Performance results of a new DOI detector block for a High Resolution PET-LSO Research Tomograph HRRT

To improve the spatial resolution and uniformity in modern high resolution brain PET systems over the entire field of view (FOV), it is necessary to a rchive the depth of interaction (DOI) information and correct for spatial r esolution degradation. In this work we present the performance results of a high resolution LSO/GSO phoswich block detector with DOI capability. This detector design will be used in the new CTI High Resolution Research Tomogr aph, ECAT HRRT. The two crystal layers (19x19x7.5 mm(3)) and a light guide are stacked on e ach other and mounted on a (2x2) PMT set, so that the corners of the phoswi ch are positioned over the PMT centers. The crystal phoswich is cut into an 8x8 matrix of discrete crystals. The separation of the LSO and the GSO lay er by pulse shape discrimination allows discrete DOI information to be obta ined. The high light output and the light guide design results in an accura te identification of the 128 single crystals per block. Flood source measur ements document a very good homogeneity of events, energy centroid stabilit y and energy resolution (14-20% FWHM) per single crystal. An intrinsic reso lution of similar to 1.3 mm and the DOI feasibility is extracted by coincid ence measurements with a single GSO crystal.