To achieve high spatial resolution required in nuclear imaging, scintillation light spread has to be controlled. This has
been traditionally achieved by introducing structures in the bulk of scintillation materials; typically by mechanical
pixelation of scintillators and fill the resultant inter-pixel gaps by reflecting materials. Mechanical pixelation however, is
accompanied by various cost and complexity issues especially for hard, brittle and hygroscopic materials. For example
LSO and LYSO, hard and brittle scintillators of interest to medical imaging community, are known to crack under thermal
and mechanical stress; the material yield drops quickly with large arrays with high aspect ratio pixels and therefore the
pixelation process cost increases.
We are utilizing a novel technique named Laser Induced Optical Barriers (LIOB) for pixelation of scintillators that
overcomes the issues associated with mechanical pixelation. In this technique, we can introduce optical barriers within the
bulk of scintillator crystals to form pixelated arrays with small pixel size and large thickness. We applied LIOB to LYSO
using a high-frequency solid-state laser. Arrays with different crystal thickness (5 to 20 mm thick), and pixel size (0.8×0.8
to 1.5×1.5 mm2) were fabricated and tested. The width of the optical barriers were controlled by fine-tuning key parameters
such as lens focal spot size and laser energy density.
Here we report on LIOB process, its optimization, and the optical crosstalk measurements using X-rays. There are
many applications that can potentially benefit from LIOB including but not limited to clinical/pre-clinical PET and SPECT
systems, and photon counting CT detectors.