Radiation fields backscattered from material interfaces: I. Biological effectiveness.
Radiation fields backscattered from material interfaces: I. Biological effectiveness.
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从材料界面反向散射的辐射场：I. 生物有效性。
DOI：
10.2307/3579659
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发表时间：
1998
影响因子：
3.4
通讯作者：
I. Das
中科院分区：
文献类型：
--
作者：
D. Zellmer;J. Chapman;C. Stobbe;F. Xu;I. Das
将CHO-K1和CHO-xrs 5细胞的汇合培养物用137 Cs γ射线和200 kVp X射线照射附着于6 μ m Mylar上，邻近由聚苯乙烯、玻璃、铝、铜、锡和铅组成的散射材料。细胞核中的吸收剂量估计从测量的背散射剂量与平行板离子室与5微米的聚酯薄膜窗口和气体体积的厚度相当于约2.6微米的细胞或组织。在胰蛋白酶消化和计数后，通过克隆形成试验测量各种剂量后的细胞灭活。从至少两个独立实验合并的数据构建的存活曲线分别最佳拟合至CHO-K1和CHO-xrs 5细胞的线性二次（LQ）或线性方程。从固定细胞切片的电子显微照片估计，两种细胞系从散射表面到细胞核中线的平均距离为9.3+/-1.9微米。在这些材料附近照射细胞时观察到的生物效应的主要差异在很大程度上可以用物理剂量的差异来解释。使用LQ方程的进一步分析表明了额外的生物学效应与所涉及的机制的影响。CHO-K1细胞表现出一个小的，但一致的增加，在低剂量（α-灭活系数）的机制，从高Z材料散射的辐射。α系数的增加值表明RBE的增加，这可能与这些领域中的低能量和轨道端电子的比例较高有关。在CHO-K1细胞中产生最大单次杀伤的辐射场也通过二次（β-失活系数）机制产生较少的杀伤。相比之下，当同样照射，CHO-xrs 5细胞表现出显着较低的α系数的失活。这些细胞系中反向散射辐射的这种相反效应的机制基础尚不清楚。
Confluent cultures of CHO-K1 and CHO-xrs5 cells were irradiated attached to 6 microm Mylar with 137Cs gamma rays and 200 kVp X rays adjacent to scattering materials consisting of polystyrene, glass, aluminum, copper, tin and lead. The absorbed dose in cell nuclei was estimated from measurements of backscattered dose made with a parallel-plate ion chamber with a 5-microm Mylar window and a gas volume whose thickness was equivalent to approximately 2.6 microm of cells or tissue. Cell inactivation after various doses was measured by clonogenic assays after trypsinization and enumeration. Survival curves constructed from data pooled from at least two independent experiments were best fitted to a linear-quadratic (LQ) or a linear equation for CHO-K1 and CHO-xrs5 cells, respectively. An average distance of 9.3+/-1.9 microm from the scattering surfaces to the midline of nuclei for both the cell lines was estimated from electron micrographs of fixed cell sections. The major differences in biological effect observed when the cells were irradiated adjacent to these materials could be largely explained by the differences in the physical dose. Further analyses using the LQ equation suggested additional biological effects with implications for the mechanisms involved. CHO-K1 cells showed a small but consistent increase in the low-dose (alpha-inactivation coefficient) mechanism for both radiations scattered from high-Z material. An increased value of the alpha coefficient suggests an increase in RBE which could be associated with a higher proportion of low-energy and track-end electrons in these fields. The radiation fields which produced maximum single-hit killing in CHO-K1 cells also produced less killing by the quadratic (beta-inactivation coefficient) mechanism. In contrast, when similarly irradiated, CHO-xrs5 cells exhibited significantly lower alpha coefficients of inactivation. The mechanistic basis for this opposite effect of backscattered radiations in these cell lines is as yet unknown.
影响因子：
3.4
作者：
Cornforth,MN;Schillaci,ME;Goodhead,DT;Carpenter,SG;Wilder,ME;Sebring,RJ;Raju,MR
通讯作者：
Raju,MR
硫酸钡-培养基界面的物理和生物剂量测定。
DOI：
10.1259/0007-1285-59-707-1131
发表时间：
1986
期刊：
The British journal of radiology
影响因子：
--
作者：
Tokita,N;vanderKogel,I;Chmielewski,JJ;Raju,MR
通讯作者：
Raju,MR