title: How to assess non-calcified plaque in CT angiography: delineation methods affect diagnostic accuracy of low-attenuation plaque by CT for lipid-core plaque in histology.
abstract: OBJECTIVE
  To compare the accuracy of two plaque delineation methods for coronary computed tomographic angiography (CTA) to identify lipid-core plaque (LCP) using histology as the reference standard.
  
  
  RESULTS
  Five ex vivo hearts were analysed by CTA and histology. LCP was defined by histology as fibroatheroma with core diameter/circumference >200 μm/>60° and cap thickness <450 μm. In CTA, plaque was manually delineated either as the difference between the inner and outer vessel walls (Method A) or as a direct tracing of plaque (Method B). Low-attenuation plaque was defined as an area with <90 Hounsfield units. Of 446 co-registered cross-sections, 55 (12%) contained LCP. In CTA, low-attenuation plaque area was larger as assessed with Method A compared with Method B (difference: 120 ± 60%). Although low-attenuation plaque was associated with the presence of LCP, the delineation Method B yielded higher diagnostic accuracy than Method A [area under the curve (AUC): 0.831 vs. 0.780, respectively, P = 0.005]. After excluding 'normal' cross-sections by CTA (n = 117), AUC for detecting LCP became similar between both methods (0.767 vs. 0.729, P = 0.07, respectively).
  
  
  CONCLUSIONS
  Low-attenuation plaque in CTA is a diagnostic tool for LCP but prone to error if plaque is defined as the area between the inner and outer vessel walls and normal cross-sections are included in the assessment.
authors.affiliation: Cardiac MR PET CT Program, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Schlett
authors.forename: Maros
authors.initials: M
authors.lastname: Ferencik
authors.forename: Csilla
authors.initials: C
authors.lastname: Celeng
authors.forename: Pál
authors.initials: P
authors.lastname: Maurovich-Horvat
authors.forename: Hans
authors.initials: H
authors.lastname: Scheffel
authors.forename: Paul
authors.initials: P
authors.lastname: Stolzmann
authors.forename: Synho
authors.initials: S
authors.lastname: Do
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Kauczor
authors.forename: Hatem
authors.initials: H
authors.lastname: Alkadhi
authors.forename: Fabian
authors.initials: F
authors.lastname: Bamberg
authors.forename: Udo
authors.initials: U
authors.lastname: Hoffmann
mesh_terms: D019540:Area Under Curve; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000473:pathology; D016027:Heart Transplantation; D006801:Humans; D007150:Immunohistochemistry; D050356:Lipid Metabolism; D058226:Plaque, Atherosclerotic / Q000000981:diagnostic imaging* / Q000473:pathology; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D012015:Reference Standards; D012680:Sensitivity and Specificity; D014019:Tissue Donors; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: (Semi)-Automated plaque assessment; Coronary computed tomographic angiography; Low-attenuation plaque; Plaque delineation techniques