Design and performance of an EMCCD based detector for combined SPECT/CT imaging

We have designed and developed a very high sensitivity detector for near-simultaneous SPECT/CT imaging of small animals. The detector is based on a back-thinned electron multiplying charge coupled device (EMCCD) bonded to a fiberoptic window, and optically coupled to a high resolution, high efficiency, very thick microcolumnar CsI(Tl) scintillator via a fiberoptic taper. In addition to the low noise and high spatial resolution inherent to CCDs, the EMCCD provides controllable internal gain, which minimizes read noise even when the device is operated at high frame rates. This allows the detection of incident gamma-ray/X-ray radiation with high spatial resolution and enhanced signal-to-noise ratio (SNR). The use of thick microcolumnar CsI(Tl) offers high detection efficiency for gamma-ray/X-ray radiation while maintaining a high spatial resolution. This combination of the EMCCD and the CsI(Tl) scintillator has resulted in a unique detector that can be employed for near simultaneous functional (SPECT) and anatomical (X-ray CT) imaging at a reduced cost. The design and evaluation of the detector are discussed in this paper