title: Repeatability of in vivo quantification of atherosclerotic carotid artery plaque components by supervised multispectral classification.
abstract: OBJECTIVE
  To evaluate the agreement and scan-rescan repeatability of automated and manual plaque segmentation for the quantification of in vivo carotid artery plaque components from multi-contrast MRI.
  
  
  METHODS
  Twenty-three patients with 30-70% stenosis underwent two 3T MR carotid vessel wall exams within a 1 month interval. T1w, T2w, PDw and TOF images were acquired around the region of maximum vessel narrowing. Manual delineation of the vessel wall and plaque components (lipid, calcification, loose matrix) by an experienced observer provided the reference standard for training and evaluation of an automated plaque classifier. Areas of different plaque components and fibrous tissue were quantified and compared between segmentation methods and scan sessions.
  
  
  RESULTS
  In total, 304 slices from 23 patients were included in the segmentation experiment, in which 144 aligned slice pairs were available for repeatability analysis. The correlation between manual and automated segmented areas was 0.35 for lipid, 0.66 for calcification, 0.50 for loose matrix and 0.82 for fibrous tissue. For the comparison between scan sessions, the coefficient of repeatability of area measurement obtained by automated segmentation was lower than by manual delineation for lipid (9.9 vs. 17.1 mm(2)), loose matrix (13.8 vs. 21.2 mm(2)) and fibrous tissue (24.6 vs. 35.0 mm(2)), and was similar for calcification (20.0 vs. 17.6 mm(2)).
  
  
  CONCLUSIONS
  Application of an automated classifier for segmentation of carotid vessel wall plaque components from in vivo MRI results in improved scan-rescan repeatability compared to manual analysis.
authors.affiliation: Division of Image Processing, Department of Radiology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.
authors.forename: Shan
authors.initials: S
authors.lastname: Gao
authors.affiliation: Division of Image Processing, Department of Radiology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.
authors.forename: Ronald
authors.initials: R
authors.lastname: van 't Klooster
authors.affiliation: Department of Vascular Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Diederik F
authors.initials: DF
authors.lastname: van Wijk
authors.affiliation: Department of Radiology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Aart J
authors.initials: AJ
authors.lastname: Nederveen
authors.affiliation: Division of Image Processing, Department of Radiology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.
authors.forename: Boudewijn P F
authors.initials: BP
authors.lastname: Lelieveldt
authors.affiliation: Division of Image Processing, Department of Radiology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands. R.J.van_der_Geest@lumc.nl.
authors.forename: Rob J
authors.initials: RJ
authors.lastname: van der Geest
mesh_terms: D000368:Aged; D001331:Automation; D016893:Carotid Stenosis / Q000145:classification*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D058226:Plaque, Atherosclerotic / Q000145:classification*; D015203:Reproducibility of Results
keywords: Atherosclerotic plaque; Cardiovascular disease; Carotid artery; Classification; Multi-contrast MRI; Repeatability