A Low-Cost Approach to High-Resolution, Single-Photon Imaging Using Columnar Scintillators and Image Intensifiers

Results are presented for a low-cost, ultra-high resolution gamma camera for small-animal SPECT and molecular imaging. The detector, known as Bazooka SPECT, employs a second-generation image intensifier which is directly coupled to a columnar CsI(Tl) scintillator. Operating in photon-counting mode, individual gamma-ray interactions are seen as clusters of signal, and significant improvement in spatial resolution is obtained by estimating the interaction position via Anger (centroid) estimation for individual clusters. Amplification of scintillator light prior to the optical path is advantageous compared to similar, low-light CCD gamma-cameras which solely apply gain in the CCD. With amplification from the image intensifier, the system is no longer limited by light loss from the optical path. This allows for a customizable optical system via lenses in a macro photography configuration and for the use of a low-cost, highspeed CCD. Experimental results show that Bazooka SPECT has an intrinsic resolution of approximately 150mum when the entire 25mm intensifier output screen is imaged onto the CCD. Better than 100mum resolution is attainable with less demagnification from the optical system. Initial indications are that this detector will serve as an attractive, inexpensive modular camera for high-resolution, multiple-pinhole, small-animal SPECT and molecular imaging.