Improving the performance of small planar detectors for dedicated PET instruments

Several dedicated PET instruments for small animal and breast imaging have recently been developed. Many of these use position-sensitive photomultiplier tubes (PS-PMTs) and pixelated crystals with depth encoding scheme to detect and localize gamma rays. Large area PS-PMTs show more distortion and have difficulty identifying crystal elements near their periphery. We have recently enhanced the bismuth germinate (BGO) detector modules used in the our positron emission mammography (PEM) and animal PET (ANIPET) systems by modifying the crossed anode readout resistor chain, applying a faster timing amplifier circuit, which takes the last dynode signal as event timing and adding a new image weighting function to improve the crystal identification. The PMTs field-of-view (FOV) have increased from 46 /spl times/ 58 mm to 56 /spl times/ 64 min and the timing resolution of system has improved from 12.0 to 8.7 ns.