Study of high-energy multihole collimators

Recently, a general theoretical description of multihole collimators has been proposed by one of the authors. In this work, the theory was used to study the response to extended uniform-sources, so that hole array effects can be easily studied. The dependence of such effects on the detector-collimator distance was assessed and the existence of optimal distances for which they are minimized was found. The authors' theoretical predictions were compared with experimental data obtained with a specific camera-collimator system. A large field of view camera equipped with an high-energy general purpose collimator for I-131 with hexagonal holes placed in an hexagonal lattice was used. A series of images of flood source placed on the collimator external face, each with a different detector-collimator external face, each with a different detector-collimator distance was acquired. The qualitative analysis of the images clearly showed the existence of optimal distances to reduce the hole array artifacts. The quantitative analysis of data showed that the theoretical predictions were in agreement with the experience. These results may be useful for the design of new collimators, for the optimal arrangement of camera-collimator system and they may also foster the study of some artifacts compensation methods.