68th Annual Meeting of the Radiation Research Society, Waikoloa Village, HI, October 16-19, 2022
Sergei Tolmachev gave a platform presentation, and Martin Šefl gave two poster presentations at the 2022 Radiation Research Society Meeting in Waikoloa Village, Hawaii.
Actinides in humans: 50-year experience at the U.S. Transuranium and Uranium Registries
Sergei Y. Tolmachev (USTUR)
The United States Transuranium and Uranium Registries (USTUR), and the associated National Human Radiobiology Tissue Repository (NHRTR), is a federal-grant program funded by U.S. Department of Energy and operated by College of Pharmacy and Pharmaceutical Sciences at Washington State University in Richland, Washington, USA. The Registries was established in 1968 to study the biokinetics and internal dosimetry of actinides (uranium, plutonium, and americium) in occupationally-exposed Registrants who volunteered portions of their bodies, or their entire bodies, for scientific use posthumously. The USTUR is the only program worldwide that can comprehensively study biokinetics and dosimetry of internally deposited actinides. The USTUR serves as a source for both scientific research and public information regarding the biokinetics and tissue dosimetry of the actinide elements in humans. Since 1992, eight PhD and eight MS students have used USTUR data to complete the research requirements of their studies. Currently, USTUR research focuses on: (i) estimation of uncertainties in radiation dose assessment for internally deposited actinides, (ii) biokinetic modeling of individual cases, (iii) study of post-mortem distribution of actinides in the human body, and (iv) study of occupational exposure to non-radioactive materials associated with the nuclear industry. The USTUR core operational functions are: (i) accepting and processing Registrant donations, (ii) completing radiochemical analysis of donated tissue samples, and (iii) completing the development and population of the USTUR databases. Currently, the Registries holds records and data for 368 deceased and 21 living Registrants. The USTUR/NHRTR data and materials are available to qualified scientists for their research upon request. The USTUR maintains well-established collaborations with national and international scientists and institutions, and develops new collaborative relationships. Since its establishment, the USTUR has published over 350 peer-reviewed manuscripts, and has contributed to multiple National Council on Radiation Protection and Measurements and International Commission on Radiological Protection publications. [USTUR-0612-22A]
EasySkel: Estimation of plutonium concentration in the skeleton
Martin Šefl (USTUR), Maia Avtandilashvili (USTUR), Joey Y. Zhou (DOE), Sergei Y. Tolmachev (USTUR)
The skeleton is a major plutonium retention site in the human body. Data from the United States Transuranium and Uranium Registries (USTUR) shows that concentration of plutonium varies across different bones and within the bones. For example, the femur is dissected into five bone samples – proximal end, proximal shaft, middle shaft, distal shaft, and distal end, and plutonium concentration for each sample is different. Therefore, the estimation of plutonium activity concentration in the skeleton (Cskel) from limited number of analyzed bone samples is a complex task. Recently, the USTUR has developed a latent bone modelling approach for Cskel estimates based on principal component regression using available data from whole-body tissue donors. The latent bone modeling approach significantly reduced uncertainty of Cskel estimates. This method was implemented in Python 3.9 and accompanied by a simple graphical user interface – EasySkel. EasySkel calculates Cskel and associated uncertainty from two or more measured bone sample concentrations. [USTUR-0617A]
Comparison of latent bone modeling and simple average method for estimating plutonium activity
concentration in human skeleton
Joey Y. Zhou (DOE), Martin Šefl† (USTUR), Maia Avtandilashvili (USTUR), George Tabatadze (USTUR), Sergei Y. Tolmachev (USTUR)
The United States Transuranium and Uranium Registries (USTUR) holds data from 292 partial-body tissue donors for whom only 2 to 8 bone samples were collected at autopsy and radiochemically analyzed for plutonium. The method currently used at the USTUR to estimate skeleton plutonium activity concentrations, simple average method (SAM), implies that the arithmetic average of collected bone sample concentrations represents the total skeleton concentration. The USTUR also holds data from 14 non-osteoporotic whole-body donors for whom ‘true’ values of total skeleton plutonium activity concentrations were estimated based on radiochemical analyses of all measured bones from the right side of the skeleton. A recently developed latent bone model (LBM) applies principal components regression (PCR) to reduce uncertainties in plutonium activity concentration estimates from measurements of a limited set of bone samples. This study used a simulation approach to compare accuracy and precision of the LMB and SAM. The analytical bone dataset consisted of measured plutonium concentrations in up to 90 individual bones from 14 non-osteoporotic whole-body tissue donors. For each simulation run, root mean square errors (RMSEs) were determined for the LBM and SAM, and 10,000 simulations were run for a given number of individual bones (2 to 5). The distributions (mean and standard deviation) of RMSEs obtained from the 10,000 simulations were used to compare accuracy and precision of the LBM and SAM. The results showed that the LBM approach significantly improved the total skeleton concentration estimates. The relative mean (accuracy) reductions of the LBM vs. SAM were 55.5%, 57.4%, 59.1%, and 60.4%; relative standard deviation (precision) reductions were 65.2%, 66.6%, 67.9%, and 68.6% for 2, 3, 4, and 5 bone samples, respectively. [USTUR-0590-21A] †Presenter