title: Iterative model reconstruction: improved image quality of low-tube-voltage prospective ECG-gated coronary CT angiography images at 256-slice CT.
abstract: OBJECTIVE
  To investigate the effects of a new model-based type of iterative reconstruction (M-IR) technique, the iterative model reconstruction, on image quality of prospectively gated coronary CT angiography (CTA) acquired at low-tube-voltage.
  
  
  METHODS
  Thirty patients (16 men, 14 women; mean age 52.2 ± 13.2 years) underwent coronary CTA at 100-kVp on a 256-slice CT. Paired image sets were created using 3 types of reconstruction, i.e. filtered back projection (FBP), a hybrid type of iterative reconstruction (H-IR), and M-IR. Quantitative parameters including CT-attenuation, image noise, and contrast-to-noise ratio (CNR) were measured. The visual image quality, i.e. graininess, beam-hardening, vessel sharpness, and overall image quality, was scored on a 5-point scale. Lastly, coronary artery segments were evaluated using a 4-point scale to investigate the assessability of each segment.
  
  
  RESULTS
  There was no significant difference in coronary arterial CT attenuation among the 3 reconstruction methods. The mean image noise of FBP, H-IR, and M-IR images was 29.3 ± 9.6, 19.3 ± 6.9, and 12.9 ± 3.3 HU, respectively, there were significant differences for all comparison combinations among the 3 methods (p<0.01). The CNR of M-IR was significantly better than of FBP and H-IR images (13.5 ± 5.0 [FBP], 20.9 ± 8.9 [H-IR] and 39.3 ± 13.9 [M-IR]; p<0.01). The visual scores were significantly higher for M-IR than the other images (p<0.01), and 95.3% of the coronary segments imaged with M-IR were of assessable quality compared with 76.7% of FBP- and 86.9% of H-IR images.
  
  
  CONCLUSIONS
  M-IR can provide significantly improved qualitative and quantitative image quality in prospectively gated coronary CTA using a low-tube-voltage.
authors.affiliation: Department of Cardiology, MedStar Washington Hospital Center, 110 Irving Street, NW, Washington, DC 20010, United States; Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto, 860-8556, Japan. Electronic address: seisei0430@nifty.com.
authors.forename: Seitaro
authors.initials: S
authors.lastname: Oda
authors.affiliation: Department of Cardiology, MedStar Washington Hospital Center, 110 Irving Street, NW, Washington, DC 20010, United States. Electronic address: Gaby.Weissman@medstar.net.
authors.forename: Gaby
authors.initials: G
authors.lastname: Weissman
authors.affiliation: CT Clinical Science, Philips Healthcare, c595 Miner Road, Cleveland, OH 44143, United States. Electronic address: mani.vembar@philips.com.
authors.forename: Mani
authors.initials: M
authors.lastname: Vembar
authors.affiliation: Department of Cardiology, MedStar Washington Hospital Center, 110 Irving Street, NW, Washington, DC 20010, United States. Electronic address: Guy.Weigold@MedStar.net.
authors.forename: Wm Guy
authors.initials: WG
authors.lastname: Weigold
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods*; D003287:Contrast Media; D017023:Coronary Angiography / Q000379:methods*; D005260:Female; D006801:Humans; D007472:Iohexol; D008297:Male; D008875:Middle Aged; D058996:Quality Improvement; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007472:Iohexol
keywords: Coronary CT angiography; Image quality; Iterative reconstruction; Low tube voltage; Radiation dose