Scintillator crystal readout with wavelength-shifting optical fibers

Wavelength-shifting fiber readout of scintillator crystals permits efficient discrete event localization over large scintillator areas, by flexibly interfacing position-sensitive photosensors or photosensor arrays to scintillator crystal surfaces. We describe techniques for localizing gamma-ray interactions within large crystals, and for determining the crystal of interaction within multicrystal arrays. Measurements carried out with NaI(Tl) coupled through fibers to photomultipliers confirm the technique´s expected light yield, and measurements with BGO coupled through fibers to avalanche photodiodes demonstrate the usefulness of this method for crystal-of-interaction determination. We use a block detector geometry, combining fiber localization with direct energy measurement by large photomultipliers. Potential applications for gamma cameras and for high resolution PET systems are discussed