NEW HIGH-Z SEMICONDUCTOR SENSOR FOR POSITRON TOMOGRAPHY

POSITRON EMISSION TOMOGRAPHY (PET) IS A NONINVASIVE, MEDICAL IMAGING TECHNIQUE THAT PROVIDES AN IMAGE OF A POSITRON-EMITTING RADIOPHARMACEUTICAL AND ITS DISTRIBUTION IN THE BODY ON A METABOLIC LEVEL. IT IS BECOMING AN IMPORTANT FUNDAMENTAL TOOL FOR BOTH CLINICAL DIAGNOSIS AND MEDICAL RESEARCH. THE HEART OF THIS INSTRUMENT IS A LARGE, CIRCULAR ARRAY OF GAMMA-RAY DETECTORS. THE COMPLEXITY, COST, AND DIFFICULTY OF BUILDING AN INSTRUMENT WITH HUNDREDS OF THESE BULKY AND FRABILE PHOTOSENSORS IS A SIGNIFICANT PROBLEM. THE AVAILABILITY OF A SUITABLE SOLID-STATE SENSOR TO REPLACE THE PHOTOTUBES AND SCINTILLATOR CRYSTALS WOULD BE A MAJOR BREAKTHROUGH IN THE DESIGN OF HIGH-RESOLUTION PET CAMERAS. SUCH A SENSOR WOULD DETECT THE 511-KEV PHOTONS DIRECTLY TO PRODUCE AN ELECTRONIC PULSE WITHOUT AN INTERMEDIATE OPTICAL CONVERSION. IT WOULD BE A SMALL, STABLE DEVICE THAT WOULD MAKE CONSTRUCTION OF RUGGED, COMPACT MULTIDETECTOR ARRAYS FOR PET SYSTEMS A REALITY. AT RADIATION MONITORING DEVICES, INC., GAMMA-RAY DETECTORS MADE FROM A NEW SEMICONDUCTOR MATERIAL, THALLIUM BROMIDE (T1BR), HAVE BEEN INVESTIGATED. T1BR HAS THE SAME EFFECTIVEZ AS BGO, THE LEADING SCINTILLATOR MATERIAL USED FOR PET, AND HIGHER DENSITY. PRELIMINARY RESULTS INDICATE IT HAS THE POTENTIAL FOR LOW NOISE AND HIGH-ENERGY RESOLUTION.