Design features and performance of a CsI(Na) array based gamma camera for small animal gene research

We report on the development and performance of a radiation imaging system based on a 110 mm diameter matrix of 1 mm x 1 mm size CsI(Na) scintillating crystals. This detector system has been optimized for high resolution radi ation imaging of the distribution of iodine 125 (I-125) in a laboratory ani mal. The radioisotope I-125 is readily available as a label to molecular bi ology probes that can be used in gene research. The system utilizes the Ham amatsu 5 inch diameter 3292 position sensitive photomultiplier tube (PSPMT) coupled to the CsI(Na) matrix and a custom built high resolution copper-be ryllium collimator. A resulting spatial resolution of the order of 1.5 mm F WHM and a sensitivity of 68 cpm/mu Ci were obtained with the copper-berylli um collimator. The detector system is installed on a rotating gantry to obt ain multiple projections and is now being used in animal studies.