Self-normalization of emission data in 31) PET

We demonstrate that dead-time mismatch between the normalization and emission acquisitions in three-dimensional positron emission tomography (3D PET) can introduce highfrequency circular image artifacts. We describe a simple correction scheme for this problem where appropriate correction factors are calculated from the emission data itself, thus avoiding the necessity of acquiring normalization data at a range of different count-rates. In this scheme “pseudo detector efficiencies” are calculated from the emission data by application of a conventional normalization algorithm. The mean systematic variation in these pseudo-efficiencies with position within the block-detector is then calculated, and appropriate correction factors applied to the original emission data. We show that this “self-normalization” scheme can remove normalization artifacts in both uniform and nonuniform phantom studies, and that it is also effective in vivo.