Development of a high resolution Si-PM based compact gamma camera system

Objectives Silicon photomultiplier (Si-PM) is a promising photodetector for PET with its high gain, small size, and especially for use in magnetic resonance imaging (MRI) system because it is less sensitive to static magnetic field. However these properties are also promising for gamma camera system for single photon imaging. Using the Si-PM, it will be possible to develop a gamma camera system for small animals. For this purpose, we developed a ultra high resolution Si-PM based compact gamma camera system.

Methods YSO was selected as scintillators because of the high light output and no contamination of the natural radioactivity. The developed gamma camera consists of 0.6mmx0.6mmx6mm YSO scitillators combined with 0.1mm thick reflector to form 17x17 matrix and optically coupled to a Si-PM array (Hamamatsu MPPC S11064-050P) with 2mm thick light guide. The YSO block size was 12mmx12mm. The YSO gamma camera was encased in a 5mm thick gamma shield, and parallel hole collimator was mounted in front of the gamma camera (0.5mm hole, 0.7mm separation, 5mm thick).

Results The position histogram for Co-57 gamma photons (122keV) was almost resolved. The energy resolution for the YSO block detector was 24% FWHM for Co-57 gamma photons (122keV). The spatial resolution at 1.5mm from the collimator surface was 1.3mm FWHM using a 1mm diameter Co-57 point source. Phantom and small animal images are successfully obtained using the gamma camera.

Conclusions We confirmed that the developed Si-PM based YSO gamma camera is promising for molecular imaging researches.

Research Support This work was partly supported by the National Institute of Biomedical Innovation