The effect of collimation on scatter fraction in multi-slice PET
The scatter fraction in a positron-emission tomograph (PET) depends on the collimator size and shape. Monte Carlo techniques were used to estimate the scatter fraction in multislice PET. Simulations of bismuth germanate detector arrays of 51 and 64 cm in diameter and a field of view 25 cm in diameter and 9.5 cm axially were done for a 20-cm-diameter phantom. Scatter fractions for one central, direct 1-cm-thick slice varied between 12% for a 15-slice geometry with 2-mm tungsten interslice septa to 43% for one slice with true 3-D collimation without septa. These values compare with an 8% scatter fraction with a 1-cm opening between lead collimators in a single-slice geometry. The scatter fraction in a transmission scan on a 20-cm source is higher than in an emission scan. >