title: Dual-energy computed tomography imaging to determine atherosclerotic plaque composition: a prospective study with tissue validation.
abstract: BACKGROUND
  Identifying vulnerable coronary plaque with coronary CT angiography is limited by overlap between attenuation of necrotic core and fibrous plaque. Using x-rays with differing energies alters attenuation values of these components, depending on their material composition.
  
  
  OBJECTIVE
  We sought to determine whether dual-energy CT (DECT) improves plaque component discrimination compared with single-energy CT (SECT).
  
  
  METHODS
  Twenty patients underwent DECT and virtual histology intravascular ultrasound (VH-IVUS). Attenuation changes at 100 and 140 kV for each plaque component were defined, using 1088 plaque areas co-registered with VH-IVUS. Hounsfield unit thresholds that best detected necrotic core were derived for SECT (conventional attenuation values) and for DECT (using dual-energy indices, defined as difference in Hounsfield unit values at the 2 voltages/their sum). Sensitivity of SECT and DECT to detect plaque components was determined in 77 segments from 7 postmortem coronary arteries. Finally, we examined 60 plaques in vivo to determine feasibility and sensitivity of clinical DECT to detect VH-IVUS-defined necrotic core.
  
  
  RESULTS
  In contrast to conventional SECT, mean dual-energy indices of necrotic core and fibrous tissue were significantly different with minimal overlap of ranges (necrotic core, 0.007 [95% CI, -0.001 to 0.016]; fibrous tissue, 0.028 [95% CI, 0.016-0.050]; P < .0001). DECT increased diagnostic accuracy to detect necrotic core in postmortem arteries (sensitivity, 64%; specificity, 98%) compared with SECT (sensitivity, 50%; specificity, 94%). DECT sensitivity to detect necrotic core was lower when analyzed in vivo, although still better than SECT (45% vs 39%).
  
  
  CONCLUSIONS
  DECT improves the differentiation of necrotic core and fibrous plaque in ex vivo postmortem arteries. However, much of this improvement is lost when translated to in vivo imaging because of a reduction in image quality.
authors.affiliation: Division of Cardiovascular Medicine, University of Cambridge, ACCI, Hills Road, Cambridge, CB2 0QQ, UK; Papworth Hospital NHS Foundation Trust, Cambridge, CB23 3RE, UK.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Obaid
authors.affiliation: Division of Cardiovascular Medicine, University of Cambridge, ACCI, Hills Road, Cambridge, CB2 0QQ, UK; Papworth Hospital NHS Foundation Trust, Cambridge, CB23 3RE, UK.
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Calvert
authors.affiliation: Papworth Hospital NHS Foundation Trust, Cambridge, CB23 3RE, UK.
authors.forename: Deepa
authors.initials: D
authors.lastname: Gopalan
authors.affiliation: Centre for Applied Medical Statistics, University of Cambridge, Cambridge, CB2 0QQ, UK.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Parker
authors.affiliation: Papworth Hospital NHS Foundation Trust, Cambridge, CB23 3RE, UK.
authors.forename: Nick E J
authors.initials: NE
authors.lastname: West
authors.affiliation: Papworth Hospital NHS Foundation Trust, Cambridge, CB23 3RE, UK.
authors.forename: Martin
authors.initials: M
authors.lastname: Goddard
authors.affiliation: Division of Cardiovascular Medicine, University of Cambridge, ACCI, Hills Road, Cambridge, CB2 0QQ, UK.
authors.forename: James H F
authors.initials: JH
authors.lastname: Rudd
authors.affiliation: Division of Cardiovascular Medicine, University of Cambridge, ACCI, Hills Road, Cambridge, CB2 0QQ, UK. Electronic address: mrb@mole.bio.cam.ac.uk.
authors.forename: Martin R
authors.initials: MR
authors.lastname: Bennett
mesh_terms: D006801:Humans; D058226:Plaque, Atherosclerotic / Q000000981:diagnostic imaging* / Q000473:pathology; D011446:Prospective Studies; D015900:Radiography, Dual-Energy Scanned Projection; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed
keywords: Atherosclerosis; Dual-energy computed tomography; Necrotic core; Virtual histology intravascular ultrasound