title: Classification of noncalcified coronary atherosclerotic plaque components on CT coronary angiography: impact of vascular attenuation and density thresholds.
abstract: OBJECTIVE
  The authors assessed the effect of vascular attenuation and density thresholds on the classification of noncalcified plaque by computed tomography coronary angiography (CTCA).
  
  
  METHODS
  Thirty patients (men 25; age 59 ± 8 years) with stable angina underwent arterial and delayed CTCA. At sites of atherosclerotic plaque, attenuation values (HU) were measured within the coronary lumen, noncalcified and calcified plaque material and the surrounding epicardial fat. Based on the measured CT attenuation values, coronary plaques were classified as lipid rich (attenuation value below the threshold) or fibrous (attenuation value above the threshold) using 30-HU, 50-HU and 70-HU density thresholds.
  
  
  RESULTS
  One hundred and sixty-seven plaques (117 mixed and 50 noncalcified) were detected and assessed. The attenuation values of mixed plaques were higher than those of exclusively noncalcified plaques in both the arterial (148.3 ± 73.1 HU vs. 106.2 ± 57.9 HU) and delayed (111.4 ± 50.5 HU vs. 64.4 ± 43.4 HU) phases (p<0.01). Using a 50-HU threshold, 12 (7.2%) plaques would be classified as lipid rich on arterial scan compared with 28 (17%) on the delayed-phase scan. Reclassification of these 16 (9.6%) plaques from fibrous to lipid rich involved 4/30 (13%) patients.
  
  
  CONCLUSIONS
  Classification of coronary plaques as lipid rich or fibrous based on absolute CT attenuation values is significantly affected by vascular attenuation and density thresholds used for the definition.
authors.affiliation: Cardiovascular Imaging, Giovanni XXIII Clinic, Monastier (TV), Italy.
authors.forename: E
authors.initials: E
authors.lastname: Maffei
authors.forename: K
authors.initials: K
authors.lastname: Nieman
authors.forename: C
authors.initials: C
authors.lastname: Martini
authors.forename: O
authors.initials: O
authors.lastname: Catalano
authors.forename: S
authors.initials: S
authors.lastname: Seitun
authors.forename: T
authors.initials: T
authors.lastname: Arcadi
authors.forename: R
authors.initials: R
authors.lastname: Malagò
authors.forename: A
authors.initials: A
authors.lastname: Rossi
authors.forename: A
authors.initials: A
authors.lastname: Clemente
authors.forename: N R
authors.initials: NR
authors.lastname: Mollet
authors.forename: F
authors.initials: F
authors.lastname: Cademartiri
mesh_terms: D000704:Analysis of Variance; D060050:Angina, Stable; D055424:Cardiac-Gated Imaging Techniques; D016009:Chi-Square Distribution; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000145:classification* / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D058226:Plaque, Atherosclerotic / Q000145:classification* / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*
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