Subsurface Laser Engraving Techniques for Scintillator Crystals: Methods, Applications, and Advantages

Abstract

Pixelated scintillators are commonly used for gamma radiation detection in PET scanners. Dimensions, surface treatment, and reflector thickness affect the resolution and sensitivity of the detector and increase the signal to noise ratio. Pixel arrays fabrication is laborious and expensive, while by including nonscintillating material the active area of the detector is reduced. This process can be simplified and improved by the application of subsurface laser engraving techniques, where a grid of laser-induced microcracks form semitransparent walls inside the scintillator. Conceptual development of such patterns including simulations and photometric measurements is presented as a proof that pixelation without the application of external reflectors is possible, liberating pixel size and shape and allowing detector-specific patterns to be created. To demonstrate this, a case study of a hexagonal grid of pixels of 1.4 mm $^{2}$ size on LYSO monolithic scintillators is proposed and results presented. Depth of interaction is also implemented on same size pixels, through different approaches. Advantages, concerning sensitivity, packing fraction, and cost effectiveness are discussed, supporting the viability of the process as an alternative to conventional pixelated array fabrication techniques which combines advantageous characteristics of both monolithic and pixelated scintillators.