title: Extracting atomic numbers and electron densities from a dual source dual energy CT scanner: experiments and a simulation model.
abstract: OBJECTIVE
  Dual energy CT (DECT) imaging can provide both the electron density ρ(e) and effective atomic number Z(eff), thus facilitating tissue type identification. This paper investigates the accuracy of a dual source DECT scanner by means of measurements and simulations. Previous simulation work suggested improved Monte Carlo dose calculation accuracy when compared to single energy CT for low energy photon brachytherapy, but lacked validation. As such, we aim to validate our DECT simulation model in this work.
  
  
  METHODS
  A cylindrical phantom containing tissue mimicking inserts was scanned with a second generation dual source scanner (SOMATOM Definition FLASH) to obtain Z(eff) and ρ(e). A model of the scanner was designed in ImaSim, a CT simulation program, and was used to simulate the experiment.
  
  
  RESULTS
  Accuracy of measured Z(eff) (labelled Z) was found to vary from -10% to 10% from low to high Z tissue substitutes while the accuracy on ρ(e) from DECT was about 2.5%. Our simulation reproduced the experiments within ±5% for both Z and ρ(e).
  
  
  CONCLUSIONS
  A clinical DECT scanner was able to extract Z and ρ(e) of tissue substitutes. Our simulation tool replicates the experiments within a reasonable accuracy.
authors.affiliation: Department of Radiation Oncology (MAASTRO), Maastricht University Medical Center (MUMC), The Netherlands.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Landry
authors.forename: Brigitte
authors.initials: B
authors.lastname: Reniers
authors.forename: Patrick Vincent
authors.initials: PV
authors.lastname: Granton
authors.forename: Bart
authors.initials: B
authors.lastname: van Rooijen
authors.forename: Luc
authors.initials: L
authors.lastname: Beaulieu
authors.forename: Joachim E
authors.initials: JE
authors.lastname: Wildberger
authors.forename: Frank
authors.initials: F
authors.lastname: Verhaegen
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D004583:Electrons; D006801:Humans; D015233:Models, Statistical; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D017785:Photons; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012984:Software; D015898:Tomography Scanners, X-Ray Computed; D014057:Tomography, X-Ray Computed