Several groups are actively investigating the performance of monolithic (continuous) scintillation detectors using a variety of crystal thicknesses, photo-sensor configurations, and surface treatments. This work explores the performance of thick LYSO crystals that would be applicable to a whole-body PET system. The crystals were etched with laser induced optical barriers (LIOBs) to alter the behavior of the light spread within the crystal in order to improve the performance of the detector. We studied the behavior of the LIOBs in response to optical light using small cubes of LYSO with a variety of laser etching parameters to characterize the impact of the optical barriers. We demonstrated that the opacity of the etchings can be altered by varying the parameters of the laser etching, which influences the depth-dependent light response and spatial resolution in the thick crystal. We successfully etched several crystals, as large as 50×50×25-mm3 thick, with a fine grid of LIOBs, and achieved an average spatial resolution close to 3 mm (FWHM) with 511-keV gammas.
Keywords: Laser induced optical barriers; monolithic scintillators.