Fetal Radiation Doses Low in FDG-PET Scans During Pregnancy

A small-scale study has confirmed that 18F-FDG PET scans on pregnant women deliver lower-than-expected radiation doses to the fetus. The study, published this month in theJournal of Nuclear Medicine, was led by Amol Takalkar, MD, of the LSU Health Sciences Center and the Biomedical Research Foundation of Northwest Louisiana in Schreveport.

The retrospective analysis considered five pregnant women with malignancies (two with cervical cancer, two with lymphoma, and one with lung cancer) confirmed through biopsy. All underwent PET-only (no CT) studies with a reduced 18F-FDG dose (173.9 to 340.4 MBq rather than the standard 555 MBq), with the exception of one patient whose pregnancy test was negative immediately before the procedure, who received 583.12 MBq. The patients were given vigorous hydration to minimize radiation exposure to the fetus.

Researchers reviewed six 18F-FDG PET studies (one woman had two studies done), one in early pregnancy, one in the second trimester, and three in the third trimester. The fetal dose exposure from 18F-FDG PET studies was estimated to range from 1.1 to 2.43 mGy for various trimesters in pregnancy (except for the patient in the early stage of pregnancy, in whom activity in the whole uterus was considered, and the fetal dose was estimated to be 9.04 mGy). All patients delivered healthy infants with no visible abnormalities at term.

The researchers concluded that the radiation dose from 18F-FDG PET scans was “quite low and significantly below the threshold for deterministic effects due to radiation exposure to the fetus.”

In addition, Takalkar and colleagues found that the estimated fetal radiation exposure in these five cases was slightly lower than existing estimates on fetal dose exposure, and that, if confirmed by future studies, current fetal dose estimates may need revision.