TOMOGRAPHY CAMERAS-

POSITRON EMISSION TOMOGRAPHY (PET) IS A NONINVASIVE MEDICAL IMAGING TECHNIQUE THAT PROVIDES A THREE-DIMEN- SIONAL IMAGE OF RADIOPHARMACEUTICALS DISPERSED IN THE BODY. IT IS BECOMING AN IMPORTANT FUNDAMENTAL TOOL FOR BOTH CLINICAL DIAGNOSIS AND MEDICAL RESEARCH. THE HEART OF THIS INSTRUMENT IS A LARGE ARRAY OF NUCLEAR DETECTORS MOSTLY CONSISTING OF SCINTILLATOR CRYSTALS COUPLED TO PHOTOMULTIPLIER TUBES. THE COMPLEXITY, COST, AND DIFFICULTY OF BUILDING AN INSTRUMENT WITH HUNDREDS OF THESE BULKY AND FAGILE PHOTOSENSORS IS A SIGNIFICANT PROBLEM. THE AVAILABILITY OF A SUITABLE SEMICONDUCTOR SENSOR TO REPLACE THE PHOTOTUBES AND SCINTILLATOR CRYSTALS WOULD BE A MAJOR BREAKTHROUGH IN THE DESIGN OF POSITRON TOMOGRAPHY CAMERAS. THIS WOULD GREATLY REDUCE THE COST AND INCREASE THE PRACTICALITY OF PET CAMERAS. IT HAS LONG BEEN RECOGNIZED THAT DETECTORS MADE FROM THE SEMICONDUCTOR CADMIUM TELLURIDE (CDTE) ARE THEORETICALLY THE BEST CANDIDATES FOR USE AS A SEMICONDUCTOR SENSOR FOR PET CAMERAS. PREVIOUSLY, THIS TYPE OF DETECTOR WAS LIMITED BY BOTH SMALL ACTIVE VOLUMES AND THE INABILITY TO PROVIDE THE FAST RESPONSE NEEDED FOR THIS APPLICATION. A NEW CDTE DIODE STRUCTURE HAS RECENTLY BEEN STUDIED. AS A RESULT, SEVERAL OF THE PREVIOUS LIMITATIONS OF CDTE APPEAR TO HAVE BEEN OVER- COME. IT SHOULD NOW BE POSSIBLE TO MAKE FAST EFFICIENT CDTE SENSORS WITH THE CORRECT SIZE, SHAPE, AND SPEED OF RESPONSE FOR THIS IMPORTANT MEDICAL INSTRUMENT. THUS, THE PLANNED PROGRAM IS DIRECTED AT INVESTIGATING THE POSSIBILITY OF USING THIS NEW CDTE DETECTOR DESIGN FOR PET APPLICATIONS. STUDIES WILL BE DONE WITH RESPECT TO SENSITIVITY AND TIME RESPONSE TO POSITRONS AS WELL AS WITH OTHER DETECTOR PARAMETERS RELEVANT TO PET IMAGING. BY THE END OF PHASE I, THE FEASIBILITY OF THIS DETECTOR DESIGN FOR PET SCANNING SHOULD BE DEMON- STRATED.