Priest N D
Br J Radiol. 1987 Jul;60(715):677-80. doi: 10.1259/0007-1285-60-715-677.
Toxicity studies using rodents have shown that the long-lived radium isotope radium 226 is about six times less toxic per unit of absorbed radiation dose to the skeleton than the short-lived isotope radium 224 with respect to the production of osteosarcoma. This difference in toxicity has been attributed to differences in the distribution of these isotopes. It has been suggested that 224Ra is more toxic than 226Ra because it decays on bone surfaces rather than within the volume of the bone mineral. However, in rodents many bone structures are small compared with the track length of the alpha particles and this explanation may be inadequate to explain the magnitude of the observed effect. Consequently, Monte Carlo calculations have been made to test the validity of the distribution-difference hypothesis. The results indicate that, for bone structures the size of those in mice, less than half of the observed difference in toxicity can be explained by considerations of the distribution of these radionuclides with respect to bone surfaces. Instead, it is suggested that the greater irradiation of trabecular than of cortical bone that is a characteristic of 224Ra is responsible for its enhanced toxicity.
使用啮齿动物进行的毒性研究表明，就骨肉瘤的产生而言，长寿命镭同位素镭226每单位吸收辐射剂量对骨骼的毒性比短寿命同位素镭224低约六倍。这种毒性差异归因于这些同位素分布的差异。有人认为，镭224比镭226毒性更大，因为它在骨表面而不是在骨矿物质体积内衰变。然而，在啮齿动物中，许多骨骼结构与α粒子的径迹长度相比很小，这种解释可能不足以解释观察到的效应的大小。因此，已经进行了蒙特卡罗计算，以检验分布差异假说的有效性。结果表明，对于小鼠骨骼结构大小而言，观察到的毒性差异中不到一半可以通过考虑这些放射性核素相对于骨表面的分布来解释。相反，有人认为，镭224的一个特征是小梁骨比皮质骨受到更大的照射，这是其毒性增强的原因。
