Digital reconstruction of three-dimensional images from data coded by circular symmetry codes

The detector used is a Nuclear Chicago LFOV camera with a circular field of diameter 40 cm. A variable geometry system was built to fit onto the head of this camera in place of the normal collimator, enabling a mobile coding screen, lead-shielded to slop all photons other than those passing through the screen, to be displaced continuously between the crystal and the object. The maximum detector-coding screen distance is equal to the diameter of the detector. In a first series of experiments the coded images of test objects were recorded by both Fresnel coding and annular coding corresponding to different numbers of photons collected. The data, recorded in the form of an NxN matrix of numbers (N=64), are processed on an IBM.I68-370 computer with a computing programme based on the decoding method analysed. What will be the advantage of coding decoding gammography. That of forming a three-dimensional image without movement of either the object or the detector with a possible gain on the S/B ratio for a low field occupation coefficient. The methode thus offers interesting prospects for certain nuclear medicine examinations and for dynamic studies in particular