title: Transluminal attenuation gradient and corrected models in coronary CT angiography for determining stenosis severity: a primary study using dual-source CT.
abstract: OBJECTIVE
  To compare the incremental value of transluminal attenuation gradient (TAG), TAG with corrected contrast opacification (TAG-CCO), and TAG with exclusion of calcified coronary segments (TAG-ExC) in determining the stenosis severity of coronary arteries using coronary angiography (CAG) as the reference standard.
  
  
  METHODS
  One hundred and fifteen patients who underwent computed tomography coronary angiography (CTCA) and confirmed by coronary angiography (CAG) were included in the retrospective analysis. TAG, TAG-CCO, and TAG-ExC were calculated in 311 major epicardial coronary arteries. Changes in different TAG models were compared with corresponding stenosis severities ascertained by CAG. The diagnostic performances of TAG, TAG-CCO, TAG-ExC, and the TAG/CTCA, TAG-CCO/CTCA, and TAG-ExC/CTCA combinations over CTCA alone in evaluating stenosis severity were then analysed and compared. Furthermore, the incremental value of the TAG and the corrected models in the reclassification of CTCA-evaluated stenosis severity were calculated.
  
  
  RESULTS
  TAG, TAG-CCO, and TAG-ExC decreased gradually with increased stenosis severity (p<0.001 for all TAG models). TAG and TAG-ExC improved the diagnostic performance over CTCA in total vessel evaluation (c statistic= 0.926 versus 0.907, p=0.018; c statistic= 0.922 versus 0.907, p=0.030, respectively), but TAG-CCO did not. Meanwhile, adding TAG to CTCA enabled a significant reclassification in calcified vessels (n=95; net reclassification improvement = 0.143, p=0.038).
  
  
  CONCLUSIONS
  TAG and TAG-ExC improved the diagnostic performance of CTCA in all vessels. Adding TAG to CTCA significantly reclassified the calcified vessels. The additional value of TAG-CCO over CTCA alone in determining the stenosis severity is limited.
authors.affiliation: Department of Radiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, 200072, China.
authors.forename: K
authors.initials: K
authors.lastname: Peng
authors.affiliation: Department of Radiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, 200072, China; Department of Radiology, Shanghai East Hospital, Tongji University of Medicine, Shanghai, 200120, China.
authors.forename: N
authors.initials: N
authors.lastname: Xu
authors.affiliation: Department of Radiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, 200072, China.
authors.forename: L
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Radiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, 200072, China.
authors.forename: F
authors.initials: F
authors.lastname: Xiao
authors.affiliation: Department of Radiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, 200072, China.
authors.forename: N
authors.initials: N
authors.lastname: Indima
authors.affiliation: Department of Radiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, 200072, China.
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Radiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, 200072, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Shen
authors.affiliation: Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, 200072, China.
authors.forename: W
authors.initials: W
authors.lastname: Peng
authors.affiliation: Department of Radiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, 200072, China. Electronic address: tgy17@126.com.
authors.forename: G
authors.initials: G
authors.lastname: Tang
mesh_terms: D017023:Coronary Angiography / Q000379:methods*; D023921:Coronary Stenosis / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed / Q000379:methods*