Abstract
1563
Purpose: It is rare that positron emission tomography/computed tomography (PET-CT) with an 18F-2-fluoro-2-deoxy-D-glucose injection (FDG) is used for pregnant patients. However, occasionally it is necessary to perform FDG PET scans in pregnant patients for staging and response evaluation. Data from literature has shown that fetal absorbed dose from FDG administration alone to pregnant patients using a MIRD approach for early, 3,6, and 9 months is 0.81, 0.81, 0.63, 0.63 mGy/mCi, respectively. However, these figures 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 mothers who underwent PET-CT scans.[1,2,3,4]
Methods: There were 14 PET-CT scans of pregnant patients obtained between 2003-2014 who were approximately 3, 6, 9 months pregnant and post-partum. The CT dose was estimated by taking the fraction of the dose along the length of the fetus divided by the dose over the entire length. The patients were scanned with a technique of 130 kVp and 30-50 mA. Each pregnant patient received 3 mCi of FDG. The dose from the PET scan was calculated using a MIRD approach with S-factors from Stabin et al.[5] column 0.5 MeV for F-18 for patients pregnant at 3, 6, 9 months and post-partum.
Results: For pregnant patients at 3, 6, 9 months and post-partum the mean PET-CT dose (mGy) to the fetus (and uterus for post-partum) with standard deviation is 1.3 ± 0.049, 0.94 ± 0.062, 0.77 ± 0.082, and 6.60 ± 0.082 mGy, respectively. The covariances are 0.19, 0.41, 0.88 and 0.10 %, respectively. For pregnant patients at 3, 6, 9 months and post-partum the mean effective dose to the fetus (or uterus for post-partum) with standard deviation is 0.016 ± 0.006, 0.021 ± 0.0070, 0.042 ± 0.041, and 0.024 ± 0.010 mSv respectively. The covariances are 0.22, 0.27, 4.01 and 0.40 %, respectively. The average fraction of 18-FDG to total dose for 3, 6, 9 months and post-partum are 0.90 ± 0.035, 0.82 ± 0.052, 0.82 ± 0.095, and 0.97 ± 0.012 mGy, respectively.
Conclusions: This study demonstrated using clinical data that fetal radiation doses and risk to fetus are consistent throughout pregnancy, thought there can be considerable intersubject variability. The total absorbed dose is well below the threshold for noncancer health effects throughout pregnancy.