Construction of a pre-clinical High Resolution Tomographic Scintillation camera system

We are constructing a High Resolution Tomographic Scintillation Camera System for small animal imaging. The system consists of a CsI(Tl) scintillator coupled to a military surplus image intensifier with a CCD camera focused on the output window. The system operates in photons counting mode and the spatial resolution is improved by centroid calculations for every photon interaction. The system can be mounted on an optical rail together with a pinhole collimator and a rotating table. A hot rod phantom was filled with ²⁰¹Tl or ^99mTc solute and imaged. The phantom rod diameters range from 1.1 to 1.6 mm. 64 projections were acquired (300 s/projection) with 1 mm pinhole insert. Data was reconstructed using an OSEM algorithm. Image data was corrected for decay, position non-linearities in image intensifier and the angular dependence of the pinhole. The reconstructed resolution is 1.3 mm (by visual inspection) for both ^99mTc and ²⁰¹Tl. Higher spatial resolution is achievable with smaller pinhole diameters. Future work includes optimizing spatial resolution and sensitivity of a single system using analytical calculations, experiments and simulations. With the conclusions drawn from those calculations we plan to construct a multi-camera system.