First results with high-resolution PET detector modules using wavelength-shifting fibers

We have constructed and tested prototype PET detector modules incorporating wavelength-shifting fiber ribbons alternating with thin CsI(Na) scintillator plates in multilayer stacks. Modules with cross-sectional area of 11cm x 11cm and with 9mm of total crystal thickness have been tested. A reconstructed spatial resolution of 3 mm FWHM has been obtained for a line source, with an energy resolution of < 20% and a time resolution of 25ns FWHM. Energy measurements and coincidence timing are provided by 4 photomultipliers in an Anger array on one 11cm x 11cm module face. Multiplexed fiber readout has been implemented with multianode photomultipliers coupled to several fiber ribbons. The methods and resolution achieved are readily extended to larger systems in a straightforward and cost-effective manner. Results of tests with several phantoms are presented.