Development of a prototype system of a small bore DOI-PET Scanner

Small animal positron emission tomography (PET) scanners and positron emission mammography (PEM) scanner require not only high spatial resolution but also high scanner sensitivity. One of methods to achieve high scanner sensitivity is to move gamma ray detectors closer to objects. However it increases the gamma rays entering to the detector obliquely. Therefore, spatial resolution of reconstructed images is degraded. The solution of the degradation is using depth-of-interaction (DOI) detectors which can measure interaction positions of depth directions in scintillation crystals. We are developing a small bore PET scanner to achieve high sensitivity as well as high spatial resolution by the use of four-layer DOI information of the detector. We constructed and tested the prototype scanner of the four-layer DOI detectors. The prototype system consists of the six DOI detectors arranged hexagonally. The distance between the opposed DOI detectors is 9.2 cm and a field-of-view (FOV) is 8.8 cm. The DOI detectors consist of a 32 (transaxial) x 32 (axial) x 4 (depth) array of LGSO crystals and a 256ch FP-PMT. The size of each crystal element is 1.46 mm x 1.46 mm x 4.5 mm. In the presentation, the experimental data, especially the evaluation of the spatial resolution and sensitivity of the scanner, are presented.2008 Nuclear Science Symposium, Medical Imaging Conferenc