Scintillator identification and performance characteristics of LSO and GSO PSPMT detector modules combined through common X and Y resistive dividers

Combining signal channels from detector arrays can reduce complexity and minimize cost but, potentially, at the expense of other performance parameters. We evaluated a method that reduces the number of signals by combining the anode outputs of three position-sensitive photomultiplier tubes (PSPMTs) through a common Ii resistive charge divider and three individual Y resistive charge dividers. Field flood images at 511 keV of two LSO modules combined with a single GSO module were compared to images obtained when the modules were illuminated separately. At moderate count rates only a small reduction in position detection accuracy was observed in the combined tubes. Event mis-positioning was minimal for total count rates < 300,000 cps. At higher rates, pulse pileup degraded accuracy. Delayed charge integration, a method for identifying scintillators by differences in their light decay times, allowed the LSO and GSO arrays to be distinguished from one another and also reduced the effect of pulse pileup. Thus, combining PSPMTs anodes through common X and common Y resistive dividers may be useful in reducing signal number from PSPMT detector modules while maintaining good event localization and scintillator identification accuracy at reasonable event rates.