title: Coronary artery calcium: 0.5 mm slice-thickness reconstruction with adjusted attenuation threshold outperforms 3.0 mm by validating against spatially registered intravascular ultrasound with radiofrequency backscatter.
abstract: OBJECTIVE
  Coronary artery calcium (CAC) images can be reconstructed with thinner slice thickness on some modern multidetector-row computed tomography scanners without additional radiation. We hypothesized that the isotropic 0.5-mm CAC reconstruction outperforms the conventional 3.0-mm reconstruction in detecting and quantifying coronary calcium, and we proposed to compare them by validating against spatially registered intravascular ultrasound with radiofrequency backscatter-virtual histology (IVUS-VH).
  
  
  METHODS
  Twenty-seven patients were enrolled, and 5976 mm of coronary arteries were analyzed. A semiautomatic software was developed to coregister CAC and IVUS-VH on a detailed slice-by-slice basis. Calcium detection and calcium volume quantification were evaluated and compared using varying calcium attenuation thresholds. Algorithms for deriving individualized optimal threshold and comparable Agatston score on the 0.5-mm reconstruction were developed.
  
  
  RESULTS
  The isotropic 0.5-mm reconstruction achieved significantly higher area under receiver-operating curve than the conventional 3.0-mm reconstruction (0.9 vs. 0.74, P < .001). Using the optimal threshold, the 0.5-mm reconstruction had higher sensitivity (0.79 vs. 0.65), specificity (0.85 vs. 0.77), positive predictive value (0.42 vs. 0.29), and negative predictive value (0.97 vs. 0.94) than the 3.0 mm. Individualized optimal threshold was significantly correlated with the image noise (r = 0.66, P < .001) in the 0.5-mm reconstruction.
  
  
  CONCLUSIONS
  By optimizing the calcium threshold, the 0.5-mm reconstruction is superior to the conventional 3.0-mm in detecting and quantifying calcium, which may improve the clinical value of CAC without additional radiation.
authors.affiliation: Department of Cardiovascular Imaging, Piedmont Heart Institute, 95 Collier Rd, Atlanta, GA 30309. Electronic address: zhen.qian@piedmont.org.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Qian
authors.affiliation: Department of Cardiovascular Imaging, Piedmont Heart Institute, 95 Collier Rd, Atlanta, GA 30309; Department of Computer Science, Georgia State University, Atlanta, Georgia.
authors.forename: Abinashi
authors.initials: A
authors.lastname: Dhungel
authors.affiliation: Atlanta Medical Center, Atlanta, Georgia.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Vazquez
authors.affiliation: Department of Computer Science, Georgia State University, Atlanta, Georgia.
authors.forename: Michael
authors.initials: M
authors.lastname: Weeks
authors.affiliation: Global Genomics Group, Richmond, Virginia.
authors.forename: Szilard
authors.initials: S
authors.lastname: Voros
authors.affiliation: Department of Cardiovascular Imaging, Piedmont Heart Institute, 95 Collier Rd, Atlanta, GA 30309.
authors.forename: Sarah
authors.initials: S
authors.lastname: Rinehart
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D019540:Area Under Curve; D002118:Calcium / Q000032:analysis*; D017023:Coronary Angiography / Q000706:statistics & numerical data*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D003331:Coronary Vessels / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000706:statistics & numerical data*; D058226:Plaque, Atherosclerotic / Q000000981:diagnostic imaging; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D018084:Ultrasonography, Interventional / Q000706:statistics & numerical data; D014584:User-Computer Interface
chemical_list: D002118:Calcium
keywords: CT reconstruction; Coronary artery calcium; IVUS; registration