Monte carlo simulation of four-layer DOI detector with relative offset in animal PET

We have built a four-layer detector to obtain the depth of interaction (DOI) information in which all four layers have a relative offset of a half crystal pitch with each other. The main characteristics of the detector, especially the energy and spatial resolutions, strongly depend on the crystal surface treatments. As a part of the work for the development of an animal PET, we have investigated the effect of crystal surface treatment on the detector performances by Monte Carlo simulation, in order to optimize the surface condition of crystals composing a four-layer detector. The proposed detector consists of four LYSO layers with a crystal dimension of 1.5 mm × 1.5 mm × 7.0 mm. A simulation tool, DETECT2000, was used and validated against the experimental results, flood images acquired by prototype module. Spatial resolution and sensitivity were simulated by varying the surface treatment in crystals. In this study, the optimal surface condition of the four-layer crystals was derived for small animal PET with a view towards achieving high sensitivity as well as high and uniform radial resolution.