Coupling an analytical description of anti-scatter grids with simulation software of radiographic systems using Monte Carlo code

摘要

The use of focused anti-scatter grids on digital radiographic systems with two-dimensional detectors producesacquisitions with a decreased scatter to primary ratio and thus improved contrast and resolution. Simulation software isof great interest in optimizing grid configuration according to a specific application. Classical simulators are based oncomplete detailed geometric descriptions of the grid. They are accurate but very time consuming since they use MonteCarlo code to simulate scatter within the high-frequency geometric description of the grid. We propose a new practicalmethod which couples an analytical simulation of the grid interaction with a radiographic system simulation program.First, a two dimensional matrix of probability depending on the grid is created offline, in which the first dimensionrepresents the angle of impact with respect to the normal to the grid lines and the other the energy of the photon. Thismatrix of probability is then used by the Monte Carlo simulation software in order to provide the final x-rays scatter fluximage. To evaluate the gain of CPU time, we define the increasing factor as the increase of CPU time of the simulationwith as or without the grid. Increasing factors were calculated with the new model and with classical methodsrepresenting the grid with a Computed-Aided Designed (CAD) model. With this new method, increasing factors areshortened by three to four orders of magnitude.