OBJECTIVE. The purpose of this study was to corroborate the relation between the esti�mated absorbed fetal dose derived from directly measured uterine doses early in the first tri�mester and the volume CT dose index (CTDIvol) for 16- and 64-MDCT of the maternal chest, abdomen, and pelvis.
MATERIALS AND METHODS. Estimated absorbed fetal dose was measured with a metal oxide semiconductor field effect transistor (MOSFET) dosimeter placed in the expect�ed uterine location in an anthropomorphic phantom of a woman and scanned with 16- and 64-MDCT units of one vendor and a 64-MDCT unit of another vendor. A trauma chest, ab�domen, and pelvis protocol and an abdomen and pelvis protocol were used. Absorbed uterine dose was measured directly from the MOSFET detector. The CTDlvol for each protocol was recorded from the scanner console. Correlation between mean uterine dose and CTDIvol was tested with a goodness of fit model.
RESULTS. The absorbed uterine dose ranged from 9.25 to 37.7 mGy. Absorbed fetal dose in the early first trimester correlated with CTDIvol in a linear regression equation. For the 16-MDCT scanner, at 130 kVp, the fetal dose was 2.091 x CTDIvol - 9.489. For the 64-MDCT scanner from the same vendor, at 120 kVp, the fetal dose was 1.113 x CTDI. + 1.773. For the 64-MDCT scanner from the other vendor, at 120 kVp, the fetal dose was 1.378 x CTDIvol -1.014. The goodness of fit results (R2) for the equations were 0.97, 0.98, and 0.99.
CONCLUSION. Estimated absorbed fetal dose during the first trimester of pregnancy is linearly associated with CTDIvol regardless of beam energy, detector configuration, and scanner manufacturer.