Preliminary Imaging Performance of an Ultra-high Resolution Pinhole SPECT System Using an Intensified EMCCD Camera

This paper presents preliminary results achieved using an ultra-high resolution pinhole SPECT system for small animal imaging using I-125 radiotracers. This system is based on a very-high resolution gamma camera that consists of an intensified EMCCD (I-EMCCD) camera coupled to columnar CsI(Tl) scintillators. The I-EMCCD camera provides an active area of ~80mm diameter, an intrinsic resolution of ~60mum and a near perfect photon counting efficiency for detecting 27-35keV photons emitted by I-125. A single pinhole aperture with a 100mum diameter pinhole was used in these imaging studies based on both phantoms and mice injected with 1-125 NaCl solution. A reconstructed spatial resolution of <100 mum has been experimentally achieved. Given the ultra-high spatial resolution and the very low readout noise, the I-EMCCD camera has the potential of offering a further improved spatial resolution for small animal imaging applications with tracers labelled with multiple radioisotopes such as I-125, I-123 and Tc-99m etc. The I-EMCCD based gamma camera can be used for a proposed single photon emission microscope (SPEM) system that provides a sub-hundred micron resolution and a reasonable detection efficiency for small animal imaging.