Septa design study for volumetric imaging in positron emission tomography

Positron emission tomography (PET) has become an essential imaging tool to localize tumors in diagnostic radiology and to monitor the size of a lesion before and during the treatment in oncology. Currently, commercial PET cameras operate only in two extreme modes: (i) no-septa: 3D acquisition mode, also called volumetric imaging and, (ii) all-septa-in: 2D acquisition mode, also called multi-slice imaging. In this study, intermediate septa designs have been sought to minimize the scatter and accidental coincidences with acceptable sensitivity loss. To achieve this goal, Monte Carlo simulations were performed to evaluate possible septa designs. Information about septal penetration, absorption and scattering components from simulations guided us to modify the thickness and total number of septa in the new configurations. With the proposed designs, simulation results have estimated a 27-34% reduction in scatter component and 72-84% in accidentals at 0.2μCi/cc activity density in the brain mode. True sensitivities were reduced to 35-53% compared to no-septa case. Noise equivalent count rates (NEC) were measured and compared for three septa configurations.