Radiation dose to the fetus from [18F]-FDG administration during the second trimester of pregnancy

Abstract

We estimated the fetal radiation dose from [18F]-FDG in a rare case of a woman who underwent a PET/CT scan during the second trimester of pregnancy. The patient, a 27-year-old female with a paraganglioma, received 181.3 MBq [18F]-FDG. From the concentrations of radioactivity measured on the images, we derived the time-integrated activity coefficients of the fetus and the placenta. The time-integrated activity coefficients of the mother’s organs were taken from the standard values of the ICRP publication 106. The final fetal dose was calculated using the 6 month pregnant model of the OLINDA/EXM software. The fetus showed an overall low and homogeneous [18F]-FDG uptake, with an average concentration of 2.41 kBq cm−3. The uptake in the placenta was generally higher (average concentration = 3.69 kBq cm−3). The estimated time-integrated activity coefficients were 0.0130 and 0.0058 Bq hr Bq−1 for the fetus and the placenta respectively. The final average dose to the fetus was 1.97 × 10−2 mGy MBq−1 (3.6 mGy in this patient who received 181.3 MBq). Therefore, the dose to the fetus from [18F]-FDG administration during the second trimester of pregnancy is low. When medically indicated, pregnancy should not be a categorical basis for withholding [18F]-FDG PET scans.

Fetal Radiation Dose from 18F-FDG in Pregnant Patients Imaged with PET, PET/CT, and PET/MR

“…All published studies of humans (7,8,13,19) and nonhumans primates (11) in late pregnancy have supported the assumption made by Stabin that the average concentrations in maternal and fetal tissues are approximately equal (12). According to the present study and the study of Takalkar et al (13), doses in late pregnancy approximately range from 0.4E-02 to 1.2E-02 mGy/MBq.…”

“…In 2 previous case reports during early pregnancy, the fraction of placental uptake was estimated to be approximately 0.20% (7,10). However, the placental contours were not visible, and an average volume was used as the placental volume.…”

“…As a consequence, an ever-increasing number of pregnant women are injected with radiopharmaceuticals (2). Fetal radiation exposure may be accidental if the pregnancy is unknown at the time of the PET scan (3)(4)(5)(6) or may be the consequence of a diagnostic workup for cancer in the mother (7)(8)(9). In both cases, knowing the fetal absorbed dose is important for correctly assessing the risk to the fetus and for putting this risk in perspective against the clinical benefit for the mother.…”

“…In both cases, knowing the fetal absorbed dose is important for correctly assessing the risk to the fetus and for putting this risk in perspective against the clinical benefit for the mother. 18 F-FDG crosses the placental barrier and accumulates in fetal tissues (3,4,7,10). Therefore, the resulting fetal self-dose can be determined only from actual in vivo data.…”

“…Dosimetry from several cases of women at different stages of pregnancy subsequently became available (3,4,7,8,13), but the results were sometimes contradictory. Two cases in early pregnancy suggested that the absorbed dose might be higher than standard values (3,4).…”