Worgul B V, Brenner D J, Medvedovsky C, Merriam G R, Huang Y
Eye Radiation and Environmental Research Laboratory, Columbia University, New York, New York 10032.
Invest Ophthalmol Vis Sci. 1993 Jan;34(1):184-93.
To determine the cataractogenic potential dose of high velocity iron ions as a fixation of dose administered singly or fractionated. The dose is critical to risk assessment and to theories of radiation action and cataractogenesis.
Twenty-eight-day-old rats were examined by slit-lamp biomicroscopy on a weekly-bi-weekly basis for more than 2 yr after radiation exposure. For the acute exposure study doses of 1, 2, 5, 25, and 50 cGy were evaluated. The fractionated regimens involved total doses of 2, 25, and 50 cGy. The reference radiation consisted of 50, 100, 200, or 700 cGy of 250 kilovolt (peak) x-rays.
In accordance with previous findings in the rat using 570 MeV/amu 40Ar ions, the relative biologic effectiveness increased rapidly with decreasing dose, reaching values as high as 100. Unlike 40Ar ions, fractionation of the 56Fe doses did not produce a consistent enhancement at any of the doses examined.
The data support the previous findings of a high cataractogenic potential for high linear energy transfer (LET) radiation. The effectiveness for the production of cataracts increases with decreasing dose relative to x-rays and is independent of dose protraction. Although the present study did not reveal a consistent enhancement of effect when the ions were applied in fractions, the results are consistent with at least one theory of the inverse dose-rate effect observed for high-LET radiation.
确定高速铁离子致白内障的潜在剂量，此剂量以单次或分次给药的形式确定。该剂量对于风险评估以及辐射作用和白内障形成理论至关重要。
对28日龄大鼠在辐射暴露后2年多的时间里，每周或每两周通过裂隙灯生物显微镜进行检查。在急性暴露研究中，评估了1、2、5、25和50 cGy的剂量。分次照射方案涉及的总剂量为2、25和50 cGy。参考辐射由50、100、200或700 cGy的250千伏（峰值）X射线组成。
与先前在大鼠中使用570 MeV/amu 40Ar离子的研究结果一致，相对生物效应随剂量降低而迅速增加，高达100。与40Ar离子不同，56Fe剂量的分次照射在任何检查剂量下均未产生一致的增强效果。
数据支持先前关于高线性能量传递（LET）辐射具有高致白内障潜力的研究结果。相对于X射线，产生白内障的有效性随剂量降低而增加，且与剂量延长无关。尽管本研究未发现离子分次应用时效应有一致增强，但结果至少与高LET辐射中观察到的逆剂量率效应的一种理论相符。
