Dose evaluation for foetal computed tomography with a 320-rowunit in wide-volume mode andan 80-row unit in helical scanning mode: A phantom study

The purpose of this study was to evaluate the maternal and foetal effective doses during foetal computed tomography (CT) and to compare the radiation dose, dose profile and image noise on 80-row CT in helical scanning mode and 320-row CT in widevolume scanning mode. The radiation doses were measured using thermoluminescent dosemeters implanted at various organ sites of an anthropomorphic pregnant phantom. The foetal doses in the 320-row multi-detector CT (MDCT) and 80-row MDCT units were higher than the volume CT dose index (CTDI_vol). The dose profile in the 320-row MDCToverlapped in two places but showed no overlap in the 80-row MDCT. There were no significant differences in image noise between the two scanning modes. The foetal dose evaluation by CTDI_vol may underestimate the foetal radiation risk. When using the wide-volume mode, operators must take into account the number of scans and overlap between volumetric sections.