Benefits of 3D scatter correction for the HRRT - a large axial FOV PET scanner

The scatter estimation method (SC-2D) designed for whole body (WB) scanner is currently used for the HRRT scanner. SC-2D neglects the difference in shape between scattered coincidences in direct and oblique sinograms. However, the difference may be significant for HRRT sinograms with larger oblique angles. We have extended the SC-2D method into a new method (SC-3D), which computes the scatter in oblique sinograms. We have used simulated data of a cylindrical phantom and anthropomorphic phantom to compare the results of the two methods with simulated scatter (SC-SIM). The results showed a negative bias of 5 % in the center of the cylinder image using SC-2D; a bias which was corrected by SC-3D. A similar but smaller bias was found for the anthropomorphic phantom images.