Development of an ultrahigh-resolution Si-PM-based dual-head GAGG coincidence imaging system

Objectives A silicon photomultiplier (Si-PM) is a promising photodetector for high resolution PET systems due to its small channels and high gain. Using Si-PM aray, it may be possible to develop a ultrahigh-resolution PET system. For testing the possibility, we developed a small field-of-view (FOV) ultrahigh-resolution Si-PM-based dual-head coincidence imaging system for small animals.

Methods A new scintillator, GAGG, was selected because of its high light output and its emission wavelength matched with the Si-PM arrays and contained no radioactivity. Each coincidence imaging block detector consists of 0.5 x 0.5 x 5 mm GAGG pixels combined with a 0.1-mm thick reflector to form a 20 x 17 matrix that was optically coupled to a Si-PM array (Hamamatsu MPPC S11064-050P) with a 1.5-mm thick light guide. The GAGG block size was 12.0 x 10.2 mm. Two GAGG block detectors were positioned face to face and set on a flexible arm based detector stand.

Results All 0.5-mm GAGG pixels in the block detectors were clearly resolved in the 2-dimensional position histogram. The energy resolution was 14.4% FWHM for the Cs-137 gamma photons. The spatial resolution was 0.7-mm FWHM measured using a 0.25-mm diameter Na-22 point source. Small animal images were successfully obtained.

Conclusions We conclude that our developed ultrahigh-resolution Si-PM-based dual-head coincidence imaging system is promising for small animals imaging researches.

Research Support This work was partly supported by the Ministry of Education, Science, Sports and Culture, Japan and the Japan Science and Technology Association, Japan