1. Interpretation of Urinary Excretion Data from Plutonium Wound Cases Treated with DTPA
D. Poudel, L. Bertelli, J.A. Klumpp, T.L. Waters
Radiation Protection Division, Los Alamos National Laboratory
HPS Annual Meeting 2017
Raleigh, NC
LA-UR

2. Introduction
Behavior of chelate (Pu- DTPA) dominates that of Pu; Systemic models no longer valid
Several empirical methods; no consensus model
Different methods discussed

3. Data Several 239Pu wound cases Chelated at least once
Not confounded by significantly larger previous intakes
Excluded cases without proper recordings of the times and number of chelation treatments

4. Data
Case 1:
Left index finger, working with Pu metals
29 treatments including one on 590d post intake
Case 2:
Deposition of a metallic fragment on the right thumb
4 treatments within the first week of intake
No fixed protocol for collecting bioassay after DTPA treatment then
Samples collected around and after 100d after the last chelation
Case 1 followed for ~3y; Case 2 for ~7y

5. Biokinetic Models NCRP 156 Wound Model Leggett’s Pu Systemic Model
ICRP 100 HATM

6. Biokinetic Models

7. Maximum Likelihood Analysis
Maximum likelihood method (IDEAS Guidelines)

8. Maximum Likelihood Analysis

9. Evaluation of Affected Data
Empirical urinary excretion model (Hall et. al. 1978)
Compact description of the method (La Bone 2002)

10. Evaluation of Affected Data

11. Evaluation of Affected Data
Parameter
Value
Source
Enhancement factor
1 to 130
Norwood 1962, Anderson et al. 1970, Jech et al. 1972, Jolly et al. 1972, Parker 1973, Schofield and Lynn 1973, Hall et al. 1978, Piechowski et al. 1989, La Bone et al. 1994a and b, Bailey et al. 2003, James et al. 2008, Bertelli et al. 2010, Davesne et al. 2016 h1
0.1 to 1d
Majority of chelate is excreted within a day (Stather et al. 1983; Durbin et al. 1987) h2
1 to 10d
DTPA effect may last from a few weeks up to 100d post chelation (Schofield et al. 1973; Jech et al. 1972; Davesne et al. 2016)

12. Evaluation of Affected Data

13. Bayesian Analysis Bayesian MCMC Internal Dosimetry Code (LANL)
Equal probability is assigned to several biokinetic models (priors)
Analysis of data 100d post last chelation
Predominance of “LANL Soluble” form

14. Comparison of Results
MLA resulted in intakes approximately twice as large as Bayesian analysis
Differences in model assumptions

15. Discussion – Hall’s Method
Hall’s method is largely empirical
Information on E and the behavior of chelate
E of 12.5 and 20.5
Allows to calculate the “actual intakes” had there been no chelation
Requires no “waiting time” (e.g., 100d after last chelation)
Determine efficacy of chelation

16. Discussion – Intracellular Action of DTPA?
Significant urinary enhancement when tc = 590d
Near-negligible amount of Pu in the blood or ECF
Lends support to the hypothesis that DTPA may decorporate Pu in intracellular sites as well (Fritsch et al ; Gremy et al. 2016)
Liver known to be a site of DTPA influence (e.g., Roedler et al. 1989; Breitenstin and Palmer 1989)
Observation important for compartmental modeling approaches; several models have recognized (e.g., Fritsch et al. 2007; Breusted et al. 2009; Konzen and Brey 2010)
From bone surfaces and bone marrow? (e.g., James and Taylor 1971; James et al. 2007)

17. Discussion – Simpler Method?
Divide by the enhancement factor and use IRFs obtained from standard biokinetic model
E of 1 to 130 in the literature; which one to use?
E has a significant impact on the estimation of intake and dose; and possibly the actions taken after the intake
Large uncertainty, and should be treated as such
E of 50 would have underestimated the intake for both of the cases

18. Conclusions
Many facilities discard the data during the treatment period; and use the data “unaffected” by chelation
Maximum likelihood analysis
Use of proper biokinetic model
Bayesian analysis
Facility-specific models may be more appropriate than generic models

19. Conclusions
Pu behavior well understood; that of Pu-DTPA still largely empirical
Consensus approach needed
Literature review shows that the HP community is moving towards compartmental modeling of Pu-DTPA (e.g., Bailey et al. 2003, Fritsch et al and 2010, James et al. 2008, Breustedt et al and 2010, Konzen and Brey 2015)