title: Acute biological effects of simulating the whole-body radiation dose distribution from a solar particle event using a porcine model.
abstract: In a solar particle event (SPE), an unshielded astronaut would receive proton radiation with an energy profile that produces a highly inhomogeneous dose distribution (skin receiving a greater dose than internal organs). The novel concept of using megavoltage electron-beam radiation to more accurately reproduce both the total dose and the dose distribution of SPE protons and make meaningful RBE comparisons between protons and conventional radiation has been described previously. Here, Yucatan minipigs were used to determine the effects of a superficial, SPE-like proton dose distribution using megavoltage electrons. In these experiments, dose-dependent increases in skin pigmentation, ulceration, keratinocyte necrosis and pigment incontinence were observed. Five of 18 animals (one each exposed to 7.5 Gy and 12.5 Gy radiation and three exposed to 25 Gy radiation) developed symptomatic, radiation-associated pneumonopathy approximately 90 days postirradiation. The three animals from the highest dose group showed evidence of mycoplasmal pneumonia along with radiation pneumonitis. Moreover, delayed-type hypersensitivity was found to be altered, suggesting that superficial irradiation of the skin with ionizing radiation might cause immune dysfunction or dysregulation. In conclusion, using total doses, patterns of dose distribution, and dose rates that are compatible with potential astronaut exposure to SPE radiation, animals experienced significant toxicities that were qualitatively different from toxicities previously reported in pigs for homogeneously delivered radiation at similar doses.
authors.affiliation: University of Pennsylvania, Department of Radiation Oncology, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Jolaine M
authors.initials: JM
authors.lastname: Wilson
authors.forename: Jenine K
authors.initials: JK
authors.lastname: Sanzari
authors.forename: Eric S
authors.initials: ES
authors.lastname: Diffenderfer
authors.forename: Stephanie S
authors.initials: SS
authors.lastname: Yee
authors.forename: John T
authors.initials: JT
authors.lastname: Seykora
authors.forename: Casey
authors.initials: C
authors.lastname: Maks
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Ware
authors.forename: Harold I
authors.initials: HI
authors.lastname: Litt
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Reetz
authors.forename: James
authors.initials: J
authors.lastname: McDonough
authors.forename: Drew
authors.initials: D
authors.lastname: Weissman
authors.forename: Ann R
authors.initials: AR
authors.lastname: Kennedy
authors.forename: Keith A
authors.initials: KA
authors.lastname: Cengel
mesh_terms: D000818:Animals; D004307:Dose-Response Relationship, Radiation; D004583:Electrons / Q000009:adverse effects; D007159:Immunologic Tests; D007962:Leukocytes / Q000528:radiation effects; D023421:Models, Animal; D011874:Radiometry; D012867:Skin / Q000528:radiation effects; D019445:Solar Activity; D013552:Swine; D014916:Whole-Body Irradiation / Q000009:adverse effects; D013026:Space Flight