Internal Dosimetry Workshop

Tony James, Stacey McCord and Sergei Tolmachev conducted a 2½-day graduate student workshop at USTUR for three Ph.D. dissertation and two M.S. dissertation candidates from Idaho State University’s (ISU) Graduate Program in Health Physics. The workshop was held at the USTUR office on February 12-14, 2010.

Defining New Projects

The workshop primarily focused on establishing research topics for three students who are new to the USTUR/ISU internal dosimetry working group. These projects are summarized below.

Ph.D. student, Majid Khalaf, will be modeling ²⁴¹Am 60 keV and lower energy photon transmission and external detector response for the preserved whole leg of high-level ²⁴¹Am inhalation Case 0846. He will work with a Nuclear Imaging Department in Pocatello to obtain high-resolution serial CT scans of the leg (with the knee flexed and un-flexed) in order to create 3-dimensional computational voxel phantoms by segmenting and rendering the resulting images. This work parallels a study that is being conducted by PhD student, George Tabatadze, using the Case 0102 leg phantom (a tissue-equivalent phantom re-constructed from the ²⁴¹Am-laden hip, leg and foot bones of USTUR’s first whole-body donation).

Master’s student, Shane Weber, will be conducting a reevaluation of the Case 0262 plutonium wound case using Bayesian methodology. This case was previously analyzed in James et al.’s 2007 publication, “USTUR whole body case 0262: 33-y follow-up of PuO₂ in a skin wound and associated axillary node” (link to article). However, an additional part of the original skin wound was located in USTUR’s National Human Radiobiological Tissue Repository (NHRTR) and the plutonium isotopic concentrations (including that of ²⁴¹Pu) measured by high-resolution ICP-MS. This will enable the original external planar germanium detector measurement of ²⁴¹Am and ^239/240Pu to be precisely calibrated, and the total isotopic activities retained at the wound site to be incorporated in a final analysis. Shane will use the UK’s Health Protection Agency-Radiation Protection Division (HPA-RPD) Weighted Likelihood Monte Carlo Sampling code (WeLMoS) to evaluate the posterior probability distributions of the intake and wound absorption parameters, including the absorption characteristics of the ²⁴¹Am contaminant in the original plutonium material.

Master’s student, Joy Epps, will be applying α-particle autoradiography to investigate the postulated long-term chemical binding of Pu inhaled as soluble Pu(NO₃)₄ in bronchial epithelium, and visualize the distribution of Pu previously shown to have been retained for 38 y in the lungs and lymph nodes of USTUR Case 0269 (link to article). The degree of binding and long-term retention of ‘soluble’ actinides in bronchial epithelium is the dominant factor in determining dose to this critical tissue. This is of acute interest in the interpretation of the epidemiological studies being carried out on the Russian Mayak cohort of plutonium workers exposed to soluble forms of plutonium.

WeLMoS Demonstration

Dr. James demonstrated the Integrated Modules for Bioassay Analysis (IMBA) Professional Plus software, and how this integrates with HPA-RPD’s WeLMoS code, using the 0262 plutonium wound case as an example. He showed students how IMBA’s multiple intake regimes are used to determine which combinations of NCRP 156 wound categories best describe the Case 0262 bioassay and autopsy data.

M.S. Access Training

Stacey McCord worked closely with two students, Nino Chelidze and Majid Khalaf, to familiarize them with M.S. Access. Together they discussed how to best design dosage, urine, feces, blood, and autopsy data tables for the primate plutonium biokinetics data (from Dr. Pat Durbin’s Lawrence Berkeley Laboratory) that they are working on. They then created several of these tables in Access and practiced importing data from Excel.