Performance of a compact 64-pixel CsI(Tl)/Si PIN photodiode imaging module with IC readout

Summary form only received as follows: The authors present performance measurements for a complete 64-pixel compact gamma camera imaging module consisting of optically isolated 3×3×5 mm³ CsI(Tl) crystals coupled to a custom array of low-noise Si PIN photodiodes read out by a custom IC. The custom 64-pixel photodiode arrays at 50 V bias demonstrate an average leakage current of <30 pA/3×3 mm2 pixel, a >98% yield of pixels with <100 pA leakage, and a quantum efficiency of 75% for 540 nm CsI(Tl) scintillation photons. The custom 64-channel readout IC uses low-noise preamplifiers, shaper amplifiers, and a winner-take-all (WTA) multiplexer. Prototype ICs demonstrate low noise of 180 e- rms at 8 ms peaking time with a photodiode load (3 pF, 50 pA). Prototype detector modules using prototype ICs and prototype 12-pixel photodiode arrays yield an average room temperature energy resolution of 10.7% for the 140 keV gammas from ^99mTc. Intrinsic spatial resolution is determined almost entirely by the 3×3 mm² pixel size, and system spatial resolution depends on the collimator employed for the chosen application (e.g., scintimammography)