Answer to Question #11187 Submitted to "Ask the Experts"

My wife accompanied her mother while she had a parathyroid scintigraphy using ^99mTc. There were five other patients having cardiac scintigraphies with ^99mTc in the same room for four hours. My wife was sitting next to her mother and about 1 m away from other patients. After the scan, my wife and mother spent the whole day together. We later learned that my wife was four or five weeks pregnant during this scan. Is it possible to calculate the dose to the embryo?

Thank you for coming to the Health Physics Society "Ask the Expert" website to get some additional information on radiation exposure during early pregnancy. I trust that you shared these concerns with your doctor. This inadvertent exposure of the embryo to radiation understandably can cause some fear and uncertainty. There is a slightly increased exposure to radiation when sitting near one or more persons for a whole day who are having nuclear medicine procedures like parathyroid scintigraphy. The exposure is slightly more than what is thought of as "background." Background radiation is what we receive day to day just living here on the naturally radioactive planet Earth.

Your wife was probably exposed to something on the order of an extra five days of background. The good news: At this very low exposure there is no evidence of deleterious effects such as birth defects or cancer. In fact, up until the eighth week of pregnancy, early embryonic development is not affected by birth defects, pregnancy loss, or growth retardation unless the exposure is substantially higher.

I hope this information alleviates worry and allows you to enjoy this special time with your wife and family.

Dawn Banghart, CHP