In vivo quantification of ¹⁸F-FDG uptake in human placenta during early pregnancy

F-FDG is the most widely used PET radiopharmaceutical. Nevertheless, no data for F-FDG uptake in the human placenta have been reported. We recently reported on embryo dosimetry in a woman who underwent an F-FDG PET/CT scan during early pregnancy. In the present work we attempt an in vivo quantification of the F-FDG uptake by the placenta. The 27-y-old woman received 320 MBq of F-FDG for a follow-up study for Hodgkin's lymphoma and was later discovered to be pregnant (embryo age = 8 wk). Imaging started 1 h after injection. The maximum placental tissue uptake (SUVmax) was 2.5. This value was conservatively attributed to the entire placental volume, i.e., 45 mL, a value representative of the average dimensions of a normal placenta at 8 wk. On the basis of these measurements, placenta F-FDG uptake in our patient was 0.19% of the injected activity. A Monte Carlo simulation was used to derive the photon dose to the embryo from the placenta (0.022 × 10 mGy per MBq of injected F-FDG) and from the surrounding amniotic fluid (0.017 × 10 mGy MBq). This increases our previously calculated dose (3.3 × 10 mGy MBq) by only a small fraction (1.18%), which does not justify modifying the previous estimate given the overall uncertainties.