Design of a small animal PET system high detection efficiency

In most positron emission tomography (PEC) systems, the geometry of the detector module is based on a block structure where the crystal elements are coupled to a reduced number of photomultiplier tubes (PMT). In this configuration, the spatial resolution and the detection efficiency depend on the crystal dimensions and therefore those two figures of merit are correlated. The use of two or three crystal layers to estimate the depth of interaction reduces the correlation but does not remove it. In this paper, we present a method already introduced by Ter-Pogossian et al in the seventies allowing the spatial resolution and the detection efficiency to be independent The crystals are oriented in the axial direction readout on both sides by individual PMT channels. The spatial resolution in the radial direction is given by the section of the crystal and the spatial resolution in the axial direction is proportional to the contrast of the light collected at both sides of the crystal. The detection efficiency depends on the number of radial crystal layers and the geometry of the system. The proposed small animal PET system consists of a stack of inorganic scintillation crystals arranged in layers around the animal to form a complete cylinder. This geometrical configuration leads to a detection efficiency close to the system solid angle with a volumetric spatial resolution of 1 mm.