title: Evaluation of heavily calcified vessels with coronary CT angiography: comparison of iterative and filtered back projection image reconstruction.
abstract: OBJECTIVE
  To prospectively compare traditional filtered back projection (FBP) and iterative image reconstruction for the evaluation of heavily calcified arteries with coronary computed tomography (CT) angiography.
  
  
  METHODS
  The study had institutional review board approval and was HIPAA compliant. Written informed consent was obtained from all patients. Fifty-five consecutive patients (35 men, 20 women; mean age, 58 years ± 12 [standard deviation]) with Agatston scores of at least 400 underwent coronary CT angiography and cardiac catheterization. Image data were reconstructed with both FBP and iterative reconstruction techniques with corresponding cardiac algorithms. Image noise and subjective image quality were compared. To objectively assess the effect of FBP and iterative reconstruction on blooming artifacts, volumes of circumscribed calcifications were measured with dedicated volume analysis software. FBP and iterative reconstruction series were independently evaluated for coronary artery stenosis greater than 50%, and their diagnostic accuracy was compared, with cardiac catheterization as the reference standard. Statistical analyses included paired t tests, Kruskal-Wallis analysis of variance, and a modified McNemar test.
  
  
  RESULTS
  Image noise measured significantly lower (P = .011-.035) with iterative reconstruction instead of FBP. Image quality was rated significantly higher (P = .031 and .042) with iterative reconstruction series than with FBP. Calcification volumes measured significantly lower (P = .019 and .026) with iterative reconstruction (44.3 mm(3) ± 64.7 and 46.2 mm(3) ± 68.8) than with FBP (54.5 mm(3) ± 69.5 and 56.3 mm(3) ± 72.5). Iterative reconstruction significantly improved some measures of per-segment diagnostic accuracy of coronary CT angiography for the detection of significant stenosis compared with FBP (accuracy: 95.9% vs 91.8%, P = .0001; specificity: 95.8% vs 91.2%, P = .0001; positive predictive value: 76.9% vs 61.1%, P = .0001).
  
  
  CONCLUSIONS
  Iterative reconstruction reduces image noise and blooming artifacts from calcifications, leading to improved diagnostic accuracy of coronary CT angiography in patients with heavily calcified coronary arteries.
authors.affiliation: Heart and Vascular Center, Medical University of South Carolina, Ashley River Tower, 25 Courtenay Dr, Charleston, SC 29425-2260, USA.
authors.forename: Matthias
authors.initials: M
authors.lastname: Renker
authors.forename: John W
authors.initials: JW
authors.lastname: Nance
authors.forename: U Joseph
authors.initials: UJ
authors.lastname: Schoepf
authors.forename: Terrence X
authors.initials: TX
authors.lastname: O'Brien
authors.forename: Peter L
authors.initials: PL
authors.lastname: Zwerner
authors.forename: Mathias
authors.initials: M
authors.lastname: Meyer
authors.forename: J Matthias
authors.initials: JM
authors.lastname: Kerl
authors.forename: Ralf W
authors.initials: RW
authors.lastname: Bauer
authors.forename: Christian
authors.initials: C
authors.lastname: Fink
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Vogl
authors.forename: Thomas
authors.initials: T
authors.lastname: Henzler
mesh_terms: D000704:Analysis of Variance; D016477:Artifacts; D002114:Calcinosis / Q000000981:diagnostic imaging*; D016009:Chi-Square Distribution; D003287:Contrast Media; D017023:Coronary Angiography / Q000379:methods*; D023921:Coronary Stenosis / Q000000981:diagnostic imaging*; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007472:Iohexol / Q000031:analogs & derivatives; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media; D007472:Iohexol; C038192:iopromide