title: Early first-trimester fetal radiation dose estimation in 16-MDCT without and with automated tube current modulation.
abstract: OBJECTIVE
  The objective of our study was to correlate the estimated fetal absorbed radiation dose derived by directly measured uterine doses in the early first trimester and the volume CT dose index (CTDI(vol)) for 16-MDCT of the maternal chest, abdomen, and pelvis.
  
  
  METHODS
  Estimated absorbed fetal dose was measured using a metal oxide semiconductor field effect transistor (MOSFET) dosimeter that was placed in the uterus of an adult female anthropomorphic phantom. The phantom was scanned on a 16-MDCT scanner using three protocols. The scanning parameters for protocol A (trauma) were detector configuration, 16 x 0.625 mm; pitch, 1.75:1; rotation time, 0.5 second; 140 kVp; and 340 mA. The scanning parameters for protocol B (CT angiography) were detector configuration, 16 x 1.25 mm; pitch, 1.38:1; rotation time, 0.6 second; 140 kVp; and 300 mA. The scanning parameters for protocol C, which is the automated tube current modulation (ATCM) protocol previously used in the literature, were detector configuration, 16 x 1.25 mm; pitch, 0.938:1; rotation time, 0.5 second; 140 kVp; and 380 mA. The protocols were also modified for the ATCM mode; the CTDI(vol) was documented from the scanner's console. Correlation between these data was tested with a goodness-of-fit model.
  
  
  RESULTS
  Absorbed fetal radiation dose in the early first trimester correlated with the CTDI(vol) via a linear regression equation. For a constant tube current and peak voltage of 140 kVp, fetal dose (mGy) = 1.665 x CTDI(vol) (mGy) - 7.059. For the ATCM mode and a constant kVp of 140, fetal dose (mGy) = 2.151 x CTDI(vol) (mGy) - 2.200. The goodness of fit (R(2)) for the equations is 0.99 and 0.91, respectively.
  
  
  CONCLUSIONS
  In both the manual and ATCM modes, absorbed fetal radiation dose can be estimated from the CTDI(vol) obtained at the time of scanning independent of pitch and tube current-time product (mAs).
authors: Department of Radiology, Duke University Medical Center, Erwin Rd., Box 3808, Durham, NC 27710, USA. jaffe002@mc.duke.edu
authors: Tracy A
authors: TA
authors: Jaffe
authors: Terry T
authors: TT
authors: Yoshizumi
authors: Greta I
authors: GI
authors: Toncheva
authors: Giao
authors: G
authors: Nguyen
authors: Lynne M
authors: LM
authors: Hurwitz
authors: Rendon C
authors: RC
authors: Nelson
mesh_terms: D005260:Female; D005333:Fetus / Q000528:radiation effects*; D006801:Humans; D019047:Phantoms, Imaging; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation*; D014057:Tomography, X-Ray Computed