fastCAT: Fast cone beam CT (CBCT) simulation

The fastCAT application uses pre-calculated Monte Carlo (MC) CBCT phantom-specific scatter and detector response functions to reduce simulation time for megavoltage (MV) kilovoltage (kV) imaging. Pre-calculated x-ray beam energy spectra, optical spread deposition, phantom kernels are combined with GPU raytracing produce volumes. MV spectra simulated EGSnrc 2.5 6 MeV electron beams incident on a variety of target materials kV calculated analytically an tube tungsten anode. Detectors were modelled in Geant4 extended by Topas included transport the scintillators. Two detectors modelled, standard Varian AS1200 GOS novel CWO high detective quantum efficiency detector. A CsI was also modelled. Energy dependent created two 16-cm diameter phantoms: Catphan 515 contrast anthropomorphic head phantom. contained inserts 1-5 mm six different tissue types. FastCAT simulations retain fidelity measurements MC simulations: MTF curves within 3.5% 1.2% measured values detectors, respectively. HU CNR seen be 95 % confidence intervals equivalent all tissues root mean squared errors less than 16 1.6 comparisons, module image size 1024x1024x10 voxels took 61 seconds while estimated take more 0.3 CPU years. can found at https://github.com/jerichooconnell/fastCATs.git.