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Subsurface laser engraving to pixelate scintillation crystals used in PET/PEM detectors

Scintillator crystals are widely used as ionizing radiation detectors in nuclear medicine imaging equipment. In many detectors, arrays of small scintillator elements (pixels), optically isolated from each other by a reflective material, are used to provide information on the interaction position of photons in the crystal. The attainable spatial resolution is related to the pixel size. The technique of subsurface laser engraving has been proposed as a low-cost alternative to scintillation crystals arrays to pixelate monolithic crystals. In this work, the first results of the implementation of the laser engraving technique to pixelate cerium doped lutetium yttrium oxyorthosilicate (LYSO:Ce) scintillation crystals in the new Laser Engraving Laboratory at the UNAM Institute of Physics are presented. We characterized the shape and size of the induced microfractures with a Nd:YAG pulsed laser in LYSO crystal, and with this information, we optimized the engraving parameters to produce semi-transparent barriers that optically isolate one pixel from another, thus producing a 6×6 pixelated crystal array with pixel pitch of 1.67 mm.