title: Development of computational pregnant female and fetus models and assessment of radiation dose from positron-emitting tracers.
abstract: OBJECTIVE
  Molecular imaging using PET and hybrid (PET/CT and PET/MR) modalities nowadays plays a pivotal role in the clinical setting for diagnosis and staging, treatment response monitoring, and radiation therapy treatment planning of a wide range of oncologic malignancies. The developing embryo/fetus presents a high sensitivity to ionizing radiation. Therefore, estimation of the radiation dose delivered to the embryo/fetus and pregnant patients from PET examinations to assess potential radiation risks is highly praised.
  
  
  METHODS
  We constructed eight embryo/fetus models at various gestation periods with 25 identified tissues according to reference data recommended by the ICRP publication 89 representing the anatomy of the developing embryo/fetus. The developed embryo/fetus models were integrated into realistic anthropomorphic computational phantoms of the pregnant female and used for estimating, using Monte Carlo calculations, S-values of common positron-emitting radionuclides, organ absorbed dose, and effective dose of a number of positron-emitting labeled radiotracers.
  
  
  RESULTS
  The absorbed dose is nonuniformly distributed in the fetus. The absorbed dose of the kidney and liver of the 8-week-old fetus are about 47.45 % and 44.76 % higher than the average absorbed dose of the fetal total body for all investigated radiotracers. For18F-FDG, the fetal effective doses are 2.90E-02, 3.09E-02, 1.79E-02, 1.59E-02, 1.47E-02, 1.40E-02, 1.37E-02, and 1.27E-02 mSv/MBq at the 8th, 10th, 15th, 20th, 25th, 30th, 35th, and 38th weeks of gestation, respectively.
  
  
  CONCLUSIONS
  The developed pregnant female/fetus models matching the ICRP reference data can be exploited by dedicated software packages for internal and external dose calculations. The generated S-values will be useful to produce new standardized dose estimates to pregnant patients and embryo/fetus from a variety of positron-emitting labeled radiotracers.
authors.affiliation: Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, CH-1211, Geneva, Switzerland.
authors.forename: Tianwu
authors.initials: T
authors.lastname: Xie
authors.affiliation: Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, CH-1211, Geneva, Switzerland. habib.zaidi@hcuge.ch.|Geneva Neuroscience Center, Geneva University, Geneva, Switzerland. habib.zaidi@hcuge.ch.|Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, Netherlands. habib.zaidi@hcuge.ch.|Department of Nuclear Medicine, University of Southern Denmark, DK-500, Odense, Denmark. habib.zaidi@hcuge.ch.
authors.forename: Habib
authors.initials: H
authors.lastname: Zaidi
mesh_terms: D003198:Computer Simulation; D005260:Female; D005333:Fetus / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation / Q000379:methods*; D011247:Pregnancy / Q000502:physiology*; D011296:Prenatal Diagnosis / Q000295:instrumentation*; D011829:Radiation Dosage; D000069079:Radiation Exposure / Q000032:analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014915:Whole-Body Counting / Q000379:methods*
keywords: Monte Carlo; PET; Pregnant female models; Radiation dosimetry; Simulation