title: Model-based vs hybrid iterative reconstruction technique in ultralow-dose submillisievert CT colonography.
abstract: OBJECTIVE
  To compare image quality of different reconstruction techniques in submillisievert ultralow-dose CT colonography (CTC) and to correlate colonic findings with subsequent optical colonoscopy.
  
  
  METHODS
  58 patients underwent ultralow-dose CTC. The images were reconstructed with filtered back projection (FBP), hybrid iterative reconstruction (HIR) or model-based iterative reconstruction (MBIR) techniques. In each segment, endoluminal noise (expressed as standard deviation of endoluminal density) was measured and image quality was rated on a five-point Likert scale by two independent readers. Colonic lesions were evaluated in consensus and correlated with subsequent optical colonoscopy where possible.
  
  
  RESULTS
  The estimated radiation dose was 0.41 ± 0.05 mSv for the supine and 0.42 ± 0.04 mSv for the prone acquisitions. In the endoluminal view, the image quality was rated better in HIR, whereas better scores were obtained in MBIR in the cross-sectional view, where the endoluminal noise was the lowest (p < 0.0001). Five (26%) polyps were not identified using both computer-aided detection and endoluminal inspection in FBP images vs only one (5%) in MBIR and none in HIR images.
  
  
  CONCLUSIONS
  This study showed that in submillisievert ultralow-dose CTC, the image quality for the endoluminal view is better when HIR is used, whereas MBIR yields superior images for the cross-sectional view. The inferior quality of images reconstructed with FBP may result in decreased detection of colonic lesions.
  
  
  CONCLUSIONS
  Radiation dose from CTC can be safely reduced <1 mSv for both positions when iterative reconstruction is used. MBIR provides better image quality in the cross-sectional view and HIR in the endoluminal view.
authors.affiliation: 1 Department of Radiology, First Faculty of Medicine of Charles University in Prague, Prague, Czech Republic.
authors.forename: L
authors.initials: L
authors.lastname: Lambert
authors.forename: P
authors.initials: P
authors.lastname: Ourednicek
authors.forename: J
authors.initials: J
authors.lastname: Jahoda
authors.forename: A
authors.initials: A
authors.lastname: Lambertova
authors.forename: J
authors.initials: J
authors.lastname: Danes
mesh_terms: D000368:Aged; D023881:Colonography, Computed Tomographic / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*