Detectors with dual-ended readout by silicon photomultipliers for high resolution positron emission mammography applications

We used silicon photomultipliers coupled to LYSO scintillator crystals in dual-ended readout configuration to evaluate detector performance for depth of interaction (DOI) positron emission tomography (PET) applications. By experiments and Monte Carlo simulation, we investigated the effect of scintillator crystal geometry and surface finishing on DOI, energy and timing resolution. Measurements indicate almost linear dependency of signal asymmetry on DOI, with sensitivity of 7.1% mm-1 and DOI resolution of 2.1 + 0.6 mm for saw-cut, and 1.3% mm-1 and 9.0 ± 1.5 mm for polished scintillator crystals. Unlike polished scintillator crystals, the energy resolution in saw-cut crystals depends on DOI. It improves from 19% when DOI is in the center, to 14% with DOI at either end of the crystal, while it remains independent of DOI at 14% for polished scintillators. Similarly, we observed degradation of timing resolution in saw-cut crystals compared to polished ones. We deduce that the trade-off between DOI and energy resolution is mediated by scintillator crystal surface finishing and geometry. However, accurate extraction of DOI can be used to correct for DOI dependency of energy resolution. Based on our experimental results we conclude that saw-cut 2×2×20 mm3 LYSO crystals coupled to silicon photomultipliers (SiPMs) in dual-ended readout configuration are suitable candidates for DOI-PET applications such as positron emission mammography (PEM).