Quantitative Assessment of the Cataractogenic Potential of Very Low Doses of Neutrons

We report on the prevalence and relative biological effectiveness (RBE) for various stages of lens opacification in rats induced by very low doses (2 to 250 mGy) of medium-energy (440 keV) neutrons, compared to those for X rays. Neutron doses were delivered either in a single fraction or in four sep...

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Bibliographic Details
Published in:Radiation research 1996-03, Vol.145 (3), p.343-349
Main Authors: Worgul, Basil V., Medvedovsky, Cecily, Huang, Youping, Marino, Stephen A., Randers-Pehrson, Gerhard, Brenner, David J.
Format: Article
Language:English
Subjects:
Aerospace Medicine
Animals
Atomic bombs
Biological and medical sciences
Biological effects of radiation
Cataract - etiology
Cataract - physiopathology
Cataracts
Dosage
Dose fractionation
Dose-Response Relationship, Radiation
Dosimetry
Fundamental and applied biological sciences. Psychology
Ionizing radiations
Lens diseases
Lens, Crystalline - radiation effects
Medical sciences
Neutrons
Ophthalmology
Probability
Radiation dosage
Radiation Injuries, Experimental
Radiotherapy
Rats
Rats, Inbred Strains
Relative biological effectiveness
Solar X rays
Time Factors
Tissues, organs and organisms biophysics
X-Rays
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Summary:We report on the prevalence and relative biological effectiveness (RBE) for various stages of lens opacification in rats induced by very low doses (2 to 250 mGy) of medium-energy (440 keV) neutrons, compared to those for X rays. Neutron doses were delivered either in a single fraction or in four separate fractions and the irradiated animals were followed for over 100 weeks. At the highest observed dose (250 mGy) and at early observation times, there was evidence of an inverse dose-rate effect; i.e., a fractionated exposure was more potent than a single exposure. Neutron RBEs relative to X rays were estimated using a non-parametric technique. The results were only weakly dependent on time postirradiation. At 30 weeks, for example, 80% confidence intervals for the RBE of acutely delivered neutrons relative to X rays were 8-16 at 250 mGy, 10-20 at 50 mGy, 50-100 at 10 mGy and 250-500 at 2 mGy. The results are consistent with the estimated neutron RBEs in Japanese A-bomb survivors, though broad confidence bounds are present in the Japanese results. Our findings are also consistent with data reported earlier for cataractogenesis induced by heavy ions in rats, mice and rabbits. We conclude from these results that, at very low doses (
ISSN:0033-7587
1938-5404
DOI:10.2307/3578991