I. Introduction
Gamma-ray imaging is a powerful tool that can be used for the detection, localization, and characterization of radioactive sources in an environment. Such capabilities are critical to numerous applications, including emergency response and contamination remediation [1], nuclear security and safeguards [2], and nuclear medicine [3]. Of particular interest to this work is the role of gamma-ray imaging in resolving morphological features associated with the emission of gamma rays over a broad range of energies from 100 keV to 1 MeV in the near field. Here, we consider the near field to be in the order of the extension of the imaging instrument where beam divergence and solid angle effects need to be factored into the image reconstruction.