A scatter-compensated crystal interference factor in component-based normalization for high-resolution whole-body PET

On a positron emission tomography (PET) scanner consisting of block detectors, coincidence responses to scattered radiation may differ from those to true depending on the crystal pair position within a coincidence block pair. Furthermore, these differences are considered to vary according to the radial position of the coincidence block pair. These conditions create ringing artifacts in the reconstructed image due to the lack of scatter compensation in detector normalization. In component-based normalization, a scatter-compensated crystal interference factor is therefore required in addition to the scatter-compensated block profile and intrinsic crystal efficiencies. In this study, we propose a scatter-compensated component-based normalization scheme using an annulus phantom, which provides true and scattered radiations over a large transaxial field of view, and evaluates the quality of three different-sized phantom images with whole-body PET. The results showed that the proposed normalization method significantly reduces the ringing artifacts in reconstructed images with different scattered/true fractions. The proposed algorithm, which introduced the scatter-compensated crystal interference factor, worked well under different scattered/true ratio conditions and was considered to be a robust, practical normalization method in high-resolution whole-body PET.