Relative biological effectiveness of 99mTc radiopharmaceuticals.
Relative biological effectiveness of 99mTc radiopharmaceuticals.
复制标题
99mTc 放射性药物的相对生物有效性。
作者：
Narra,VR;Sastry,KS;Goddu,SM;Howell,RW;Strand,SE;Rao,DV
以小鼠睾丸生精为实验模型，以精原细胞存活为生物学终点，研究了三种99 mTc标记化合物的放射毒性。研究的放射性药物是高锝酸盐、焦磷酸盐（99 mTc-PYP）和二磷酸氢羟孕酮（99 mTc-HDP）。99 mTcO −4、99 mTc-PYP和99 mTc-HDP在37%存活率（D37）时的平均致死剂量分别为0.70±0.06、0.84±0.13和0.59±0.08戈伊。与外照射X射线或内照射γ射线测得的D_（37）值比较，其相对生物学效应（RBE）分别为0.94±0.09，0.79±0.13和1.1±0.16。这些结果表明，99 mTc在小鼠睾丸中的放射毒性与低LET辐射基本相似（即，RBE 1.1）。为了理解这些结果，这些放射性化合物在睾丸中的分布是确定的，并与观察到的RBE值相关。器官中99 mTc放射性药物的RBE值的预期范围为0.95至1.5，取决于与DNA结合的器官活性分数。这表明，在99 mTc衰变中释放的俄歇电子在体内不会引起极端的毒性。这些结果为99 mTc作为核医学显像的放射性核素提供了进一步的支持。
The radiotoxicity of three99mTc‐labeled compounds is investigated using spermatogenesis in mouse testis as the experimental model, and spermatogonial cell survival as the biological end point. The radiopharmaceuticals studied are pertechnetate , pyrophosphate (99mTc‐PYP), and hydroxyethylene diphosphate (99mTc‐HDP). The mean lethal doses at 37% survival (D37) are 0.70±0.06, 0.84±0.13, and 0.59±0.08 Gy for99mTcO−4,99mTc‐PYP, and99mTc‐HDP, respectively. When these results are compared with theD37value obtained with external x rays or internal γ rays, the relative biological effectiveness (RBE) of these compounds are 0.94±0.09, 0.79±0.13, and 1.1±0.16, respectively. These results show that the radiotoxicity of99mTc in mouse testis is essentially similar to that of low‐LET radiations (i.e., RBE∼1). To understand these results, the distribution of these radiocompounds in the testis is determined and correlated with the observed RBE values. The expected range of RBE values for99mTc radiopharmaceuticals in organs is 0.95 to 1.5, depending on the fraction of organ activity that is bound to DNA. This suggests that the Auger electrons emitted in the decay of99mTc are not capable of causing extreme toxicityinvivo. These results provide further support for99mTc as the radionuclide of choice for imaging in nuclear medicine.