Performance results of a prototype depth-encoding PET detector

The results of a feasibility study for a high-resolution PET detector syste m are presented. The detector is based on the use of etched LSO scintillati on crystals viewed from just one end. We have demonstrated that this config uration yields Depth-of-Interaction (DOI) information whilst also preservin g good energy and coincidence-time resolution. A prototype detector was bui lt using a 4x4 crystal array coupled to 61-pixel hybrid photodiodes. The me asurements demonstrate a. DOI resolution of 5 similar to 7mm FWHM in a 30mm deep detector. The signal level was measured to be in the range 250 to 600 photoelectrons depending on the location of the 511 keV energy deposit in the crystal. A resolving-time of less than 5ns FWHM was estimated based on indirect measurements. The technique depends on the assumption that all of the events detected above a selected threshold value are, in fact, full-ene rgy deposits. The validity of this assumption and the impact of the photons scattered in the object have been studied using a Monte Carlo simulation o f the proposed small animal PET imager.