title: Diagnostic accuracy of coronary CT angiography: comparison of filtered back projection and iterative reconstruction with different strengths.
abstract: OBJECTIVE
  To investigate the diagnostic accuracy of coronary computed tomographic (CT) angiography (CCTA) using filtered back projection (FBP) and sinogram-affirmed iterative reconstruction (SAFIRE) of different strength factors with invasive coronary angiography as the reference standard.
  
  
  METHODS
  Fifty consecutive patients (32 men and 18 women) prospectively underwent electrocardiogram-triggered CCTA on a dual-source CT system. The acquisition window was set depending on the heart rate (HR): HR of less than 60 beats per minute (bpm) at the 70% RR interval, 61 to 80 bpm at 30% to 80% RR interval, and greater than 80 bpm at 30% to 50% RR interval; 100 kV and 359 to 377 mA s for patients with a body mass index of less than 24 kg/m, and 410 to 438 mA s at 120 kV for patients with a body mass index of 24 kg/m or greater. Image data were reconstructed using both FBP and SAFIRE. Sinogram-affirmed iterative reconstruction series were reconstructed using 3 different strength factors. Two blinded observers independently assessed the image quality and image impression of each coronary segment using a 4-point scale (1, non-diagnostic; and 4, excellent). Image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were measured. Filtered back projection and all SAFIRE series were independently evaluated for coronary artery stenosis (>50%), and their diagnostic accuracy was compared with invasive coronary angiography.
  
  
  RESULTS
  Statistically significant increases in SNR and CNR were obtained when higher strength factors were used. The highest SNR and CNR were found with the highest SAFIRE strength factor of 5; however, this strength also resulted in a more unfamiliar, "plasticlike" image appearance. Imaging quality scores of FBP and different SAFIRE strengths were 3.37 ± 0.49, 3.41 ± 0.47, 3.52 ± 0.30, and 3.48 ± 0.35, respectively (P < 0.001). The diagnostic accuracies were 92.91%, 93.76%, 95.28%, and 94.94% on per-segment level, respectively (P = 0.993). A tendency toward higher diagnostic performance was observed with SAFIRE strength factor 3 on per-segment analysis, albeit without reaching statistical significance. The effective radiation dose equivalent was 5.7 ± 1.6 mSv.
  
  
  CONCLUSIONS
  Sinogram-affirmed iterative reconstruction provides significant improvements in image noise, SNR, and CNR compared with FBP, which are progressive with increasing SAFIRE strength factors. Sinogram-affirmed iterative reconstruction strength factor 3 or 5 is recommended for use with CCTA.
authors.affiliation: From the *Department of Radiology, Beijing Anzhen Hospital, Capital Medical University, Beijing, China; †Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC; ‡Siemens Healthcare China, Beijing, China; §The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Hospital, Baltimore, MD; and ∥Affiliated Hospital, Hebei United University, Hebei, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
authors.forename: U Joseph
authors.initials: UJ
authors.lastname: Schoepf
authors.forename: Runze
authors.initials: R
authors.lastname: Wu
authors.forename: John W
authors.initials: JW
authors.lastname: Nance
authors.forename: Biao
authors.initials: B
authors.lastname: Lv
authors.forename: Hua
authors.initials: H
authors.lastname: Yang
authors.forename: Fang
authors.initials: F
authors.lastname: Li
authors.forename: Dongxu
authors.initials: D
authors.lastname: Lu
authors.forename: Zhaoqi
authors.initials: Z
authors.lastname: Zhang
mesh_terms: D006328:Cardiac Catheterization; D055424:Cardiac-Gated Imaging Techniques; D017023:Coronary Angiography / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed