title: Fast analytical scatter estimation using graphics processing units.
abstract: OBJECTIVE
  To develop a fast patient-specific analytical estimator of first-order Compton and Rayleigh scatter in cone-beam computed tomography, implemented using graphics processing units.
  
  
  METHODS
  The authors developed an analytical estimator for first-order Compton and Rayleigh scatter in a cone-beam computed tomography geometry. The estimator was coded using NVIDIA's CUDA environment for execution on an NVIDIA graphics processing unit. Performance of the analytical estimator was validated by comparison with high-count Monte Carlo simulations for two different numerical phantoms. Monoenergetic analytical simulations were compared with monoenergetic and polyenergetic Monte Carlo simulations. Analytical and Monte Carlo scatter estimates were compared both qualitatively, from visual inspection of images and profiles, and quantitatively, using a scaled root-mean-square difference metric. Reconstruction of simulated cone-beam projection data of an anthropomorphic breast phantom illustrated the potential of this method as a component of a scatter correction algorithm.
  
  
  RESULTS
  The monoenergetic analytical and Monte Carlo scatter estimates showed very good agreement. The monoenergetic analytical estimates showed good agreement for Compton single scatter and reasonable agreement for Rayleigh single scatter when compared with polyenergetic Monte Carlo estimates. For a voxelized phantom with dimensions 128 × 128 × 128 voxels and a detector with 256 × 256 pixels, the analytical estimator required 669 seconds for a single projection, using a single NVIDIA 9800 GX2 video card. Accounting for first order scatter in cone-beam image reconstruction improves the contrast to noise ratio of the reconstructed images.
  
  
  CONCLUSIONS
  The analytical scatter estimator, implemented using graphics processing units, provides rapid and accurate estimates of single scatter and with further acceleration and a method to account for multiple scatter may be useful for practical scatter correction schemes.
authors.affiliation: Division of Medical Physics, CancerCare Manitoba, McDermot Avenue, Winnipeg, Manitoba, Canada Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada Department of Radiology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Harry
authors.initials: H
authors.lastname: Ingleby
authors.affiliation: Division of Medical Physics, CancerCare Manitoba, McDermot Avenue, Winnipeg, Manitoba, Canada.
authors.forename: Jonas
authors.initials: J
authors.lastname: Lippuner
authors.affiliation: Division of Medical Physics, CancerCare Manitoba, McDermot Avenue, Winnipeg, Manitoba, Canada Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada Department of Radiology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Rickey
authors.affiliation: Division of Medical Physics, CancerCare Manitoba, McDermot Avenue, Winnipeg, Manitoba, Canada.
authors.forename: Yue
authors.initials: Y
authors.lastname: Li
authors.affiliation: Division of Medical Physics, CancerCare Manitoba, McDermot Avenue, Winnipeg, Manitoba, Canada Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada Department of Radiology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Idris
authors.initials: I
authors.lastname: Elbakri
mesh_terms: D054893:Cone-Beam Computed Tomography / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008327:Mammography; D008954:Models, Biological; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012542:Scattering, Radiation
keywords: Scatter estimation; compton scatter; graphics processing units; rayleigh scatter