Reassessment of organ doses received by A-bomb survivors by precisely reproducing body dimensions of the Japanese in 1945
—The Results of Japan-U.S. Joint Research Have Enabled More Precise Epidemiological Surveys—
Epidemiological studies of A-bomb survivors conducted by the Radiation Effects Research Foundation (RERF) are some of the most important resources for data on the health effects of radiation. Precise estimation of the organ doses is the key issue in the studies, and the dosimetry system for estimating doses received by individual organs for each survivor has evolved and improved over the years. For further refinements to the dosimetry system, a Japan-U.S. joint project team was formed, comprising Nuclear Science and Engineering Center of JAEA, RERF, the University of Florida, and the U.S. National Cancer Institute. Members of this project team developed a new set of models of the human body (called “phantoms”) for adults, children, and pregnant women by precisely reproducing the standard body dimensions of Japanese people in 1945, modeled in detail with the latest CT images and other information. The project team also developed a method for more accurately estimating the organ doses of A-bomb survivors with these phantoms by utilizing the latest computational techniques such as PHITS, which were originated mainly by JAEA. Based on idealized conditions in hypothetical survivors, our initial comparisons of doses using the new phantoms and methods with doses derived from the current dosimetry system found that doses were generally consistent, although for some organs dose estimates could change by approximately ±15% at the maximum. The results of this work have been published in the journal "Radiation Research" as a series of three papers.