Influence of crystal geometry and wall reflectivity on scintillation photon yield and energy resolution

Small field-of-view PET and SPECT cameras for e.g. animal measurements gained an important role in the development of new camera techniques. In order to achieve both a good spatial and energy resolution a high number of scintillation photons have to reach the photocathode of a photomultiplier tube. This paper deals with the light output of different surface treatments and reflectors at CsJ(Na) crystal needles by simulations and measurements. The measurements using different geometries and surfaces of CsJ(Na) needles showed a high influence of the surface treatment and choice of the external reflector on the photoelectron output and energy resolution of crystal-matrix based camera system. The simulation program DETECT produces probable unreliable results with most of the possible surface models, but seem to work in a proper range when using the PAINT or the GROUND model