Original Research Article Reproducibility of coronary artery plaque volume and composition quantification by 64-detector row coronary computed tomographic angiography: An intraobserver, interobserver, and interscan variability study Victor Y. Cheng, MD a,b * , Ryo Nakazato, MD b , Damini Dey, PhD a , Swaminatha Gurudevan, MD a , Joshua Tabak c , Matthew J. Budoff, MD d , Ronald P. Karlsberg, MD a,e , James Min, MD f , Daniel S. Berman, MD a,b a Department of Medicine, 8700 Beverly Boulevard, Taper Building Room 1258, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA; b Department of Imaging, 8700 Beverly Boulevard, Taper Building Room 1258, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA; c Johns Hopkins University, Baltimore, MD, USA; d Los Angeles Biomedical Research Institute at Harbor University of California, Los Angeles, Torrance, CA, USA; e Cardiovascular Medical Group of Beverly Hills, Beverly Hills, CA, USA and f Greenberg Division of Cardiology, Weill Medical College of Cornell University, New York Presbyterian Hospital, New York, NY, USA KEYWORDS: Computed tomography; Coronary artery plaque; Reproducibility; Serial examination BACKGROUND: Interscan variability of coronary arterial plaque volume and composition quantifi cation with coronary computed tomographic angiography (CCTA), an important attribute when consid ering CCTA as a serial modality, has not been examined. OBJECTIVE: We sought to systematically determine intraobserver and interobserver interscan reproducibility of these measures. METHODS: Two blinded, experienced readers independently evaluated proximal coronary segments on CCTAs from 30 patients who underwent 2 scans within 200 days (median, 124 days; interquartile range, 49 155 days) without experiencing an interim acute coronary event. Readers recorded number of plaques and, in plaques that met a preset minimal length criterion, quantified total, calcified plaque (CP), and noncalcified plaque (NCP) volumes and percentage of total plaque volume occupied by NCP. RESULTS: Of 89 total segments studied, 36 contained detectable plaque, and 26 met criterion for quantification. Intraobserver, interobserver, and interscan agreements for normal segments were 100%. Intraobserver interscan correlations of total, CP, and NCP volumes and percentage of NCP were excellent (r 5 0.93 0.97, P values , 0.001). Interobserver interscan correlations for all measures were also very good (r 5 0.81 0.96, P values , 0.001). Variability in plaque volume quantification was significant, exceeding 60% of the averaged paired plaque volumes in the best case scenario Conflict of interest: The authors report no conflicts of interest. This study was supported by a grant from the Lincy Foundation, Beverly Hills, CA. * Corresponding author. E mail address: victor.cheng@cshs.org Submitted April 2, 2009. Accepted for publication July 20, 2009. 1934 5925/$ see front matter Ó 2009 Society of Cardiovascular Computed Tomography. All rights reserved. doi:10.1016/j.jcct.2009.07.001 Journal of Cardiovascular Computed Tomography (2009) 3, 312 320