RADIOBIOLOGY OF LOW-ENERGY AND SHORT-LIVED ISOTOPES

一种新的辐射方式，封装的Pd-103种子源，现在正在研究中。 在治疗人类癌症和放射线方面的临床应用。 物理 这种同位素的特性对于其在永久性的用途是有吸引力的。 置入 与Au-198相比，Pd-103的低光子能量 （约21 keV）减少了不必要的辐射暴露。与I-125相比， 约60天的1/2），Pd-103的17天半衰期对应于更长的半衰期。 放射剂量的快速输送，这可能在 以快速生长动力学控制肿瘤。 很可能，使用 Pd-103将随着临床经验的积累而增加。 Pd-103可能具有较高的放射生物学效应 (RBE)Cs-137 它的RBE也可能大于I-125， 值范围为1.0-2.0。 没有关于Pd-103 RBE的数据。 我们 建议测量Pd-103相对于Cs-137的RBE， 剂量率和许多不同生长动力学的细胞系。的 将重新检查I-125的RBE，部分原因是与Pd- 103，部分原因是最近发现以前的剂量测定 错误. 具有短半衰期放射性核素的永久性植入物（例如PD-103或Au- 198)以递减的剂量率提供辐射。 放射生物学 这种时间-剂量模式的影响还没有很好地理解。 我们提出 实验研究的主题，这也有相关性， 放射性标记免疫疗法的放射生物学。 生物物理模型将是 与实验结果进行比较。

A new radiation modality, encapsulated Pd-103 seed sources, is now in clinical use in the treatment of human cancer and radiation. The physical characteristics of this isotope are attractive for its use in permanent implantation. In comparison with Au-198, the low photon energies of Pd-103 (about 21 keV) reduces unwanted radiation exposure. Compared to I-125 (t 1/2 of about 60 days), the 17 day half life of Pd-103 corresponds to a more rapid delivery of radiation dose, which may be more efficacious in controlling tumors with fast growth kinetics. It is likely that the use of Pd-103 will increase as clinical experience is accumulated. It is most probable that Pd-103 has higher radiobiological effectiveness (RBE) than Cs-137. Its RBE may also be greater than that of I-125, with values ranging from 1.0-2.0. No data exists on the RBE of Pd-103. We propose to measure the RBE of Pd-103 relative to Cs-137, for a number of dose rates and for a number of cell lines of different growth kinetics. The RBE of I-125 will be re-examined, in part for a direct comparison with Pd- 103, and in part motivated by the recent discovery of previous dosimetric errors. Permanent implants with short half life radionuclides (e.g. PD-103 or Au- 198) deliver radiation with decreasing dose rate. The radiobiological effect of such time-dose patterns is not well understood. We propose experiments to study the topic, which also have relevance to the radiobiology of radiolabelled immunotherapy. Biophysical models will be examined in comparison with experimental results.