Jericho O'Connell, Magdalena Bazalova-Carter
FastCAT, a fast cone-beam computed tomography (CBCT) simulator is demonstrated. The fastCAT application uses pre-calculated Monte Carlo (MC) CBCT scatter and detector response functions to reduce simulation time for kV and MV CBCT. Pre-calculated x-ray beam energy spectra, detector optical spread functions and energy deposition, and phantom scatter kernels are combined with beam filtration and GPU raytracing to produce CBCT volumes. Source spectra are either simulated in EGSnrc using 2.5 and 6 MeV electron beams incident on a variety of target materials or analytical spectra from a tungsten x-ray tube. Detectors were modelled in Geant4 extended by Topas including optical transport in the scintillators. Two MV detectors were modelled, a standard Varian AS1200 GOS detector and a novel CWO high quantum efficiency detector. Energy dependent scatter kernels were created in Topas for a two 16-cm diameter water phantoms: a Catphan 515 contrast phantom and a spatial resolution phantom. The Catphan phantom contained inserts of 1-5 mm in diameter of six different tissue types. These pre-calculated MC datasets allow the user to create CT volumes with custom phantom inserts, imaging beam, focal spots and detector combinations. FastCAT simulations retain high fidelity to measurements and MC simulations: MTF curves were within 1.1% and 4.8% of measured values for the CWO and GOS detectors, respectively. Contrast in a fastCAT Catphan 515 simulation was seen to be within 1% of an equivalent MC simulation for all of the tissues. A fastCAT simulation of the Catphan 515 module at a resolution of 1024x1024x10 took 61 seconds on a GPU while the equivalent Topas MC was estimated to take approximately 5.6 CPU years. We present an open source fast CBCT simulation with high fidelity to MC simulations. The fastCAT application can be found at this https URL
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