Measurements and Ray-Tracing Simulations of Light Spread in LSO Crystals

We report on measurements of the absolute light output from LSO crystals for irradiation with 511 keV gamma rays as a function of interaction position, reflector arrangement, detector coupling geometry and optical coupling to an adjacent crystal. The light output for this series of geometrical configurations is simulated with the ZEMAX ray-tracing software. By fine-tuning the optical parameters of the bulk and at the interfaces of the crystal, a model is obtained which yields good agreement with experimental data for all configurations. The resulting parameter set is applied to calculate the light distribution in a 12 times 12 crystal block detector. A comparison of measured and calculated block position profiles shows good agreement, demonstrating the potential of the simulation model to predict block detector performance data and provide guidelines for future array designs.