scatter radiation levels as much as the inverse square law predicts. The geometric inverse square law best predicts the reduction in scatter radiation below the table, but above the table it too overestimates the benefit of stepping back. The irregularity of the scatter radiation field should be taken into account by scatter radiation shielding systems.

Keywords: diagnostic radiology; radiation dose; radiation protection; X-ray imaging

Health Phys. 121(5):522-530; 2021

ContaminationResultingFromaBroken125ISeedDuringaBrachytherapyProcedure

Lesley Buckley, Danielle J. Fraser, Miller MacPherson, Claire Foottit1

(1. The Ottawa Hospital Department of Medical Physics, 501 Smyth Rd, Box 927, Ottawa, ON K1H 8L3)

Abstract:Brachytherapy programs within radiation therapy departments are subject to stringent radiation safety requirements in order to ensure the safety of the staff and patients. Training programs often include brachytherapy-specific radiation safety training modules that address the specific risks associated with radioactive sources, emergency procedures, and regulatory requirements specific to the use of radioisotopes. Unlike other uses of radioactive materials, brachytherapy uses sealed sources and therefore under routine operations does not encounter radioactive contaminants. This article presents an unusual clinical situation in which an125I brachytherapy seed was damaged during routine clinical workflow, resulting in radioactive contamination within the clinical environment. Decisions made at the time of the incident resulted in contamination that spread beyond the initial location. The incident highlighted a shortcoming of the radiation safety program in preparing staff for the possibility of having to deal with unsealed radioactivity. Brachytherapy programs would be strengthened by including training specific to radioactive contamination in their emergency training to equip staff to respond to unexpected damage to the sealed sources.

Keywords: operational topics;125I; brachytherapy; contamination

Health Phys. 121(5):531-534; 2021