A "mouse-sized" gamma camera for biological imaging

A compact detector, sized particularly for imaging a mouse, is described. The active area of the detector is approximately 48 mmtimes96 mm. Two flat-panel Hamamatsu H8500 position sensitive photomultiplier tubes (PSPMT) are coupled to a pixellated NaI(Tl) scintillator which views the animal through a copper-beryllium (CuBe) parallel-hole collimator. Because the PSPMTs have insensitive areas at their edges, particular care has been given to bridging the gap where the two tubes join so as to maintain uniform response across the entire rectangular area of the detector. The system described has been developed to optimize both sensitivity and resolution for in vivo imaging of small animals injected with iodinated compounds. We demonstrate an in vivo application of this detector by imaging a mouse injected with 10 muCi of ¹²⁵I