title: Monoenergetic reconstructions for imaging of coronary artery stents using spectral detector CT: In-vitro experience and comparison to conventional images.
abstract: OBJECTIVE
  Accurate assessment of coronary stents using non-invasive CT imaging remains challenging despite new stent materials and improvements in CT technology. Virtual monoenergetic (monoE) images reconstructed from dual energy CT acquisitions potentially decrease artifacts caused by coronary stents. A novel spectral detector technology provides monoE and conventional images simultaneously for all conducted scans. The purpose of our study was to systematically investigate the influence of different monoE reconstructions on the visualization of coronary stent lumen in comparison to conventional images.
  
  
  METHODS
  Ten different coronary stents (diameter 3.0 mm) embedded in plastic tubes filled with contrast agent (500 HU) were scanned with a 128-row spectral detector CT (IQon, Philips, 120 kV, 125 mAs). Images were reconstructed (0.67 mm slice thickness, 0.35 mm increment) with a stent-specific conventional reconstruction kernel and 6 different monoE settings (60, 70, 80, 90, 100, 150 keV). Image quality for each stent and reconstruction was quantified using established parameters: image noise (standard deviation (SD) within a standardized ROI), in-stent attenuation difference (mean attenuation difference between stented and non-stented lumen) and visible lumen diameter (mean visible diameter of the stented tube).
  
  
  RESULTS
  Image noise was significantly lower in all monoE data dets compared to conventional images (conventional: 13.41, 60 keV: 11.62, 70 keV: 11.67, 80 keV: 11.69, 90 keV: 11.71, 100 keV: 11.75, 150 keV: 11.80 HU SD; p < 0.01). The in-stent attenuation difference was significantly smaller in monoE data with higher keV levels than in conventional images (conventional: 148.18, 60 keV: 154.13 p = 0.036, 70 keV: 143.43 p = 0.109, 80 keV: 137.25 p = 0.052, 90 keV: 133.02 p = 0.043, 100 keV: 130.12 p = 0.039, 150 keV: 123.99 HU p = 0.035). The visible lumen diameter was significantly greater in monoE data with higher keV levels than in conventional images (conventional: 0.65, 60 keV: 0.68 p = 0.542, 70 keV: 0.71 p = 0.053, 80 keV: 0.74 p < 0.01, 90 keV: 0.77 p < 0.01, 100 keV: 0.82 p < 0.01, 150 keV: 0.87 mm p < 0.01).
  
  
  CONCLUSIONS
  In comparison to conventional CT images, well-established parameters for objective assessment of CT image quality for coronary stents are significantly improved by utilization of monoE reconstructions with adequate keV levels derived from data acquired on a novel spectral detector CT platform.
authors.affiliation: Department of Radiology, University Hospital of Cologne, Cologne, Germany. Electronic address: tilman.hickethier@uk-koeln.de.
authors.forename: Tilman
authors.initials: T
authors.lastname: Hickethier
authors.affiliation: Department of Radiology, University Hospital of Cologne, Cologne, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Baeßler
authors.affiliation: Department of Radiology, University Hospital of Cologne, Cologne, Germany.
authors.forename: Jan Robert
authors.initials: JR
authors.lastname: Kroeger
authors.affiliation: Department of Radiology, University Hospital of Cologne, Cologne, Germany.
authors.forename: Jonas
authors.initials: J
authors.lastname: Doerner
authors.affiliation: Clinical Science CT, Philips Germany GmbH, Hamburg, Germany.
authors.forename: Gregor
authors.initials: G
authors.lastname: Pahn
authors.affiliation: Department of Radiology, University Hospital of Cologne, Cologne, Germany.
authors.forename: David
authors.initials: D
authors.lastname: Maintz
authors.affiliation: Department III of Internal Medicine, University Hospital of Cologne, Cologne, Germany.
authors.forename: Guido
authors.initials: G
authors.lastname: Michels
authors.affiliation: Department of Radiology, University Hospital of Cologne, Cologne, Germany.
authors.forename: Alexander C
authors.initials: AC
authors.lastname: Bunck
mesh_terms: D016477:Artifacts; D000072226:Computed Tomography Angiography / Q000295:instrumentation / Q000379:methods*; D017023:Coronary Angiography / Q000295:instrumentation / Q000379:methods*; D003331:Coronary Vessels / Q000000981:diagnostic imaging*; D006801:Humans; D061330:Multidetector Computed Tomography / Q000295:instrumentation / Q000379:methods*; D062645:Percutaneous Coronary Intervention / Q000295:instrumentation*; D019047:Phantoms, Imaging; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D015607:Stents
keywords: Computed tomography; Coronary artery; DECT; Dual energy; Dual layer; SDCT; Spectral; Spectral detector; Stent