Alpen E L, Powers-Risius P, Curtis S B, DeGuzman R
Lawrence Berkeley Laboratory, University of California, Berkeley 94720.
Radiat Res. 1993 Dec;136(3):382-91.
The potential for radiogenic neoplasia from charged-particle irradiation has been estimated using the Harderian gland of the mouse as a test system. Particles ranging in Z from Z = 1 (proton) to Z = 41 (niobium), in energy from 228 to 670A MeV, and in LET from 0.4 to 464 keV/microns were produced at the Lawrence Berkeley Laboratory BEVALAC. Expression of the tumorigenic potential of the initiated cells was enhanced by hormones from isogeneic grafts of pituitaries. The goal of the studies was to estimate the initial slope of the relationship between increased tumor prevalence at 16 months after irradiation and the dose received. Initial slopes were measured with good precision for 60Co gamma rays and the Bragg plateau beams of 228A MeV 4He ions, 600A MeV 56Fe ions, and 350A MeV 56Fe ions. The ratio of the initial slope for these ions to that of 60Co gamma rays give an estimate of the maximum RBE for radiogenic neoplasia. These values were 2.3 for the 4He ions, 40 for 600A MeV 56Fe, and 20 for 350A MeV 56Fe. In the studies reported here the prevalence of tumors as the result of pituitary isografts was not enhanced after irradiation with 56Fe ions. It remains to be seen how effective pituitary isografts are for enhancement of radiogenic neoplasia from other ions at different LET values. A risk analysis was undertaken using particle fluence rather than dose as the independent variable. This analysis provides a value for a "cross section" expressed in microns 2. This parameter expresses as the increase in proportion of mice with one or more Harderian gland tumors per unit increase in particle fluence. The plot of the cross section (risk coefficient) as a function of LET is monotonic, with no clear evidence of a maximum value of the risk coefficient for even the highest LET particle used.
已使用小鼠的哈德氏腺作为测试系统来估计带电粒子辐照导致放射性肿瘤的可能性。在劳伦斯伯克利国家实验室的BEVALAC产生了Z值范围从Z = 1（质子）到Z = 41（铌）、能量范围从228到670A MeV、传能线密度（LET）范围从0.4到464 keV/微米的粒子。来自同基因垂体移植的激素增强了起始细胞的致瘤潜力。这些研究的目的是估计辐照后16个月肿瘤患病率增加与所接受剂量之间关系的初始斜率。对于60Coγ射线以及228A MeV 4He离子、600A MeV 56Fe离子和350A MeV 56Fe离子的布拉格坪区束流，初始斜率的测量精度很高。这些离子的初始斜率与60Coγ射线初始斜率的比值给出了放射性肿瘤最大相对生物效应（RBE）的估计值。4He离子的值为2.3，600A MeV 56Fe为40，350A MeV 56Fe为20。在此处报告的研究中，56Fe离子辐照后，垂体同基因移植导致的肿瘤患病率并未增加。垂体同基因移植对于增强不同LET值的其他离子导致的放射性肿瘤的效果还有待观察。使用粒子注量而非剂量作为自变量进行了风险分析。该分析提供了一个以微米2表示的“截面”值。这个参数表示为每单位粒子注量增加时出现一个或多个哈德氏腺肿瘤的小鼠比例的增加。截面（风险系数）作为LET的函数图是单调的，即使对于所使用的最高LET粒子，也没有明显证据表明风险系数存在最大值。
