Fig. 1.

Contrast recovery coefficients determined in percentages for the 10-mm hot sphere, with 2-mm voxel size for analog and digital PET and with 1-mm voxel size for digital PET and displayed according to relative noise (coefficient of variation in the background, in percentages) for each number of iterations. Black symbols and dashed arrows represent the numbers of iterations considered to reach sufficiently high levels of convergence. This convergence was reached at 5 iterations for the digital PET with either 1-mm or 2-mm voxels size and at 10 iterations for the analog PET