BIOLOGICAL EFFECTS OF WHOLE-BODY PROTON IRRADIATION
Proton beams, when directed to the eyes of Macaca mulatta at 14, 39, 185, and 750 Mev suggested an RBE rangng between one and two for iridocyclitis, erythema, and cataractogenesis. These values did not vary significantly from ones obtained by comparing 14-Mev neutrons with Co/sup 60/ gamma rays. The acute radiation syndrome associated with whole-body exposure of monkeys was difficult to simulate since accelerators that are available have beams of limited diameter and homogeneity. Consequently, a scanning technique in both the horizontal and vertical planes with respect to the beam port was used. The irradiation of 40 monkeys with 730-Mev protons was accomplished by such a technique in collaboration with the Lawrence Radiation Laboratory. Animals were exposed at dose levels of one 730-Mev proton equalling 3.89 x 10/sup -8/ rad. Probit analysis established LD/sub 50/30/ as 312 rad with the 95% confidence limits ranging between 268 and 362 rad. This LD/sub 50/30/ compares fairly well with that for bomb spectrum neutrons, 393 rad, following whole-body exposure. The calculated RBE is 1.6 as compared to 1.3. Thus, for acute exposures following near uniform whole-body protons, certain similarities to neutrons of energies peaking near 4.5 Mev are evident. When clinical observations (food and water consumption, cage activity, vomiting, diarrhea, purpura, epilation, erythema, edema, death time, and survival time) were compared with previous neutron, gamma, and bomb radiation exposures, it was apparent that 250 rad of protons is a subthreshold dose whereas 535 rad is a suprathreshold for all of the effects examined. Results of peripheral blood studies and pathologic examinations paralleled those previously reported, both in degree and type of change, following exposure to other kinds of ionizing radiation. These findings are discussed in terms of manned space efforts of the future. The proton- irradiated monkeys showed a gradual onset of lethargy, anorexia, and ataxia among survivors at 21/2 to 51/2 months postirradiation. (BBB)
- Research Organization:
- Brooks Air Force Base, Tex.
- NSA Number:
- NSA-18-011658
- OSTI ID:
- 4128123
- Journal Information:
- Aerospace Med., Vol. Vol: 34; Other Information: Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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