EMCCD-based photon-counting mini gamma camera with a spatial resolution < 100 /spl mu/m

Compact gamma cameras with high intrinsic spatial resolution and photon counting capabilities are very desirable for several applications in astronomy, biology and medicine. Here we present a novel photon-counting gamma camera that is based on an Electron-multiplying CCD (EMCCD). Effectively, the EMCCD has sub-electron read out noise, even at 50 frames per second. This high frame rate allows for analyzing individual scintillation events with respect to energy and position. In our camera, the EMCCD is Peltier cooled and a fiber optic taper with a CsI(Tl) columnar crystal layer are mounted on it. By cooling the CCD to -30 degC, dark current noise is negligible. Intrinsic resolution was determined using a line shaped gamma beam, and was better than 100 microns FWHM for both Co-57 and I-125. We conclude that EMCCDs combined with columnar crystals allow for constructing extremely high-resolution photon counting gamma cameras, which are suitable for pinhole SPECT