Development of a high-resolution PET detector using LSO and wavelength-shifting fibers

By using wavelength-shifting fibers coupled to thin plates of LSO and to photomultipliers, the authors have demonstrated spatial resolution of 2 mm FWHM for photocapture events. Optimized systems are believed to be capable of better than 1 mm FWHM resolution, without requiring either very small crystals or large numbers of photosensors. With this sensor resolution, annihilation acollinearity dominates system resolution for large PET rings. By radially stacking alternating layers of thin crystals and wavelength-shifting fibers, a direct depth-of-interaction measurement is possible. Energy measurements and coincidence timing may be provided by trigger photomultipliers in a dual-photodetector geometry. Results from computer simulations and component response measurements on proof-of-concept prototypes are presented.