title: Fetal and maternal absorbed dose estimates for positron-emitting molecular imaging probes.
abstract: PET and hybrid (PET/CT and PET/MR) imaging currently play a pivotal role in clinical diagnosis, staging and restaging, treatment, and surveillance of several diseases. As such, limiting the radiation exposure of special patients, such as pregnant women, from PET procedures is an important challenge that needs to be appropriately addressed because of the high sensitivity of the developing embryo/fetus to ionizing radiation. Therefore, accurate radiation dose calculation for the embryo/fetus and pregnant patient from common positron-emitting radiotracers is highly desired.
  
  
  METHODS
  To obtain representative estimates of radiation dose to the human body, realistic biologic and physical models should be used. In this work, we evaluate the S values of 9 positron-emitting radionuclides ((11)C, (13)N, (15)O, (18)F, (64)Cu, (68)Ga, (82)Rb, (86)Y, and (124)I) and the absorbed and effective doses for 21 positron-emitting labeled radiotracers using realistic anthropomorphic computational phantoms of early pregnancy and at 3-, 6-, and 9-mo of gestation and the most recent biokinetic data available. The Monte Carlo N-Particle eXtended general-purpose Monte Carlo code was used for radiation transport simulation.
  
  
  RESULTS
  The absorbed dose to the pregnant model is less influenced by the gestation for most organs or tissues, but the anatomic changes of the maternal body increases the effective dose for some radiotracers. For (18)F-FDG, the estimated absorbed doses to the embryo/fetus are 3.05E-02, 2.27E-02, 1.50E-02, and 1.33E-02 mGy/MBq at early pregnancy and 3-, 6-, and 9-mo gestation, respectively. The absorbed dose is nonuniformly distributed in the fetus and would be 1.03-2 times higher in the fetal brain than in other fetal soft tissues.
  
  
  CONCLUSIONS
  The generated S values can be exploited to estimate the radiation dose delivered to pregnant patients and the embryo/fetus from various PET radiotracers used in clinical and research settings. The generated dosimetric database of radiotracers using new-generation computational models can be used for the assessment of radiation risks to pregnant women and the embryo/fetus undergoing PET/CT imaging procedures. This work also contributes to a better understanding of the absorbed dose distribution in the fetus.
authors.affiliation: Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva, Switzerland.
authors.forename: Tianwu
authors.initials: T
authors.lastname: Xie
authors.affiliation: Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva, Switzerland Geneva Neuroscience Center, Geneva University, Geneva, Switzerland; and Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands habib.zaidi@hcuge.ch.
authors.forename: Habib
authors.initials: H
authors.lastname: Zaidi
mesh_terms: D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D005260:Female; D005333:Fetus / Q000528:radiation effects*; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006801:Humans; D057054:Molecular Imaging; D010673:Pheochromocytoma / Q000000981:diagnostic imaging; D049268:Positron-Emission Tomography / Q000379:methods*; D011247:Pregnancy; D011829:Radiation Dosage
chemical_list: D019788:Fluorodeoxyglucose F18; C043437:fluorodopa F 18; D004295:Dihydroxyphenylalanine
keywords: Monte Carlo; PET; pregnant female model; radiation dosimetry; simulation