Effect of intercrystal Compton scatter on efficiency and image noise in small animal PET module

The effect of intercrystal Compton scatter in a small animal PET module was investigated using electron-gamma shower code (EGS4) simulations. The size of detector module is fixed at a 16 mm/spl times/16 mm crystal array. Monte Carlo simulations were performed to estimate the effect of intercrystal scatter considering scintillation materials (BGO, LSO, and NaI), detector energy threshold, crystal size, and interaction position estimation methods on the fraction of correct coincidence efficiency (FCCE). Results show the crystal size (2 mm/spl times/2 mm/spl times/10 mm) currently used in MicroPET has the highest FCCE. In order to evaluate spatial resolution and image noise due to intercrystal scatter, the coincidence line response function (CLRF) of detector modules and 2D images using the MicroPET R4 geometry were reconstructed. The results demonstrate a very small effect on FWHM but considerable noise and contrast loss in images due to the tails of the CLRF resulting from intercrystal scatter.