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Bragg Curve, Biological Bragg Curve and Biological Issues in Space Radiation Protection with ShieldingThe space environment consists of a varying field of radiation particles including high-energy ions, with spacecraft shielding material providing the major protection to astronauts from harmful exposure. Unlike low-LET gamma or X-rays, the presence of shielding does not always reduce the radiation risks for energetic charged particle exposure. Since the dose delivered by the charged particle increases sharply as the particle approaches the end of its range, a position known as the Bragg peak, the Bragg curve does not necessarily represent the biological damage along the particle traversal since biological effects are influenced by the track structure of both primary and secondary particles. Therefore, the biological Bragg curve is dependent on the energy and the type of the primary particle, and may vary for different biological endpoints. To achieve a Bragg curve distribution, we exposed cells to energetic heavy ions with the beam geometry parallel to a monolayer of fibroblasts. Qualitative analyses of gamma-H2AX fluorescence, a known marker of DSBs, indicated increased clustering of DNA damage before the Bragg peak, enhanced homogenous distribution at the peak, and provided visual evidence of high linear energy transfer (LET) particle traversal of cells beyond the Bragg peak. A quantitative biological response curve generated for micronuclei (MN) induction across the Bragg curve did not reveal an increased yield of MN at the location of the Bragg peak. However, the ratio of mono-to bi-nucleated cells, which indicates inhibition in cell progression, increased at the Bragg peak location. These results, along with other biological concerns, show that space radiation protection with shielding can be a complicated issue.
Document ID
20080029277
Acquisition Source
Johnson Space Center
Document Type
Conference Proceedings
Authors
Honglu, Wu
(NASA Johnson Space Center Houston, TX, United States)
Cucinotta, F.A.
(NASA Johnson Space Center Houston, TX, United States)
Durante, M.
Lin, Z.
Rusek, A.
Date Acquired
August 24, 2013
Publication Date
July 23, 2006
Subject Category
Aerospace Medicine
Report/Patent Number
JSC-CN-9980
Meeting Information
Meeting: Committee on Space Research (COSPAR) Colloquium
Location: Xian
Country: China
Start Date: July 23, 2006
End Date: July 25, 2006
Distribution Limits
Public
Copyright
Other

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