MEDRADSC 3U03 Lecture Notes - Lecture 9: Microcephaly, Dosimetry, Gestational Age
4 Jan 2017
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History early 1900s reports began to appear in medical literature of mental retardation in children born in women who had received pelvic radiotherapy. It was determined that large doses of radiation were required to produce these effects. Other than cancer, devlepmental effects on the unborn child are of the greatest. Induced before or immediately after implantation of the embryo into uterine wall. Expressed in prenatal or neoneatal death: malformations. Characteristic of period of organogenesis: growth distrubances without malformations. Induced at all stages of fetal development, but particularly in latter part of pregnancy. Most sensitive stage to the lethal effects of radiation: 0. 05 to 0. 15 gy can kill a fertilized egg (not much dose) High incidence of prenatal death may be expressed as a decrease in litter size. Few (if any) abnormalities are produced (cid:862)all-or-(cid:374)othi(cid:374)g(cid:863) effe(cid:272)t of radiatio(cid:374) at this stage.
