Fetal Risk in Diagnostic Radiology

Summary of recommended annual doses and different kinds of potential biological effects. Dose limit for members of the public recommended by ICRP is 1 mSv/y, excluding natural background radiation and medical doses. In the United States, annual exposure to natural background radiation is approximately 3 mSv/y, including 2 mSv attributed to indoor radon. ICRP recommends an annual occupational dose limit of 20 mSv/y when averaged over 5 years. For pregnant workers, ICRP recommends a limit of 1 mSv from declaration of pregnancy to birth of a child. Recommendation from National Council on Radiation Protection for a declared pregnant worker is maximum of 0.5 mSv/month, which equals a total dose of 5 mSv. Radiation sickness is due to an extremely high, albeit brief, whole-body lethal dose. Severity of symptoms associated with radiation sickness increases as dose increases, ranging from nausea, vomiting, anorexia, diarrhea, hypotension, and death. LD 50/60 is the single, uniform whole-body lethal dose that would kill 50% of the irradiated human population within 60 days and is estimated to be 3-5 Sv.

Litter of a female mouse irradiated with x-rays during organogenesis and killed at 19 days. Multiple anomalies are evident. Among the 5 embryos in the top row, only the middle third is normal. Remainder of embryos demonstrate exencephaly, exencephaly and evisceration, and anencephaly (from left to right). The 4 embryos on the bottom row are resorbed.

MR image of 41-year-old man who was exposed to in utero radiation at 8-9 weeks after conception from the atomic bomb in Hiroshima. Coronal MR image demonstrates thinning of the cortical gray matter of both cerebral hemispheres as well as subependymal heterotopic gray matter nodules lining both lateral ventricles, characteristic of congenital central nervous system malformation.

Photograph of teenage survivor of the atomic bomb in Nagaski with microcephaly and growth retardation. On the right of the photograph is 15-year-old boy who was exposed to in utero radiation at approximately 7 weeks of gestation and at 1.2 km from the hypocenter. A normal 12-year-old boy is seen on the left of the photograph.

27-weeks pregnant patient with right-sided pleuritic chest pain. (A) Topogram of CT angiography of the chest demonstrates the use of oral barium sulfate (arrowhead) and lead apron (open arrow) as methods of fetal shielding. (B) Axial CT image with intravenous contrast demonstrates a segmental pulmonary embolus in the right lower lobe (arrow).