THU-C - Technical Presentations Part 1 Including: Internal Dosimetry, External Dosimetry, Dose Reconstruction, Medical Health Physics, and Academic Institutions Thursday 09/17/20 2:00 PM - 5:20 PM
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| Chair(s): Deepesh Poudel, Richard Vetter
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THU-C.1
2:00 PM Need for Speed and Other Space Force Issues DA Dooley*, MJW Corporation
Abstract: Since the Soviets launched Sputnik in 1959 and put the first astronaut into orbit in 1961, the idea of living in and travelling through space to new worlds remains fascinating to all. With the advent of America's newest branch of the military, the Space Force, a brighter light has been shown on the strategic significance of the objects orbiting our planet and life in space. While radiation exposure to space travelers has been studied and is a significant concern for extended periods in orbit and beyond, space presents a myriad of physical and phycological challenges that are rarely discussed. This paper will explore the entire gambit of space travel pitfalls including establishing living quarters on nearby moons and planets in the future and what it will take to make this a reality.
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THU-C.2
2:15 PM OSLDs on a Plane—Measuring Radiation Dose to Airline Passengers DB Schultz*, United States Military Academy
Abstract: Radiation doses received by passengers traveling on airplanes is a topic of some interested. We have begun a program of giving people in our department who are traveling by air OSLDs to carry with them on the airplanes. We will present our data from our fourth quarter 2019 program with comparisons with dose estimates from the Federal Aviation Administration CARI-6 online calculator.
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THU-C.3
2:30 PM Development of a new chelation model: Bioassay data interpretation and dose assessment after plutonium intake via wound and treatment with DTPA S Dumit*, Los Alamos National Laboratory
; G Miller, Santa Fe, NM; JA Klumpp, Los Alamos National Laboratory; D Poudel, Los Alamos National Laboratory; L Bertelli, Los Alamos National Laboratory; TL Waters, Los Alamos National Laboratory
Abstract: The administration of chelation therapy to treat significant intakes of actinides, such as plutonium, affects the actinide’s normal biokinetics. In particular, it enhances the actinide’s rate of excretion, such that the standard biokinetic models cannot be directly applied to the chelation-affected bioassay data in order to estimate the intake and assess the radiation dose. The present study proposes a new chelation model, which can be applied to the chelation-affected bioassay data after plutonium intake via wound and treatment with DTPA. In the proposed model, chelation is assumed to occur in the blood, liver, and parts of the skeleton. Ten datasets, consisting of measurements of 14C-DTPA, 238Pu, and 239Pu, involving humans given radiolabeled DTPA and humans occupationally exposed to plutonium via wound and treated with chelation therapy, were used for model development. The combined dataset consisted of daily and cumulative excretion (urine and feces), wound counts, measurements of excised tissue, blood, and post-mortem tissue analyses of liver and skeleton. The combined data were simultaneously fit using the chelation model linked with a plutonium systemic model, which was linked to an ad hoc wound model. The proposed chelation model was used for dose assessment of the wound cases used in this study.
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THU-C.4
2:45 PM Risk-Benefit Analysis of Medical Intervention for Incorporated Plutonium LM Pinckard, Los Alamos National Laboratory
; JA Klumpp*, Los Alamos National Laboratory; D Poudel, Los Alamos National Laboratory; S Dumit, Los Alamos National Laboratory; L Bertelli, Los Alamos National Laboratory
Abstract: Incorporated plutonium can be treated via administration of chelating agents – specifically, Ca- and Zn-DTPA. When the intake occurs via wound, surgical excision of the wound site may also be considered. Guidance regarding when to offer treatment varies drastically between various guidelines, recommendations, and policies dealing with radiation exposures. In principle, an ideal treatment decision would weigh the expected risks of treatment against the risks of non-treatment. However, it is always assumed, implicitly or explicitly, that chelation and surgical intervention have minimal lasting adverse effects. In this work, the medical and bioassay records of approximately 200 employees of Los Alamos National Laboratory were examined with the goal of determining the benefits and possible adverse effects resulting from medical intervention. Several interviews with employees with a history of plutonium intake were also conducted to further this goal. A major finding was that long-term medical follow-ups of employees following plutonium intakes were almost never conducted. Furthermore, when follow-ups were conducted (via medical personnel or by interviews conducted for this work) it was found that adverse effects of treatment lasting many years after the incident, although minor compared to cancer, were not uncommon. This suggests that the conventional wisdom that chelation and surgical excision do not result in significant long-term adverse effects is not derived from the absence of adverse effects but rather from a failure to look for them.
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THU-C.
3:00 PM BREAK
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THU-C.5
3:10 PM Long-term retention of plutonium in the respiratory tracts of two acutely-exposed workers D Poudel*, Los Alamos National Laboratory
; M Avtandilashvili, USTUR, Washington State University; L Bertelli, Los Alamos National Laboratory; JA Klumpp, Los Alamos National Laboratory; SY Tolmachev, USTUR, Washington State University
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 presentation 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. Comparison of the activity concentration and total activity in the lungs and the thoracic lymph nodes provided information on the long-term solubility of the material inhaled. The materials inhaled by both workers were found to have solubility in between that of plutonium nitrates and oxides. 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 data from these 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, fb) of 1% and 4%, without having to significantly alter the particle clearance parameters. Effect of different assumptions about the bound fraction on radiation doses to different target regions was also investigated. For inhalation of soluble materials, an assumption of fb of 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%. Possible alternate methods of explaining higher-than-expected long-term retention of plutonium in the upper respiratory tract of these individuals – such as uptake by lungs, and material sequestration into the scar tissues – are also discussed.
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THU-C.6
3:25 PM Dosimetry and Health Physics Aspects of Therapeutic Uses of Lu-177 DOTATATE MG Stabin*, NV5/Dade Moeller
Abstract: Lu-177 DOTATATE (Lutathera) is a radiopharmaceutical used to treat gastroenteropancreatic neuroendocrine tumours. The beta emissions from Lu-177 induce cellular damage in somatostatin receptor-positive cells and neighboring cells. Several GBq of the compound are given approximately every 8 weeks in 4 IV administrations. Progression Free Survival (PFS) rates over 2 years are typically around 65%. The radiation dosimetry has been well established in a number of biokinetic studies in human subjects. Interestingly, the photon yield is low enough that the dosimetry for individual patients can be established using images taken after the first therapy administration. The health physics aspects during the administration of the drug are considerable, and involve many hours of room preparation and decontamination. The dosimetry and healthy physics aspects will be described in this talk, with examples taken from direct patient care experiences.
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THU-C.7
3:40 PM Medical Radiation Exposure of Patients in the United States FA Mettler, University of New Mexico
; M Mahesh, Johns Hopkins University School of Medicine; MB Chatfield, American College of Radiology; CE Chambers, Penn State Hershey Medical Center; JG Elee, Louisiana Department of Environmental Quality; DP Frush, Stanford University Medical School; MT Milano, University of Rochester Medical Center; DL Miller, U.S. Food and Drug Administration; HD Royal, Washington University; DC Spelic, AJ Ansari, WE Bolch, GM Guebert, RH Sherrier, JM Smith, RJ Vetter*, U.S. Food and Drug Administration, U.S. Centers for Disease Control and Prevention, University of Florida, Logan University, U.S. Department of Veterans Affairs, Emory University, National Council on Radiation Protection and Measurements
Abstract: In 2018 the National Council on Radiation Protection and Measurements (NCRP) appointed a committee to examine new literature and updated medical source databases to assess changes in number and types of medical radiation procedures and average per caput and collective effective doses since 2006, the last time medical exposures were evaluated. The Committee used peer reviewed published data and official government data and analyzed data from insurance companies and commercial sources, such as IMV survey data, Medicare files, and U.S. Department of Veterans Affairs records. Findings of the Committee were published as an update of NCRP Report No. 160, Ionizing Radiation Exposure of the Population of the United States, Section 4 (Medical Exposure of Patients) (2009). The new Report (NCRP Report No. 184; 2019 ) evaluates average individual effective dose and collective effective doses from medical exposures for the 2016 timeframe. The Report pays particular attention to those procedures that contribute the largest share and provides information on nominal effective dose values that individual patients may experience from specific examinations. These effective dose values should not be used as an indication of acceptability or to estimate individual cancer risk from a certain radiation procedure, but rather used as a metric to broadly compare the magnitude of potential stochastic effects to populations from different radiation sources. This Report does not quantify associated health risks nor discuss potential medical benefits. The Report also does not specify any actions that should be taken in light of these latest data. It provides indices for comparison among radiation sources and at different time periods. The Report concluded that the largest contributor to collective effective dose and effective dose per individual in the population (CT scanning) has stabilized and the second largest contributor (nuclear medicine) has decreased substantially from 2006.
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THU-C.8
3:55 PM An Experience with a Patient Passing Post-Lutathera Treatment RP Harvey*, Roswell Park Comprehensive Cancer Center
Abstract: Patients diagnosed with gastroenteropancreatic neuroendocrine tumors (NETs) may be treated with radiopharmaceutical therapy. This peptide receptor radiopharmaceutical therapy is performed with 177Lu Dotatate or Lutathera and it has shown promise for these patients. Patients with NETs generally exhaust other conventional treatments and may choose this treatment as a last resort. Unfortunately these patients may be very ill and possibly approaching end of life. The potential exists for a Luthathera patient to pass away with a therapeutic dose administered during the four dose regimen given eight weeks apart. This situation occurred with a patient being treated with Lutathera by Roswell Park Comprehensive Cancer Center.
A male patient with NETs was treated three times with 7.4 GBq of Lutathera at each dose administration. The first two treatments were well tolerated but the patient was not doing as well when he arrived for his third treatment. The decision was made to treat the patient and sadly the patient passed away the evening/night of the third administration of Lutathera. Lutathera treatments are an outpatient procedure with a fairly long infusion time so the patient passed in their home rather than at the treatment center location. The Director of Radiation Safety and Radiation Safety Officer was notified the next day.
The passing of a patient having been administered a radiopharmaceutical therapy dose is relatively rare but we all need to be prepared for this possibility when treating radiopharmaceutical therapy patients. Most facilities have included this prospect in their radiation safety programs but the actual occurrence poses some challenges if not appropriately prepared. The variability and uncertainty that exists almost guarantees that each situation will present different circumstances that the licensee may not be prepared for. This event at Roswell Park Comprehensive Cancer Center was an unfortunate circumstance but a positive learning experience and provided an opportunity for growth. As radiopharmaceutical therapies increase and new therapies are developed, the probability of these unfortunate incidents increases. An experience of this nature provides the opportunity to share knowledge, lessons learned and additional education to those that may be affected by these outcomes whether they are in the field of radiation protection or end-of-life services.
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THU-C.
4:10 PM BREAK
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THU-C.9
4:20 PM Is There Justification to Modify Lutathera Patient Release Instructions CE Pagan*, University of Texas Southwestern Medical Center
; JA Anderson, Ph.D., University of Texas Southwestern Medical Center; PA Jenkins, Ph.D, University of Utah Health; MJ Amen, University of Texas Southwestern Medical Center; SZ Revell, University of Texas Southwestern Medical Center; OK Oz, UTSW; L De Blanche, UTSW
Abstract: The intent of this study was to examine the release instructions for patients administered Lu-177 DOTATE (Lutathera) and determine if the restrictions on the patient can be eased. Current practice uses a 2-3 day time frame for the patient to avoid prolonged contact with family members, and up to a week for children and pregnant women. Through a more patient-and-family-centric approach, reducing the duration of the safety precautions could ease some of the strain placed on families in the days following treatment. The data collected in this study was a collaborative effort between the University of Texas Southwestern Medical Center and the University of Utah Health. The preliminary patient population was composed of 24 patients, each administered 200 mCi of Lu-177 DOTATE. Patient exposure rates were taken immediately after the Lutathera infusion and at the completion of the treatment day. The body-mass-index (BMI) was recorded for each patient as part of this study to determine if there was a correlation between BMI and exposure rates or a decrease in exposure rates. Patients receiving modified doses, and previously measured patients were excluded from the study. The average initial exposure rate was 4.1 mR/h, and at release the average dose was 2.4 mR/h. This was a 40% decrease in exposure rates over an average of 3.3 hours. From the initial patient population there appears to be no correlation between patient BMI and the initial exposure rate or the amount the exposure rate decreases during the patients stay. The implications of these results for modifying patient release instructions using the methods of NCRP 155 continue to be evaluated.
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THU-C.10
4:35 PM The Nuclear Regulatory Commission’s Outreach to University Students and Faculty EE Hickey, Pacific Northwest National Laboratory
; CA Condon*, Pacific Northwest National Laboratory; B McDowell, Pacific Northwest National Laboratory; V Shaffer, Nuclear Regulatory Commission; S Bush-Goddard, Nuclear Regulatory Commission
Abstract: The Nuclear Regulatory Commission’s (NRC’s) Radiation Protection Computer Code Analysis and Maintenance Program (RAMP) includes radiation protection and dose assessment computer codes that encompass nuclear power plant licensing (e.g., reactor siting, design-basis accidents, and normal effluent releases), emergency response and severe accidents, atmospheric transport and dispersion, and site decommissioning. This presentation describes how NRC is working with university faculty and students to build an academic network of RAMP users. RAMP membership provides free access to all the codes in RAMP for qualified students and faculty, as well as on-line training materials, the latest code releases, and code forums. Encouraging the use of the RAMP codes provides benefits to the NRC, universities and participating faculty and students. NRC will benefit as student and faculty use of the codes increases RAMP adoption and improves RAMP codes. University students study and develop new technology and research, making them excellent sources of input for innovation, improvement of the models and codes, and identification of needs for new RAMP codes. Furthermore, active student and faculty users can test codes and report any issues or errors to the NRC, thus improving code quality. Students benefit by using the RAMP codes for their study and research, thus obtaining exposure to real-world problems and adding value to their future careers. Collaborating with the NRC benefits faculty and universities by helping grow their nuclear engineering and health physics programs. Encouraging students and academic institutions to use the RAMP suite of codes will also help build and sustain the important national capability for radiological protection and dose assessment. [PNNL-SA-150396]
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THU-C.11
4:50 PM VADER: A Variable Dose-Rate External Cs-137 Irradiator for Internal Emitter and Low Dose Rate Studies TL Morgan*, Columbia University in the City of New York, Versant Medical Physics
; DJ Brenner, Columbia University in the City of New York; G Garty, Columbia University in the City of New York
Abstract: Beyond prompt irradiation, Cs-137 is likely to be the most biologically important agent released in many accidental (or malicious) radiation exposure scenarios. Cs-137 either can enter the food chain, and be consumed, or, if present in the environment, (e.g. fallout) can provide external irradiation. In either case, due to the high penetration of the 662 keV gamma rays emitted by Cs-137, the individual will be exposed to a uniform, whole body, irradiation at low dose rates. The VADER (VAriable Dose-rate External Cs-137 irradiatoR) allows modeling these exposures, bypassing many of the problems inherent in internal emitter studies. Making use of discarded Cs-137 brachytherapy seeds, the VADER can provide varying low dose rate irradiations at dose rates of 0.1 to 1.2 Gy/day. The VADER includes a mouse “hotel”, designed to allow long term simultaneous residency of up to 15 mice. Two source platters, containing ~250 mCi each of Cs-137 brachytherapy seeds, are mounted above and below the cage and can be moved under computer control to provide constant low dose rate or a varying dose rate mimicking Cs-137 biokinetics in mouse or man. We present the VADER design and characterization of its performance.
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THU-C.12
5:05 PM Total Measurement Uncertainty Analysis for Polypropylene Sample Containers by Utilizing the Probabilistic In Situ Object Counting System Uncertainty Estimator for Gamma Spectroscopy Analyses JE Zamora-Nunez*, Perma-Fix Environmental Services
; AU Lopez, Perma-Fix Environmental Services
Abstract: A measurement without an associated uncertainty is fundamentally incomplete. It is not possible to interpret the quality of the data presented without an estimation of its uncertainty. Consequently, it is imperative to determine the parameters that contribute to the measurement’s total uncertainty and their associated impact. This paper presents the methodology used to determine the total measurement uncertainty associated with gamma spectroscopy analyses of soil samples while utilizing high purity germanium detectors to quantify the concentration of naturally occurring radioactive material (NORM) or technologically enhanced naturally occurring radioactive material (TENORM) using in semi-crystalline high-density polypropylene sample containers. For many customers with NORM and TENORM samples, the radionuclides of concern are Ra-226 & Ra-228 (total radium). For this experiment, Ra-226 and Ra-228 (Ac-228) were quantified by their 186 keV and 911 keV photopeaks, respectively. The parameters that affect the measurement’s uncertainty include the “as-calibrated” and “as-measured” sample container characteristics, matrix composition, and fill height. In order to quantify the impact of these not-well-known factors and improve the quality of the associated total measurement uncertainty, the In Situ Object Counting System (ISOCS) Uncertainty Estimator, developed by Mirion Technologies, was used. The ISOCS Uncertainty Estimator was used to perform probabilistic tests on the sample containers by creating 1000 models in which the container density, fill height, inside diameter, and sample material density parameters were varied on a stochastic manner to establish the sensitivity associated with these parameters and their contribution to the total measurement uncertainty. The results from the probabilistic tests show that refining the aforementioned parameters improves the total measurement uncertainty between 34% and 49% for the 186 keV and 911 keV photopeaks, respectively.
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