Estimation of fetal absorbed dose from low-dose attenuation-correction CT in PET / CT imaging by using the Body Builder Phantom

One of the methods of studying the physiology and metabolism of important tissues such as the heart, brain and cancer tumors is the use of PET/CT System. A small number of patients are pregnant women who undergo a PET/CT scan due to lack of knowledge about pregnancy or due to dire clinical need. The final dose received by the fetus is based on three factors: the absorbed dose of the fetal tissue due to radiopharmaceuticals absorption, the maternal tissue doses resulting from the absorption of radiopharmaceuticals in the mother's body, and the dose received from the CT scan. Overall, it is necessary to evaluate doses in order to minimize damage to the fetal nervous system. In this paper, using the pregnant woman's Body Builder Computed Phantom and the MCNPX computational code, the absorbed doses received from the CT component of Biograph 6(20-345mA, 80,110, 130 kV), used for attenuation correction of PET images, was calculated to be 4.5, 9.2, 13 (mGy/100mAs) for the first trimester, second trimester and third trimester of pregnancy, respectively, and according to ICRP recommendations No. 103, this range of doses should be considered for the fetus. Using the results of this study, feasibility of assessing doses to embryos in pregnant women in nuclear medicine centers is possible. The results also showed that using the Builder Body Phantom, it is possible to evaluate the fetal doses during pregnancy during CT imaging.