A NEW TWO-DIMENSIONAL POSITION ENCODER FOR POSITRON EMISSION TOMOGRAPHY (PET)-

A NEW TWO-DIMENSIONAL POSITION ENCODER IS PLANNED FOR PET WITH POSITION RESOLUTION BETTER THAN 3 MM. THE NEW DETECTOR INCLUDES 32 BISMUTH GERMANATE (BGO) SCINTIL- LATION CRYSTALS MOUNTED ON A LIGHT GUIDE. THE LIGHT GUIDE PROVIDES A SQUARE ROOT SEPARATION OF THE LIGHT DISTRIBUTED FROM EACH CRYSTAL. THE LIGHT FROM THE LIGHT GUIDE IS DETECTED BY TWO DUAL HAMAMATSU PHOTO- MULTIPLIER TUBES (R1548) THAT ARE ONE INCH SQUARE. THE SIGNAL FROM EACH PHOTOMULTIPLIER IS PROCESSED THROUGH THE ENCODING ELECTRONICS TO PRODUCE A DIGITAL SIGNAL INDICATING A SIGNAL POSITION (1 OUT OF 32) FOR EACH 511 KEV GAMMA RAY IMPINGING ON THE DETECTOR. THE DIMENSIONS OF EACH OF THE 32 CRYSTALS ARE NOMINALLY 3 X 12 X 30 MM. IT IS ANTICIPATED THAT THE DETECTOR, INCLUDING CRYSTALS, LIGHT GUIDE, PHOTOMULTIPLIER, AND ELECTRONICS FOR THE 32-CRYSTAL ARRAY WILL COST $2,500 COMPARED TO THE ACTUAL COST OF $15,000 FOR 32 INDIVIDUAL CRYSTALS, PHOTOMULTIPLIERS, AND SETS OF ELECTRONICS.