Portable Active Collimation Imager Using URA Patterned Scintillator

A portable active collimator using systematically patterned scintillators was constructed and its performance evaluated. In the conventional passive radiation collimation method, single or multiple holes are used to limit radiation reaching a detector while radiation scattered in the collimator is not used. However in active collimation where one replaces the passive collimator with a radiation detector, both the radiation that passes through the holes and radiation scattered in the collimator can be used. The active collimator was composed of uniformly redundant array (URA)-patterned Bi₄Ge₃O₁₂ (BGO) scintillators with a CsI(Na) detector planar array positioned behind the collimator. Images using radiation passing through the holes of the URA collimator were reconstructed using the correlation method of conventional coded apertures, while the radiation scattered in the active collimator and detected in the planar detector, was imaged using a Compton imaging technique. Since the active collimation method uses both Compton scattered events and photoelectric absorption events, its detection efficiency and energy range are inherently higher than those of conventional collimation methods. The reconstructed images of the portable active collimation methods for various energy sources were obtained and compared with those of conventional methods.