title: Abdominal CT during pregnancy: a phantom study on the effect of patient centring on conceptus radiation dose and image quality.
abstract: OBJECTIVE
  To investigate the effect of patient centring on conceptus radiation dose and image quality in abdominal CT during pregnancy.
  
  
  METHODS
  Three anthropomorphic phantoms that represent a pregnant woman at the three trimesters of gestation were subjected to a routine abdominal CT. Examinations were performed with fixed mAs (mAsf) and with the automatic exposure control system (AEC) activated. The percent reduction between mAsf and modulated mAs (mAsmod) was calculated. Conceptus dose (Dc) was measured using thermoluminencent dosimeters. To study the effect of misplacement of pregnant women on Dc, each phantom was positioned at various locations relative to gantry isocentre. Image quality was evaluated on the basis of image noise, signal-to-noise ratio, and contrast-to-noise ratio.
  
  
  RESULTS
  The maximum reduction between mAsf and mAsmod was 59.8 %, while the corresponding DC reduction was 59.3 %. DC was found to decrease by up to 25 % and 7.9 % for phantom locations below and above the isocentre, respectively. Image quality deteriorated when AEC was activated, and it was progressively improved from lower to higher than the isocentre locations.
  
  
  CONCLUSIONS
  Centring errors do not result in an increase in Dc. To maintain image quality, accurate centring is required.
  
  
  CONCLUSIONS
  • AEC activation reduces conceptus radiation dose at all gestational stages. • Patients should be accurately aligned at the gantry isocenter. • Patient centring deserves increased attention in clinical practice. • Pregnant patient centring errors do not considerably affect conceptus dose.
authors.affiliation: Faculty of Medicine, Department of Medical Physics, University of Crete, Heraklion, P.O. Box 2208, 71003, Crete, Greece.
authors.forename: G
authors.initials: G
authors.lastname: Solomou
authors.forename: A E
authors.initials: AE
authors.lastname: Papadakis
authors.forename: J
authors.initials: J
authors.lastname: Damilakis
mesh_terms: D003287:Contrast Media; D005260:Female; D006801:Humans; D019047:Phantoms, Imaging; D011247:Pregnancy; D011829:Radiation Dosage; D011860:Radiography, Abdominal; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media