title: First experience with monochromatic coronary computed tomography angiography from a 64-slice CT scanner with Gemstone Spectral Imaging (GSI).
abstract: BACKGROUND
  New technology combining dual-energy CT with the latest gemstone detectors for spectral imaging (GSI) can be used to synthesize monochromatic images that mimic images as if different monochromatic x-ray sources were used.
  
  
  OBJECTIVE
  The aim of the study was to evaluate the optimal combination of monochromatic image energy and adaptive statistical iterative reconstruction (ASiR) for monochromatic reconstruction of coronary CT angiography (CTA) images with the use of GSI.
  
  
  METHODS
  Twenty consecutive patients underwent coronary CTA on a GSI capable 64-slice CT scanner (Discovery CT 750 High Definition, GE Healthcare). In 7 sets of monochromatic images (60, 65, 70, 75, 80, 90, and 110 keV; each with increasing contributions of ASiR, ie, 0%, 20%, 40%, 60%, and 80%; n = 35 reconstructions per patient), signal-to-noise (aortic root) and contrast-to-noise (left main artery) ratios were assessed. Signal-to-noise ratio, contrast-to-noise ratio, and image quality (graded on a 5-point Likert scale) were assessed in all above monochromatic reconstructions and compared with the respective standard (conventional polychromatic) image.
  
  
  RESULTS
  Compared with conventional polychromatic images, reconstructions with 60 keV and 80% ASiR showed the highest improvement in contrast-to-noise (144%; P < 0.001) and signal-to-noise ratio (173%; P < 0.001). Image quality reached a plateau at 65-75 keV with 40%-60% ASiR blending, yielding a maximal image quality score improvement of 50% compared with conventional imaging (P < 0.001).
  
  
  CONCLUSIONS
  In coronary CTA with low radiation technique (mean radiation dose, 1.8 ± 0.7 mSv), GSI with monochromatic reconstructions (65-75 keV) and ASiR (40%-60%) offers significant noise reduction and image quality improvement.
authors: Department of Radiology, Cardiac Imaging, University Hospital Zurich, Ramistrasse 100, NUK C 42, CH-8091 Zurich, Switzerland.
authors: Tobias A
authors: TA
authors: Fuchs
authors: Julia
authors: J
authors: Stehli
authors: Michael
authors: M
authors: Fiechter
authors: Svetlana
authors: S
authors: Dougoud
authors: Cathérine
authors: C
authors: Gebhard
authors: Jelena R
authors: JR
authors: Ghadri
authors: Lars
authors: L
authors: Husmann
authors: Oliver
authors: O
authors: Gaemperli
authors: Philipp A
authors: PA
authors: Kaufmann
mesh_terms: D003116:Color; D017023:Coronary Angiography / Q000295:instrumentation*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D010865:Pilot Projects; D011856:Radiographic Image Enhancement / Q000295:instrumentation*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation*; D015900:Radiography, Dual-Energy Scanned Projection / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*