Performance assessment of a slat gamma camera collimator for 511 keV imaging

The physical performance of a prototype slat collimator is described for ga mma camera planar imaging at 511 keV. Measurements were made of sensitivity , spatial resolution and a septal penetration index at 511 keV. These measu rements were repeated with a commercial parallel hole collimator designed f or 511 keV imaging. The slat collimator sensitivity was 22.9 times that of the parallel hole collimator with 10 cm tissue equivalent scatter material, and 16.8 times the parallel hole collimator sensitivity in air. Spatial re solution was also better for the slat collimator than the parallel hole col limator (FWHM at 10 cm in air 17.9 mm and 21.2 mm respectively). Septal pen etration was compared by a single value for the counts at 120 mm from the p oint source profile peak, expressed as a percentage of the peak counts, sho wing less penetration for the slat collimator than the parallel hole collim ator (1.9% versus 3.6% respectively). In conclusion, these results show tha t the slat collimator may have advantages over the parallel hole collimator for 511 keV imaging, though the greater complexity of operation of the sla t collimator and potential sources of artefact in slat collimator imaging a re recognized.