During this reporting period the emphasis of the work was on completion of a fully working small field of view scintillation camera to support future stimulation studies in monkeys and other small animals. To this end, analog gain correction circuits necessary for the operation of one complete device were designed, fabricated and tested. Other correction circuits offering smaller improvements in performance (such as corrections in spatial linearity, etc.) were deferred to a later time. Static imaging tests of this prototype system indicated that it met most of the requirements necessary for successful small animal imaging. As a result, a number of imaging studies were conducted in the guinea pig in order to define the behavior of the system under realistic conditions. Satisfactory static images of bone metabolism and lung perfusion were obtained with Tc- labelled MDP and MAA, respectively. Gated blood pool imaging of the heart, performed with Tc-HSA, showed the left and right ventricles as separate and LV ejection fraction to be about 60%. Phase and amplitude images showed the expected normal patterns, as did the distribution of myocardial perfusion portrayed in an ECG-gated Sestamibi perfusion study. This camera, which uses parallel hole collimation for image formation and a single position-sensitive photomultiplier tube for event location, appears capable of yielding high quality scintigraphic images of small animal organs. Further refinements to this system are being made and plans for using this system in stimulation studies in monkeys and other small animals are being formulated.
