Reconstruction of an Inaccessible, Large-Area Extended Source with a SCoTSS Compton Gamma Imager

Compton gamma imagers are instruments which use the physics of Compton scattering to locate gamma emitters. This makes Compton gamma imagers useful tools for determining the distribution of radionuclides within an area which has restricted access. Our group has developed a Compton gamma imager which we call the silicon photomultiplier-based Compton telescope for safety and security (SCoTSS). Using a SCoTSS instrument, we made measurements of an extended source of La-140 that lay within an inaccessible area and implemented a tomographic back-projection algorithm to reconstruct the distribution. We demonstrate our method on simulated data of a point source of La-140 and two extended sources of La-140 for initial validation, and then apply our method to experimental measurements. Our method demonstrates good ability to localize the distribution of La-140 in all cases. Future improvements to our method will include the implementation of iterative methods and quantitative methods to estimate the reconstructed activity.