Analytical study of the effect of collimation on the performance of PET cameras in 3-D imaging

An analytical model was developed to evaluate the 3-D imaging performance of cylindrical PET (positron emission tomography) systems with the multislice and the volumetric configurations. Point-source event rates for singles and for true and scattered coincidences were obtained by numerical integration of the equations for probability of incidence on the detectors. Data were subsequently combined to extract the sensitivity and background (scatters and accidentals) count rates for various source dimensions and activity densities. Event rates before detection were evaluated, and an ideal tomograph geometry was assumed in order to investigate the fundamental properties inherent to the two tomograph designs. For small sources placed in a scattering cylinder, results indicate higher scatter and accidental fractions in the volumetric system. If the source activity is adjusted to produce the same true event rate (same sensitivity) in each tomograph, a comparable image contrast can be expected in the volumetric system for small size source and for high activity concentrations