title: Assessment of coronary artery remodelling by dual-source CT: a head-to-head comparison with intravascular ultrasound.
abstract: BACKGROUND
  While it is widely assumed that coronary CT angiography permits detection and quantification of 'positive remodelling' of coronary atherosclerotic lesions, there is a paucity of data comparing CT with established reference methods.
  
  
  OBJECTIVE
  To assess the accuracy of dual-source CT for detecting positive versus absent or negative coronary artery remodelling of coronary atherosclerotic lesions as compared with intravascular ultrasound (IVUS).
  
  
  METHODS
  The datasets were evaluated of 38 patients referred for invasive coronary angiography and in whom an IVUS study of one coronary vessel was performed. Coronary CT angiography was performed within 24 h before invasive coronary angiography. Using dual-source CT (Siemens Healthcare, Forchheim, Germany), a contrast-enhanced volume dataset was acquired (120 kV, 400 mA/rot, collimation 2×64×0.6 mm, 60-80 ml contrast agent, intravenous). IVUS was performed using a 40 MHz IVUS catheter (Atlantis, Boston Scientific Corporation, Natick, Massachusetts, USA) and motorised pullback at 0.5 mm/s. 48 corresponding non-calcified and partially calcified plaques within the coronary artery system were identified in both CT and IVUS using bifurcation points as fiducial markers. In CT datasets, multiplanar reconstructions orthogonal to the centre line of the coronary artery were rendered and cross-sectional vessel area was measured at the site of maximal narrowing as well as at a reference segment proximal to the lesion for each of the 48 plaques. The remodelling index (RI) was calculated by dividing the vessel area at the site of maximal narrowing by the area of the reference segment. Corresponding vessel areas and RIs were also determined in IVUS.
  
  
  RESULTS
  CT classified 41 plaques as positively remodelled (RI≥1.05) and seven as having either absent or negative remodelling (RI<1.05). In IVUS 29 plaques demonstrated positive remodelling, while 19 did not. Mean cross-sectional vessel areas measured by CT at the lesion and at the reference segment were 19±5 mm(2) and 17± 5 mm(2), respectively, versus 18±5 mm(2) and 17±5 mm(2) for IVUS (mean difference 1±2 mm(2) and -0.2±1 mm(2), p<0.0001 and 0.8, respectively). The mean RI in CT was significantly larger than in IVUS (1.2±0.2 vs 1.1±0.2, p<0.0001). Correlation between CT and IVUS was higher for vessel area measurements (r>0.9, p<0.0001) than for remodelling indices (r=0.7, p<0.0001) with Bland-Altman analysis showing a systematic overestimation of vessel areas and RI in CT. Interobserver agreement was moderate for CT and IVUS measurements. Receiver operating characteristic curve analysis showed that a RI of 1.1 in CT identified positively remodelled plaques in IVUS with a sensitivity of 83% and a specificity of 78% (area under the curve=0.8, 95% CI 0.7 to 1.0). Using the standard cut-off point of 1.05 to identify positively remodelled plaques in CT resulted in a sensitivity of 100%, and a specificity of 45%.
  
  
  CONCLUSIONS
  Coronary CT angiography allows analysis of coronary artery remodelling. The degree of positive remodelling is typically overestimated by CT. A threshold of 1.1 for the RI may be optimal to classify plaques as 'positively remodelled' in coronary CT angiography.
authors.affiliation: Department of Cardiology, University of Erlangen, Erlangen, Germany, UK.
authors.forename: Sören
authors.initials: S
authors.lastname: Gauss
authors.forename: Stephan
authors.initials: S
authors.lastname: Achenbach
authors.forename: Tobias
authors.initials: T
authors.lastname: Pflederer
authors.forename: Annika
authors.initials: A
authors.lastname: Schuhbäck
authors.forename: Werner G
authors.initials: WG
authors.lastname: Daniel
authors.forename: Mohamed
authors.initials: M
authors.lastname: Marwan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002114:Calcinosis / Q000000981:diagnostic imaging / Q000473:pathology; D017023:Coronary Angiography / Q000379:methods; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging / Q000473:pathology*; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D057918:Fiducial Markers; D006801:Humans; D008297:Male; D008875:Middle Aged; D058226:Plaque, Atherosclerotic / Q000473:pathology; D014057:Tomography, X-Ray Computed; D018084:Ultrasonography, Interventional