LEAD SULFATE SCINTILLATORS FOR USE IN POSITRON EMISSION TOMOGRAPHY

POSITRON EMISSION TOMOGRAPHY (PET) IS EMERGING AS AN IMPORTANT FUNDAMENTAL TOOL FOR BOTH CLINICAL DIAGNOSIS AND MEDICAL RESEARCH. PET IS A NONINVASIVE MEDICAL IMAGING TECHNIQUE THAT PROVIDES AN IMAGE OF THE DISTRIBUTION OF A POSITRON-EMITTING RADIOISOTOPE IN THE BODY. THE PERFORMANCE OF THIS INSTRUMENT IS LIMITED BY THE NUCLEAR DETECTORS USED. RESEARCHERS FROM LAWRENCE BERKELEY LABORATORY (LBL) HAVE DEVELOPED A PROMISING DUAL DETECTOR CONCEPT FOR GENERATING HIGH RESOLUTION POSITRON EMISSION TOMOGRAPHS. IN THIS CONCEPT, A PHOTOMULTIPLIER TUBE COUPLED TO SEVERAL SMALL SCINTILLATORS IS THE PRIMARY DETECTOR FOR DETERMINING THE TIME AND THE ENERGY OF INTERACTION, WHILE SMALL POSITION-SENSITIVE PHOTODETECTORS ATTACHED TO THE OTHER FACE OF THE SCINTILLATORS IDENTIFY THE CRYSTAL THAT SCINTILLATED AS WELL AS THE DEPTH OF INTERACTION. THE INFORMATION FROM BOTH DETECTORS IS THEN USED TO CONSTRUCT A HIGH RESOLUTION TOMOGRAPH. THE PHASE I PROJECT AIMS TO DEVELOP A NEW, FAST, HIGH ATOMIC NUMBER SCINTILLATOR, LEAD SULFATE (PBSO4), FOR USE IN THE LBL PET CONCEPT. IN PHASE I, PBSO4 CRYSTALS ARE GROWN AND CHARACTERIZED IN TERMS OF THEIR PHYSICAL AND OPTICAL PROPERTIES. THESE SYNTHETIC CRYSTALS ARE BEING COMPARED WITH NATURALLY OCCURRING CRYSTALS. IF SUCCESSFUL, THE USE OF PBSO4 SCINTILLATORS IN THE DUAL DETECTOR APPROACH PROMISES TO BE THE BREAKTHROUGH NEEDED FOR THE CONSTRUCTION OF A NEW GENERATION OF HIGH RESOLUTION, HIGH RATE PET IMAGING SYSTEMS.