Development of a high resolution detector for positron emission mammography

Various PET detector configurations were investigated for the design of a compact, high spatial resolution PET detector block for the PET/X system. This system is being designed as a dedicated breast imager with high quantitative accuracy for monitoring response to new cancer therapies. The block´s spatial resolution, count rate capability, number of readout channels, energy and timing resolution were optimized. Monte Carlo simulations were performed to model the expected singles rates from the breast and surrounding organs on the PET detector blocks. The results were used to optimize the block size and determine the expected pileup probability. Silicon photomultiplier based photosensor arrays from Hamamatsu and SensL were evaluated with two different scintillator arrays consisting of 2×2 mm² crystals separated by ESR and sub-surface laser engraving. Row/column readout electronics were used to study light sharing within the scintillator crystals and to optimize light spread through light guides when coupling the scintillators to the photosensors. 4-corner readout electronics were chosen to readout the detector block, as this minimized the number of readout channels per block. A block consisting of an ESR-separated LYSO crystal array coupled to Hamamatsu´s through-silicon-via MPPC array demonstrated excellent crystal resolvability, 14% energy resolution and 1.2 ns coincidence resolving time. In addition, the depth-of-interaction of the incident photons was found by adding an extra layer of ESR-separated LYSO crystals staggered by 1 mm in each axis.