Measured fetal-region dose in X-ray pelvimetry and low-dose computed tomography using a realistic pregnant phantom: a comparative study

This study evaluated fetal-region doses and dose distributions for X-ray pelvimetry (Guthmann and Martius methods) using exposure conditions from a nationwide survey in Japan and compared them with those of a low-dose computed tomography (CT) protocol using a realistic late-pregnancy phantom. A pregnancy model phantom combining an anthropomorphic phantom with a custom-made abdominal phantom was used. Real-time dosimeters were placed at 18 sites across three abdominal levels. The low-dose CT protocol showed a nearly uniform fetal-region dose distribution, whereas the X-ray methods showed heterogeneous distributions depending on beam direction and irradiation field. The reported mean fetal-region doses were 1.16 mGy for Guthmann, 4.05 mGy for Martius, 5.21 mGy for the combined X-ray examinations, and 0.69 mGy for low-dose CT. These results indicate that the low-dose CT protocol evaluated in this study produced a lower fetal-region dose than the Guthmann and Martius methods evaluated in this study.