Reconstruction Algorithm with Resolution Deconvolution in a Small-Animal PET Imager

Abstract

A small-animal PET imaging device has been developed at the University of Texas Southwestern Medical Center at Dallas using scintillating 1-mm round BCF10 fibers and small admixture of CsF microcrystals between the fibers [Antich, 1990, Atac, 1991, Fernando, 1996 ]. The fiber core is polystyrene (C 8 H 8 )n doped with butyl-PBD and dPOPOP. The fibers are clad in a non-scintillating lucite cladding. The scintillation mechanism can be either from the excitation of π electrons in the butyl-PBD benzene ring in the fiber or from excitation within the microcrystals. In both cases, the emitted light is compatible with the optimal spectral response of standard photomultiplier cathodes. For a 511 keV photon in plastic,the photo-absorption is small, and Compton scatter interactions are dominant. The scattered electrons give up their energy well within a fiber diameter, but wave-shifting produces light in proximal fibers. The current imager uses the 2-fold coincident detection of a single event in 2 orthogonal fibers of 1-mm diameter to detect the location and the energy transferred at a point within the detector. Two sets of fibers each 60 cm in length and 1 mm in diameter were used to construct two alternating, mutually orthogonal sets of 14 planar arrays of 135 fibers each. In this detector, the planar fiber arrays are arranged along two alternating mutually orthogonal (X and Y)axes and are stacked along a third (Z). Scintillating light from the fibers is detected by two (X and Y directions) Hamamatsu R-2486 Position Sensitive Photomultiplier Tubes (PSPMT). A single-ended readout scheme is used, where the X,Z and Y,Z interaction positions in a detector are determined from coincident detection in the two PSPMT. The precision of the detection of the interaction point depends upon PSPMT performance and software filters.