Simulated study of parallel-beam gamma ray tomography and image reconstruction

Transmission of gamma rays through a heterogeneous specific phantom was simulated using a Monte Carlo code for gamma diffusion simulation. Parallel beams transmission tomography arrangement using NaI(Tl) detectors and 60Co sources were used to establishing the geometric conditions. The measurement of the attenuation data of the incident radiation provided a measure of the line integral of the local mass density distribution along the path traversed by the beam. Several such beams at different spatial and angular orientations with respect to the test section or volume, followed by an image reconstruction procedure using filtered back-projection algorithm, provided a density distribution of phases to a high degree of spatial resolution. The phantom used was a cylindrical object containing water and some small elements of different materials inside was studied. System proprieties just as dimensions, positions and attenuation coefficients were required as input data for the simulation software. Factors related with the sample spacing, number of projections, back-projection reconstruction filtering and interpolation were tested in order to simulate the influence on the reconstructed image. (author)