MC SIMULATION FOR ESTIMATION OF SCATTER INTENSITIES IN A CONE-BEAM CT SYSTEM EMPLOYING A 450 kV X-RAY TUBE

A Monte Carlo simulation, based on GEANT4, has been developed to compute the contribution of first order, second order, and higher order scattered radiation in a Computed Tomography (CT) system equipped with an industrial 450 kV X-ray tube and an area detector. The validation of simulation against the experimental data showed a good agreement. The amount of scattering produced by several hollow aluminum cylinders was simulated. It is shown that the scatter-to-primary ratio (SPR) is approximately 5% for the aluminum cylinder of outer diameter of 75 mm, 16% for the diameter of 100 mm, 91% for the diameter of 150 mm, and for the diameter of 200 mm it can rise to 230% in the regions corresponding to the maximum path length. Therefore, the scatter from the object significantly affects quantitative accuracy. Furthermore, the background scatter has been experimentally investigated. The results show that the background scatter plays an important rule and has to be reduced using collimators.