title: Compound analysis of gallstones using dual energy computed tomography--results in a phantom model.
abstract: OBJECTIVE
  The potential of dual energy computed tomography (DECT) for the analysis of gallstone compounds was investigated. The main goal was to find parameters, that can reliably define high percentage (>70%) cholesterol stones without calcium components.
  
  
  METHODS
  35 gallstones were analyzed with DECT using a phantom model. Stone samples were put into specimen containers filled with formalin. Containers were put into a water-filled cylindrical acrylic glass phantom. DECT scans were performed using a tube voltage/current of 140 kV/83 mAs (tube A) and 80 kV/340 mAs (tube B). ROI-measurements to determine CT attenuation of each sector of the stones that had different appearance on the CT images were performed. Finally, semi-quantitative infrared spectroscopy (FTIR) of these sectors was performed for chemical analysis.
  
  
  RESULTS
  ROI-measurements were performed in 45 different sectors in 35 gallstones. Sectors containing >70% of cholesterol and no calcium component (n=20) on FTIR could be identified with 95% sensitivity and 100% specificity on DECT. These sectors showed typical attenuation of -8+/-4 HU at 80 kV and +22+/-3 HU at 140 kV. Even the presence of a small calcium component (<10%) hindered the reliable identification of cholesterol components as such.
  
  
  CONCLUSIONS
  Dual energy CT allows for reliable identification of gallstones containing a high percentage of cholesterol and no calcium component in this pre-clinical phantom model. Results from in vivo or anthropomorphic phantom trials will have to confirm these results. This may enable the identification of patients eligible for non-surgical treatment options in the future.
authors.affiliation: Department of Diagnostic and Interventional Radiology, Clinic of the Goethe University Frankfurt, Theodor-Stern-Kai 7, 60596 Frankfurt, Germany. ralfwbauer@aol.com
authors.forename: Ralf W
authors.initials: RW
authors.lastname: Bauer
authors.forename: Julian R
authors.initials: JR
authors.lastname: Schulz
authors.forename: Barbara
authors.initials: B
authors.lastname: Zedler
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Graf
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Vogl
mesh_terms: D042882:Gallstones / Q000000981:diagnostic imaging*; D006801:Humans; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015900:Radiography, Dual-Energy Scanned Projection / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*