A 24-year-old woman in the first trimester of pregnancy requires imaging. Among the following investigations, the HIGHEST absorbed dose to the fetus would be delivered by:

• A Chest radiograph (PA view)
• B CT scan of the head
• C Radiograph of the ankle
• D CT scan of the abdomen and pelvis ✓

Explanation

Fetal dose depends on whether the uterus lies within or near the primary beam. An abdominal and pelvic CT delivers roughly 10 to 35 mGy to the uterus because the fetus is directly irradiated. A chest radiograph scatters less than 0.01 mGy, a limb radiograph is negligible, and a head CT contributes only scattered radiation well under 0.01 mGy. Any fetal dose below about 50 mGy is not considered an indication for termination.

Reference: Grainger and Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.