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Session: Radiopharmaceutical Imaging and Dosimetry [Return to Session]

Fetal Dose Positron Emission Tomography and Computed Tomography in Pregnant Patients

C Burton1*, F Fahey2, B Shulkin1, (1) St Jude Children's Research Hospital, Memphis, TN, (2) Children's Hospital, Boston, MA

Presentations

MO-E115-IePD-F5-3 (Monday, 7/11/2022) 1:15 PM - 1:45 PM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 5

Purpose: It is rare that positron emission tomography/computed tomography (PET/CT) is used for pregnant patients. Data from literature has shown that fetal absorbed dose were obtained from geometric anthropomorphic phantoms. Few studies have been conducted to estimate the dose to the fetus in pregnant patients due to lack of data. The aim of this study is to demonstrate the dose to fetus using clinical data from pregnant patients who underwent PET/CT scans.

Methods: There were 9 PET-CT scans of pregnant patients obtained over an 11 year period who were 12-36 weeks pregnant (gestational age). The average size-specific dose estimates (SSDE) calculated using the water-equivalent diameter for the fetus volume. The 18F-FDG fetal self-dose and total dose from other organs from PET was calculated using a MIRD approach with specific absorption factor from Stabin et al. for 0.5 MeV with initial injection of 3.5 mCi for all patients. The maximum, 95th percentile and mean sum of uptake (SUV) for the entire fetus volume was determined using HERMES software. Fetal depth was calculated from CT images.

Results: The 18F-FDG PET fetal self-dose and total dose is 0.0017-2.18 mGy and 0.0034-2.35 mGy, respectively, and decreases with increasing fetal depth. The percentage of fetal dose to total dose ranges from 50-94% and decreases as gestational age increases. The maximum SUV is 0.11-0.73 MBq-1 kg-1 and decreases with gestational age. The SSDE ranges from 1.0-2.0 mGy.

Conclusion: This is the first study where fetal doses have been determined from CT and PET images. These types of images from pregnant patients are rare. Our data indicate that the fetal radiation exposure from 18F-FDG PET and CT performed, when medically necessary, in pregnant women with cancer is low. All efforts should be made to minimize the fetal radiation exposure by modifying the protocol appropriately.

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