Hybrid Simulation of Scattering Distribution in Cone Beam CT

This paper presents a hybrid simulator for the fast calculation of x-ray projections. Uncollided radiations are determined with a ray-driven method whereas the scattering signal is partitioned into single and multiple scattering, respectively estimated with an accelerated deterministic method and a coarse Monte Carlo simulation. The simulator takes into account the full acquisition chain, from the emission of a polyenergetic beam of photons, their interactions with the scanned object until their energy deposit in the detector. Object phantoms can be spatially described in form of voxels, mathematical volume primitives or CAD models. The hybrid method has been validated with the Monte Carlo code Geant4 on aluminium phantoms with varying size and object-to-detector distance. Good agreement has been found between the two methods. The acceleration achieved by the hybrid method on a single projection lies between two to four orders of magnitude. The proposed simulator has been developed for industrial cone-beam CT scanners and the correction of scatter artefacts.