Enhanced γ-Ray Imaging Utilizing Coded Apertures with Pixelated Detectors

γ-rays cannot be focused, unlike lenses, which can focus on visible light. Therefore, a unique technique for the visualization of γ rays was implemented some decades ago, creating unique shadows of a multihole aperture on the film of a γ-ray telescope. Since then, coded apertures have been used in several aspects of ionizing radiation imaging, including telescopes, medical γ cameras, and portable γ-cameras for site characterization and inspection. Cadmium telluride (CdTe) technology provides pixelated detectors with fast electronics, tiny pixels, and high energy resolution. Mounting coded apertures in front of CdTe detectors can result in a wide field-of-view γ camera with excellent spatial resolution and good efficiency for low-to-medium energy photons. The evolution from two-dimensional (2D) γ-ray vision to 3D γ vision is presented in this chapter via a system comprising two γ-cameras. The capacities and effects of planar coded aperture imaging combined via the parallax phenomenon to localize the radioactive spots in 3D space. In the last two sections, the evolution of a system of two γ cameras is presented. The system flirts with intraoperative nuclear medicine applications, nuclear security identification, and imaging in the decommissioning of nuclear facilities. Examples of simulation and real experiments analyze a penumbra phenomenon, which reduces intrinsic noise and gives rise to the signal-to-noise ratio in the way a kernel filter does. Such demonstration of applied research may be helpful in the development of coded aperture applications by engineers and physicists.