title: Clinical application of effective atomic number for classifying non-calcified coronary plaques by dual-energy computed tomography.
abstract: Coronary computed tomography (CT) angiography allows non-invasive classification of non-calcified coronary plaques (NCCPs) based on Hounsfield unit (HU) values. This methodology, however, is somewhat limited for reliable classification of NCCPs. Therefore, we evaluated the effective atomic number (EAN) for classifying NCCPs by single-source dual-energy CT with fast tube voltage switching (SSDECT).
  
  
  
  We prospectively enrolled 18 patients undergoing both SSDECT and intravascular ultrasonography (IVUS). Monochromatic images at 70 keV and EAN images were reconstructed from SSDECT data sets. Regions of interest (ROIs) within NCCPs were placed on IVUS-matched SSDECT images, and mean HU values and EANs for soft and fibrous plaques, classified using IVUS, were compared with an unpaired t-test.
  
  
  
  We placed 96 ROIs in 29 soft plaques and 37 ROIs in 15 fibrous plaques in 12 coronary arteries of 11 patients. The mean HU value in soft plaques (58.2 ± 32.8 HU) was significantly lower than that in fibrous plaques (103.9 ± 48.3 HU) (p < 0.001). The mean EAN in soft plaques (8.7 ± 0.5) was also significantly lower than that in fibrous plaques (9.6 ± 0.5) (p < 0.0001). Area under the curve for EAN (0.91) was significantly higher than that for HU value (0.79) in receiver operating characteristic curve analysis (p = 0.046). With a cutoff EAN of 9.3, sensitivity was 90% and specificity, 87%; whereas with a cutoff HU value of 55.0 HU, sensitivity was 62% and specificity, 93%.
  
  
  
  EAN measurement by SSDECT can be clinically useful for accurately classifying soft and fibrous coronary plaques.
authors.affiliation: Department of Medicine, Tokyo Women's Medical University Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, Tokyo 116-8567, Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Nakajima
authors.affiliation: Department of Medicine, Tokyo Women's Medical University Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, Tokyo 116-8567, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ito
authors.affiliation: Department of Medicine, Tokyo Women's Medical University Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, Tokyo 116-8567, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Mitsuhashi
authors.affiliation: Department of Medicine, Tokyo Women's Medical University Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, Tokyo 116-8567, Japan. Electronic address: ykubogm@dnh.twmu.ac.jp.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kubo
authors.affiliation: Department of Medicine, Tokyo Women's Medical University Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, Tokyo 116-8567, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Matsui
authors.affiliation: Department of Radiology, Tokyo Women's Medical University Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, Tokyo 116-8567, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Tanaka
authors.affiliation: Department of Radiology, Tokyo Women's Medical University Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, Tokyo 116-8567, Japan.
authors.forename: Rika
authors.initials: R
authors.lastname: Fukui
authors.affiliation: Department of Medicine, Tokyo Women's Medical University Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, Tokyo 116-8567, Japan.
authors.forename: Hisako
authors.initials: H
authors.lastname: Omori
authors.affiliation: Department of Medicine, Tokyo Women's Medical University Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, Tokyo 116-8567, Japan. Electronic address: nakaoka.takashi@twmu.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakaoka
authors.affiliation: Department of Medicine, Tokyo Women's Medical University Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, Tokyo 116-8567, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sakura
authors.affiliation: Department of Radiology, Tokyo Women's Medical University Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, Tokyo 116-8567, Japan.
authors.forename: Eiko
authors.initials: E
authors.lastname: Ueno
authors.affiliation: Department of Radiology, Tokyo Women's Medical University Medical Center East, 2-1-10 Nishiogu, Arakawa-ku, Tokyo 116-8567, Japan.
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Machida
mesh_terms: D000328:Adult; D000368:Aged; D019540:Area Under Curve; D000072226:Computed Tomography Angiography / Q000379:methods*; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000145:classification / Q000000981:diagnostic imaging* / Q000473:pathology; D003331:Coronary Vessels / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D005355:Fibrosis; D006801:Humans; D008297:Male; D008875:Middle Aged; D058226:Plaque, Atherosclerotic; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D011829:Radiation Dosage; D000069079:Radiation Exposure; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D018084:Ultrasonography, Interventional
keywords: Acute coronary syndrome; Coronary computed tomography angiography; Dual-energy computed tomography; Effective atomic number; Hounsfield unit; Non-calcified coronary plaque; Soft plaque