Answer to Question #2164 Submitted to "Ask the Experts"

Q

My friend is three months pregnant. She was having problems with her kidneys at the beginning of the pregnancy and the doctor wanted her to have a CT scan and an x ray done. Now her doctor is concerned about how much radiation was absorbed and is concerned about the baby. She is not getting direct answers; could you please help?

A

With some additional information from the individual asking the question, I was able to learn that the CT scan was only of the kidneys as was the follow-up x-ray exam. The individual also estimated that the pregnancy was at one week at the time of exposure. Based on this information, the embryo received minimal or no exposure from the x rays.

Generally, for internal portions of the body to receive significant exposures, they need to be in the primary x-ray beam. In this case, the embryo was not in the primary beam, and the only possible exposure to the embryo would be from internal scatter radiation.

Internal scatter radiation is primary radiation that is scattered in all directions. It occurs when radiation interacts with tissues in the beam. Although much of that primary radiation is scattered and absorbed, some of the x rays continue to travel through the body to expose the x-ray film.

Considering the location of the embryo at one week, the amount of tissue that internal scatter radiation would have had to pass through to expose the embryo, and the low energy of the scatter radiation, it is not likely the embryo was exposed to any measurable scatter.

Kelly Classic
Certified Medical Health Physicist