title: A comparison of the ellipsoidal and voxelized dosimetric methodologies for internal, heterogeneous radionuclide sources.
abstract: Non-human biota dosimetry has historically relied on ellipsoidal dosimetric phantoms. In 2008, the International Commission on Radiological Protection (ICRP) presented a set of ellipsoidal models representative of wildlife, including dosimetric data for homogeneously distributed internal radionuclide sources. Such data makes it possible to quickly and easily estimate radiation dose rate. Voxelized modeling, first developed for use in human medical dosimetry, utilizes advanced imaging technologies to generate realistic and detailed dosimetric phantoms. Individual organs or tissues may be segmented and dosimetric data derived for each anatomic area of interest via Monte Carlo modeling. Recently, dosimetric data derived from voxelized models has become available for organisms similar to the ICRP's Reference Animals and Plants in 2008. However, if the existing ellipsoidal models are conservative, there may be little need to employ voxel models in regulatory assessments. At the same time, existing dosimetric techniques may be inadequate to resolve recent controversies surrounding the impact of ionizing radiation exposure on wildlife. This study quantifies the difference between voxel-calculated and ellipsoid-calculated dose rates for seven radionuclides assumed to be heterogeneously distributed: (14)C, (36)Cl, (60)Co, (90)Sr, (131)I, (134)Cs, (137)Cs, and (210)Po. Generally, the two methodologies agree within a factor of two to three. Finally, this paper compares the assumptions of each dosimetric system, the conditions under which each model best applies, and the implications that our results have for the ongoing dialog surrounding wildlife dosimetry.
authors.affiliation: Colorado State University, Department of Environmental & Radiological Health Sciences, Fort Collins, CO 80523, USA. Electronic address: elizarue@rams.colostate.edu.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Ruedig
authors.affiliation: Centre for Ecology & Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, LA1 4AP, UK.
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Beresford
authors.affiliation: Oregon State University, Department of Nuclear Engineering & Radiation Health Physics, Corvallis, OR 97331, USA.
authors.forename: Mario Enrique
authors.initials: ME
authors.lastname: Gomez Fernandez
authors.affiliation: Oregon State University, Department of Nuclear Engineering & Radiation Health Physics, Corvallis, OR 97331, USA.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Higley
mesh_terms: D009010:Monte Carlo Method; D011868:Radioisotopes / Q000032:analysis*; D011874:Radiometry
chemical_list: D011868:Radioisotopes
keywords: Dosimetry; Monte Carlo; Non-human biota; Voxel phantom