Abstract
The radiation exposure estimates for the atomic bomb survivors at Hiroshima and Nagasaki have evolved over the past several decades, reflecting a constant strive by the Radiation Effects Research Foundation (RERF) to provide thorough dosimetry to their cohort. Recently, a working group has introduced a new series of anatomical models, called the J45 phantom series, which improves upon those currently used at RERF through greater age resolution, sex distinction, anatomical realism, and organ dose availability. To evaluate the potential dosimetry improvements that would arise from their use in an RERF Dosimetry System, organ doses in the J45 series are evaluated here using environmental fluence data for 20 generalized survivor scenarios pulled directly from the current dosimetry system. The energy- and angle-dependent gamma and neutron fluences were converted to a source term for use in MCNP6, a modern Monte Carlo radiation transport code. Overall, the updated phantom series would be expected to provide dose improvements to several important organs, including the active marrow, colon, and stomach wall (up to 20, 20, and 15% impact on total dose, respectively). The impacts were especially significant for neutron dose estimates (up to a two-fold difference) and within organs which were unavailable in the previous phantom series. These impacts were consistent across the 20 scenarios and are potentially even greater when biological effectiveness of the neutron dose component is considered. The entirety of the dosimetry results for all organs are available as supplementary data, providing confident justification for potential future DS workflows utilizing the J45 phantom series.
Highlights
From decades of bi-national funding support, the Radiation Effects Research Foundation (RERF), and its predecessor, the Atomic Bomb Casualty Commission, have composed a detailed organ dosimetry system (DS) for the atomic bomb survivors at Hiroshima and Nagasaki, Japan
Dosimetry System 2002 (DS02) was their and most recent core dosimetry system; it improved upon Dosimetry System 1986 (DS86) in many ways, including updates to the bomb source term, height of burst, radiation cross-sections for air, terrain shielding, house shielding refinements, fluence-to-KERMA factors (KERMA—kinetic energy released in matter), activation cross-sections, and fluence validation via physical measurements (Young and Kerr 2005)
A new series of phantoms produced by a multi-institutional working group has been shown to provide multiple advantages in survivor dosimetry for the atomic bomb survivors’ cohort
Summary
From decades of bi-national funding support, the Radiation Effects Research Foundation (RERF), and its predecessor, the Atomic Bomb Casualty Commission, have composed a detailed organ dosimetry system (DS) for the atomic bomb survivors at Hiroshima and Nagasaki, Japan. At RERF, radiation dose estimation constitutes a core research aim; this is because individual organ dose estimates are needed to define the relationships between radiation exposure and late-term health effects in the cohort of atomic bomb survivors. The cohort managed by RERF remains one of the largest datasets including individualized organ dose estimates for an exposed population, with information on the atomic bomb radiation output and the subsequent transport through the environment including shielding structures, and the body on a case-by-case basis (Ozasa et al 2018). The workflow for all these methods to calculate individual survivor dose estimates is contained within their DS, which has been updated over multiple decades in a constant endeavor for improved dosimetry (Cullings et al 2017; Roesch 1987; Young and Kerr 2005)
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