An attenuated projector for iterative reconstruction algorithm of a novel Tomographic Gamma Scanner

Tomographic Gamma Scanners are novels tools for nondestructive assay and characterization of nuclear waste drums. In these scanners, a three dimensional image of the activity distribution of every radioisotope stored in the drum is obtained performing a single-photon emission tomography. ARTGS is a novel architecture of tomographic gamma scanners that combines an HPGe detector with six NaI(TI) detectors in order to achieve high-sensitivity. In this work, a projector for a 2D MLEM reconstruction algorithm of AR-TGS is presented. This projector models the geometry of the system, the collimator´s response and the attenuation in the field of view performing a ray-tracing with several lines of response per detector. The projector was evaluated with Monte Carlo simulations and an experimental measurement. The algorithm proved to be an accurate model of the acquisition process and was used to reconstruct data sets with different strategies. The results showed that the image reconstruction with this method improved considerably spatial resolution and image quality compared with an attenuated Siddon projector.