Witcofski R L, Smith E M, Pizzarello D J
Phys Med Biol. 1975 Mar;20(2):255-60. doi: 10.1088/0031-9155/20/2/007.
Dosimetry theory related to volume sources containing uniformly distributed beta-emitting radionuclides predicts a rapid drop in dose at the outer surface to approximately one half of the maximum dose within the volume. The purpose of this study was to determine if this reduction in surface dose could be observed using a measurable biological endpoint. In this study rats were injected with radiocolloids of either 198Au, 113In-m or 99Tc-m, to produce liver irradiation from their decay, or their livers were treated with external X-irradiation. After irradiation, a portion of the liver was surgically removed to stimulate cell division in the liver remnant revealing radiation damage in the form of chromosomal aberrations. The percentages of dividing cells with bridges were scored in the outer edges (0.45 mm) of the tissue sections and were compared to levels obtained from the central portion of the liver lobe. No significant difference was observed with X-irradiation or from 99Tc-m irradiation. However, irradiation with 198-Au and 113In-m (which emit large numbers of energetic electrons) produced significantly fewer aberrations in the outer layer when compared to the central portion. These differences in the distribution of biological damage allowed us to detect the predicted dose reduction at the surface of volume sources containing beta emitters.
与含有均匀分布的发射β射线放射性核素的体积源相关的剂量学理论预测，在体积源外表面处剂量会迅速下降至体积内最大剂量的约一半。本研究的目的是确定是否可以使用可测量的生物学终点观察到表面剂量的这种降低。在本研究中，给大鼠注射198Au、113In-m或99Tc-m的放射性胶体，以通过它们的衰变产生肝脏照射，或者对它们的肝脏进行外部X射线照射。照射后，手术切除一部分肝脏以刺激肝脏残余物中的细胞分裂，从而揭示以染色体畸变形式存在的辐射损伤。对组织切片外边缘（0.45毫米）处具有桥接的分裂细胞百分比进行评分，并与从肝叶中央部分获得的水平进行比较。X射线照射或99Tc-m照射未观察到显著差异。然而，与中央部分相比，用198Au和113In-m（发射大量高能电子）照射在外层产生的畸变明显较少。生物损伤分布的这些差异使我们能够检测到含有β发射体的体积源表面处预测的剂量降低。
