Monte Carlo simulations of a high-resolution X-ray CT system for industrial applications

An X-ray computed tomography (CT) model based on the GEANT4 Monte Carlo code was developed for simulation of a cone-beam CT system for industrial applications. The full simulation of the X-ray tube, object, and area detector was considered. The model was validated through comparison with experimental measurements of different test objects. There is good agreement between the simulated and measured projections. To validate the model we reduced the beam aperture of the X-ray tube, using a source–collimator, to decrease the scattered radiation from the CT system structure and from the walls of the X-ray shielding room. The degradation of the image contrast using larger beam apertures is also shown. Thereafter, the CT model was used to calculate the spatial distribution and the magnitude of the scattered radiation from different objects. It has been assessed that the scatter-to-primary ratio (SPR) is below 5% for small aluminum objects (approx. 5 cm path length), and in the case of large aluminum objects (approx. 20 cm path length) it can reach up to a factor of 3 in the region corresponding to the maximum path length. Therefore, the scatter from the object significantly affects quantitative accuracy. The model was also used to evaluate the degradation of the image contrast due to the detector box.