title: Evaluation of image quality and lesion perception by human readers on 3D CT colonography: comparison of standard and low radiation dose.
abstract: OBJECTIVE
  We compared the prevalence of noise-related artefacts and lesion perception on three-dimensional (3D) CT colonography (CTC) at standard and low radiation doses.
  
  
  METHODS
  Forty-eight patients underwent CTC (64 x 0.625 mm collimation; tube rotation time 0.5 s; automatic tube current modulation: standard dose 40-160 mA, low dose 10-50 mA). Low- and standard-dose acquisitions were performed in the supine position, one after the other. The presence of artefacts (cobblestone and snow artefacts, irregularly delineated folds) and the presence of polyps were evaluated by five radiologists on 3D images at standard dose, the original low dose and a modified low dose, i.e. after manipulation of opacity on 3D.
  
  
  RESULTS
  The mean effective dose was 3.9 +/- 1.3 mSv at standard dose and 1.03 +/- 0.4 mSv at low dose. The number of images showing cobblestone artefacts and irregularly delineated folds at original and modified low doses was significantly higher than at standard dose (P < 0.0001). Most of the artefacts on modified low-dose images were mild. No significant difference in sensitivity between the dose levels was found for polyps > or =6 mm.
  
  
  CONCLUSIONS
  Reduction of the effective dose to 1 mSv significantly affects image quality on 3D CTC, but the perception of > or =6 mm lesions is not significantly impaired.
authors.affiliation: Department of Radiology, Sahlgrenska University Hospital, Bruna Stråket 11, 41342 Gothenburg, Sweden. valeria.fisichella@vgregion.se
authors.forename: Valeria A
authors.initials: VA
authors.lastname: Fisichella
authors.forename: Magnus
authors.initials: M
authors.lastname: Båth
authors.forename: Ase
authors.initials: A
authors.lastname: Allansdotter Johnsson
authors.forename: Fredrik
authors.initials: F
authors.lastname: Jäderling
authors.forename: Tommy
authors.initials: T
authors.lastname: Bergsten
authors.forename: Ulf
authors.initials: U
authors.lastname: Persson
authors.forename: Kristin
authors.initials: K
authors.lastname: Mellingen
authors.forename: Mikael
authors.initials: M
authors.lastname: Hellström
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003110:Colonic Neoplasms / Q000000981:diagnostic imaging*; D023881:Colonography, Computed Tomographic / Q000379:methods*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity