Ogris E
Abteilung für Nuklearmedizinische Diagnostik und Therapie, Donauspitals der Stadt Wien.
Acta Med Austriaca. 1997;24(4):150-3.
The embryonal stage in mammalians is characterized by a quick proliferation and differentiation of cells. The special features of this stage of development in all living beings is therefore an increased sensitivity for the exposure with ionizing radiation. Radiation exposure during the prenatal development can therefore lead to various impairments, which can be short-termed or long-termed, showing effects even in the postnatal period. The pattern of radiation induced effects is dependent upon the radiation dose on the one hand and upon the stage of fetal development when radiation exposure occurs on the other hand. Radiation induced effects can be growth retardation, malformations, functional impairments or death as well as increased occurrence of cancer and leukemia during childhood. The main effects of a radiation exposure in the fetal period are: 1) lethal effects for the embryo, 2) malformations and changes in growth or other functional changes, 3) mental retardation, 4) induction of malignomas including leukemia. Lethal effects can be induced experimentally in animals by relatively low radiation doses of 10 cGy, administered before or immediately after the implantation of the embryo. Malformations can be induced if the exposure occurs during the period of organogenesis especially if the radiation exposure occurs during the active stage of increased cell formation and cell differentiation of a specific organ. For many types of effects of ionizing radiation especially for the death of the embryo or fetus and for macroscopic anatomical malformation a dose-effect relationship with certain threshold doses can be supposed. This threshold dose is not smaller than 5 cGy if the exposure results from a low level radiation with low LET> Radiation exposure at the end of the organogenesis and during the following fetal period can induce growth retardation and functional disturbances, which are characterized by abnormalities in the postnatal period. Of special importance are the abnormalities of the CNS, like mental retardation particularly if the radiation exposure occurred during the interval between the 8th and 15th week of pregnancy. During that time period cell formation for the development of the frontal brain occurs. The induction of this type of abnormalities as well as of other malformations is due to non stochastic effects. A threshold dose of 5 cGy ist discussed. The induction of malignancies and leukemia as a consequence of a radiation exposure in the prenatal period is to be seen as a deterministic (non stochastic) radiation effect. The sensitivity of the fetus for these effects ist 2 to 3 times higher than that of adults.
哺乳动物的胚胎阶段以细胞的快速增殖和分化为特征。因此，所有生物在这个发育阶段的特点是对电离辐射的暴露更加敏感。产前发育期间的辐射暴露因此可能导致各种损伤，这些损伤可能是短期的或长期的，甚至在出生后阶段也会显现出影响。辐射诱导效应的模式一方面取决于辐射剂量，另一方面取决于辐射暴露发生时胎儿的发育阶段。辐射诱导效应可能是生长迟缓、畸形、功能障碍或死亡，以及儿童期癌症和白血病发生率的增加。胎儿期辐射暴露的主要影响包括：1）对胚胎的致死效应；2）畸形以及生长变化或其他功能变化；3）智力迟钝；4）诱发恶性肿瘤，包括白血病。通过在胚胎植入前或植入后立即给予相对低剂量的10 cGy辐射，可以在实验动物中诱导出致死效应。如果在器官发生期发生暴露，尤其是在特定器官细胞形成和细胞分化增加的活跃阶段发生辐射暴露，就可能诱发畸形。对于许多类型的电离辐射效应，尤其是胚胎或胎儿死亡以及宏观解剖畸形，都可以假定存在与特定阈值剂量的剂量效应关系。如果暴露是由低LET的低水平辐射引起的，这个阈值剂量不小于5 cGy。在器官发生期末期和随后的胎儿期进行辐射暴露，可诱发生长迟缓及功能障碍，其特征是在出生后出现异常。中枢神经系统的异常，如智力迟钝，尤其重要，特别是如果辐射暴露发生在怀孕第8至15周之间。在此期间，额叶脑发育的细胞形成过程发生。这种类型的异常以及其他畸形的诱发是由于非随机效应。讨论的阈值剂量为5 cGy。产前辐射暴露导致的恶性肿瘤和白血病的诱发应被视为确定性（非随机）辐射效应。胎儿对这些效应的敏感性比成年人高2至3倍。
