title: Development of a 9-months pregnant hybrid phantom and its internal dosimetry for thyroid agents.
abstract: As a consequence of fetal radiosensitivity, the estimation of internal dose received by a fetus from radiopharmaceuticals applied to the mother is often important in nuclear medicine. A new 9-months pregnant phantom based on magnetic resonance (MR) images tied to the International Commission on Radiological Protection (ICRP) reference voxel phantom has been developed. Maternal and fetal organs were segmented from a set of pelvic MR images of a 9-months pregnant subject using 3D-DOCTOR(TM) and then imported into the 3D modeling software package Rhinoceros(TM) for combining with the adult female ICRP voxel phantom and further modeling. Next, the phantom organs were rescaled to match with reference masses described in ICRP Publications. The internal anatomy of previous pregnant phantom models had been limited to the fetal brain and skeleton only, but the fetus model developed in this study incorporates 20 different organs. The current reference phantom has been developed for application in comprehensive dosimetric study in nuclear medicine. The internal dosimetry calculations were performed for thyroid agents using the Monte Carlo transport method. Biokinetic data for these radiopharmaceuticals were used to estimate cumulated activity during pregnancy and maternal and fetal organ doses at seven different maximum thyroid uptake levels. Calculating the dose distribution was also presented in a sagittal view of the pregnant model utilizing the mesh tally function. The comparisons showed, in general, an overestimation of the absorbed dose to the fetus and an underestimation of the fetal thyroid dose in previous studies compared with the values based on the current hybrid phantom.
authors: Physics Department, School of Sciences, Ferdowsi University of Mashhad, Azadi Square, Mashhad, 91775-1436, Iran.
authors: E
authors: E
authors: Hoseinian-Azghadi
authors: Physics Department, School of Sciences, Ferdowsi University of Mashhad, Azadi Square, Mashhad, 91775-1436, Iran.
authors: L
authors: L
authors: Rafat-Motavalli
authors: Physics Department, School of Sciences, Ferdowsi University of Mashhad, Azadi Square, Mashhad, 91775-1436, Iran mirihakim@ferdowsi.um.ac.ir.
authors: H
authors: H
authors: Miri-Hakimabad
mesh_terms: D000328:Adult; D005260:Female; D005333:Fetus / Q000528:radiation effects*; D005865:Gestational Age; D006801:Humans; D021621:Imaging, Three-Dimensional; D007457:Iodine Radioisotopes / Q000009:adverse effects; D008279:Magnetic Resonance Imaging; D008953:Models, Anatomic; D058958:Organs at Risk / Q000528:radiation effects; D019047:Phantoms, Imaging; D011247:Pregnancy; D011874:Radiometry / Q000379:methods; D019275:Radiopharmaceuticals / Q000009:adverse effects*; D013961:Thyroid Gland / Q000528:radiation effects*
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals
keywords: hybrid phantom; internal dosimetry; pregnancy; reference phantom; thyroid agents