Initial results from a PET/planar small animal imaging system

A pair of stationary, opposed scintillation detectors in time coincidence is being used to create planar projection or tomographic images of small animals injected with positron-emitting radiotracers. The detectors are comprised of arrays of individual crystals of bismuth germanate coupled to position-sensitive photomultiplier tubes. In projection mode, the animal is placed within the 55 mm/spl times/45 mm useful field-of-view of the detectors and images are formed from coincidence lines that fall close to the normals of both detectors. In tomographic mode, the animal is placed on a rotation stage between the detectors and rotated around a vertical axis to acquire all possible lines-of-response. Tomographic images are then reconstructed from lines-of-response falling within a user-specified angle of each detector normal. In mice, the system is capable of high-speed, whole-body dynamic projection imaging, and whole body tomographic imaging of semi-static tracer distributions. An ECG gating capability is also available for evaluating cardiac function. This system is currently being used to study tracer transport in normal and genetically altered mice.