Fig. 1

Evolution, according to the number of equivalent iterations of image reconstructions, of the grey-to-white matter contrast from occipital cortex (black symbols, corresponding scale on the left side) and of the relative noise index from semi-oval centers (white symbols, corresponding scale on the right side), on the SPECT images of the brain phantom recorded with the conventional Anger gamma camera (squares), as well as with full-time (triangles) and half-time (circles) recordings from the CZT camera. The number of equivalent iterations considered to reach a high enough convergence for contrast and with an acceptable noise level is indicated by vertical dashed lines. The level of relative noise reached by the CZT-camera at these optimal convergence levels (0.17 for both half-time and full-time recordings) is additionally indicated by a horizontal dashed line