Fetal Dose Reduction in CT Pulmonary Angiography Using Internal Barium Shielding: A Monte Carlo Simulation Study

CT pulmonary angiography (CTPA) is a key diagnostic tool for embolic pulmonary disease during pregnancy, despite its associated high radiation exposure. To minimize the fetal radiation dose, a new technique using internal shielding has been introduced, which reduces internal scattering. This study focuses on evaluating how barium-based internal shielding impacts the reduction of fetal organ radiation dose during CTPA. For instance, a validated GATE/GEANT4 model was used to simulate CTPA acquisition. Fetal organ doses were obtained via a simulated third trimester pregnant model (Katja). In order to simulate internal shielding, Contrast agent (CA) of different sulfate barium concentrations was incorporated in the digestive cavity of the model. Also, fetal organ doses were calculated with and without internal shielding, and levels of fetal organ dose reductions were assessed for all CA concentrations. The mean fetal organ dose for CTPA without CA was 0.71 mGy. According to results, internal shielding induces a reduction in organ dose, since fetal organ dose reductions ranged between 55.89% and 69.41% with 80% CA. Furthermore, it was observed that the more CA concentration increases, the more dose reduction increases. In addition, fetal brain dose was reduced by 55.54%, 59.67%, 61.80%, and 62.94% for CA concentrations of 20%, 40%, 60%, and 80%, respectively. Clearly, this study will help provide a better assessment of fetal dose reduction via barium shielding in CTPA.