Reconstruction of two- and three-dimensional images from synthetic-collimator data

A novel SPECT collimation method, termed the synthetic collimator, is propo sed. The synthetic collimator employs a multiple-pinhole aperture and a hig h-resolution detector. The problem of multiplexing, normally associated wit h multiple pinholes, is reduced by obtaining projections at a number of pin hole-detector distances. Projections with little multiplexing are collected at small pinhole-detector distances and high-resolution projections are co llected at greater pinhole-detector distances. These projections are then r econstructed using the ML-EM algorithm, It is demonstrated through computer simulations that the synthetic collimator has superior resolution properti es to a high-resolution parallel-beam (HRPB) collimator and a specially bui lt ultra-high-resolution parallel-beam (UHRPB) collimator designed for our 0.38-mm pixel CdZnTe detectors. it is also shown that reconstructing images in three dimensions is superior to reconstructing them in two dimensions. The advantages of a high-resolution synthetic collimator over the parallel- hole collimators are apparently reduced in the presence of statistical nois e. However, a high-sensitivity synthetic collimator was designed which agai n shows superior properties to the parallel-hole collimators. Finally, it i s demonstrated that, for the cases studied, high-resolution detectors are n ecessary for the proper functionality of the synthetic collimator.