title: Stent evaluation in low-dose coronary CT angiography: effect of different iterative reconstruction settings.
abstract: BACKGROUND
  Different iterative reconstruction (IR) techniques compensate increased noise from lower tube current-time product settings, yet the differences between IR settings remain unclear.
  
  
  OBJECTIVE
  Aim of this study was to test whether different IR settings have a clinically relevant influence on image quality and on the diagnostic accuracy of low-dose CT angiography in patients with a stent.
  
  
  METHODS
  Forty-two patients with 73 coronary stents were prospectively enrolled. Data were acquired with dual-source CT, and images were reconstructed with standard filtered back projection (FBP) and raw data-based IR with different settings (I3, I4, I5). Quantitative parameters, including CT-attenuation, noise, signal-to-noise ratio, contrast-to-noise ratio, as well as the presence of in-stent stenosis > 50% were determined. All patients had invasive angiography as reference standard.
  
  
  RESULTS
  Mean effective dose was 0.32 ± 0.02 mSv. Image noise decreased significantly compared with FBP (I3 = 29%; I4 = 38% and I5 = 45%), whereas signal-to-noise and contrast-to-noise ratios increased significantly (all IR settings P < .01). Subjective image quality was superior with all IR settings (P < .01). FBP sensitivity, specificity, positive predictive value, and negative predictive value were 83%, 71%, 36%, and 96% per stent compared with 100%, 76%, 44%, and 100%, respectively, in IR reconstructions independent of the IR setting applied.
  
  
  CONCLUSIONS
  In low-dose coronary CT angiography, higher IR settings significantly improved subjective and objective image quality but had no effect on accuracy.
authors.affiliation: Radiological Institute, Friedrich-Alexander-University-Erlangen-Nuremberg, Maximiliansplatz 1, 91054 Erlangen, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wuest
authors.forename: Matthias S
authors.initials: MS
authors.lastname: May
authors.forename: Michael
authors.initials: M
authors.lastname: Scharf
authors.forename: Christian
authors.initials: C
authors.lastname: Layritz
authors.forename: Jasmin
authors.initials: J
authors.lastname: Eisentopf
authors.forename: Dieter
authors.initials: D
authors.lastname: Ropers
authors.forename: Tobias
authors.initials: T
authors.lastname: Pflederer
authors.forename: Michael
authors.initials: M
authors.lastname: Uder
authors.forename: Stephan
authors.initials: S
authors.lastname: Achenbach
authors.forename: Michael M
authors.initials: MM
authors.lastname: Lell
mesh_terms: D000368:Aged; D000465:Algorithms; D017023:Coronary Angiography / Q000379:methods*; D023903:Coronary Restenosis / Q000000981:diagnostic imaging; D003331:Coronary Vessels / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D062645:Percutaneous Coronary Intervention / Q000009:adverse effects / Q000295:instrumentation*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D059629:Signal-To-Noise Ratio; D015607:Stents; D014057:Tomography, X-Ray Computed
keywords: Cardiac CT; Coronary stents; Iterative reconstruction; Low dose; SAFIRE