Portable and active collimation imager using URA patterned scintillator

A portable and active collimator using systematically patterned scintillators was constructed and its performance was evaluated. The conventional (passive) radiation collimation method involved passing radiation through a single or multiple holes in the collimator, but it discarded scattered radiation. However, the new collimation method, in which the collimator itself is replaced by a radiation detector, uses not only radiation which passed through holes but also the scattered radiation in the collimator. The active collimator was composed of URA (Uniformly Redundant Array) patterned BGO scintillators and a CsI(Na) planar array positioned at the back of the collimator. The passing of radiation through the holes of the URA collimator was reconstructed using the correlation method of conventional coded apertures, while the scattered radiation in the active collimator, if detected in the planar detector, was recovered using a Compton imaging technique. Since the active collimation method uses Compton scattering events as well as photoelectric effect events, its detection efficiency and energy range are inherently higher than those of conventional collimation methods. The reconstructed images of the portable and active collimation methods for various energy sources were obtained and compared with those of conventional methods.