Self-normalisation of emission data in 3D-PET

We demonstrate that dead-time mismatch between the normalisation and emission acquisitions in three-dimensional positron emission tomography (3D PET) can introduce high-frequency 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 normalisation 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 normalisation 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-normalisation” scheme can remove normalisation artifacts in phantom studies, and that it is also effective in vivo