Detector blocks for high resolution positron emission tomography.

Different designs of high-resolution positron camera systems have been investigated. The design goal is an instrument that can measure the whole brain with a spatial resolu-tion of 5 mm FWHM in all directions. An overall spatial resolution of 5 mm requires crystal dimensions of 6 x 6 x L mm3, or less, L being the length of the crystal. Timing and energy requirements necessitate high-performance photomultipliers. The small size scintillator crystals can currently only be read in schemes based on Anger techniques or by utilizing surface-sensitive PMTs. In the future, photodiodes can replace photomultipliers. In the present work, two different approaches have been investigated: Anger tech-niques and position- sensitive PMTS. Preliminary results of the two detector designs are reported. A tentative positron camera design Two different schemes to identify small BGO crystals have been investigated. One is based on crystal identification via Anger logic, while in the other scheme the crysta