Using Monte Carlo to explore 3D reconstruction to geological application: preliminary characterization of technique limitations

摘要

The main objective of this project was to define a methodology for sediments characterization, imaging the material deposited in the tanks or in locu. It was evaluated the 3D reconstruction of the simulated planar images and the definition of limitations of the technique by simulating the sediment images. The strategy defined was to use as base material acetylene and as object of contrast (OC) acetylene with 10% of barium. Deterministic calculations were used to estimate some limitations of the technique by estimating the subject contrast (SC) and the transmission (T). The XRMC version 6.5.0-2 was used to generate the planar images, simulating 360 degrees in steps of 1 degree. The Feldkamp-David-Kress (FDK) reconstruction method was used to generate 3D images. The reconstructed images were evaluated (by using automated macros in Fiji) considering the dimensions of the OC and the sign, sign-to-noise ratio among other characteristic of the image sing. The deterministic calculation guided the selection of realistic spectra giving an idea about the limitation of the technique. The simulated images confirmed the limitation, for monochromatic incident photons beam of 30 keV, to image thicknesses up to 30 cm. Ir-192 was used to image larger thicknesses with consistent results. The XRMC proved to be an interesting and useful tool to generate geological images and guide on new strategies to image sediments. The results show that FDK reconstruction method can be used, but this method needs to be improved for reconstruct images with low contrast and high noise. Partial angular samples cannot be reconstructed with the FDK method.