Hybrid gamma ray imaging—Model and results

We report on a hybrid gamma-ray radiation imaging system for industrial applications that combine the advantages of a multi-aperture mechanical collimator with electronic collimation. The combination offers both efficiency and good angular resolution, and is unique since a single gamma ray can contribute information to both modalities simultaneously. The mechanically collimated camera is most effective for imaging lower energy photons while electronic collimation uncouples spatial resolution from efficiency for higher energies. Our proposed Hybrid Gamma Ray Imager combines a high-resolution URA coded aperture with a Compton scatter camera to provide a broader range of energy response suitable for a wider range of industrial applications (50 keV–2 MeV). The primary detector is a large-area LaCl3:Ce scintillator coupled directly to a Hammamatsu PSPMT, chosen to provide portability, efficiency and energy resolution. A pixellated CsI(Na)/PSPMT combination serves as the secondary absorption detector. Point and ring-shaped radiation sources (140, 364, 662 and 1275 keV) are simulated. The results show coverage over a broad energy range of radiation and better images than either a mechanical or an electronic imager at intermediate energies. The sensitivity loss of the electronic imager due to the introduction of the mechanical collimator is recognized.