Development of a multiplexed readout with high position resolution for positron emission tomography

Abstract

Detector signals for positron emission tomography (PET) are commonly multiplexed to reduce the number of digital processing channels so that the system can remain cost effective while also maintaining imaging performance. In this work, a multiplexed readout combining Anger position estimation algorithm and position decoder circuit (PDC) was developed to reduce the number of readout channels by a factor of 24, 96-to-4. The data acquisition module consisted of a TDC (50ps resolution), 4-channel ADCs (12bit, 105MHz sampling rate), 2GB SDRAM and USB3.0. The performance of the multiplexed readout was assessed with a high-resolution PET detector block composed of 2×3 detector modules, each consisting of an 8×8 array of 1.52×1.52×6mm3 LYSO, a 4×4 array of 3×3mm2 silicon photomultiplier (SiPM) and 13.4×13.4mm2 light guide with 0.7mm thickness. The acquired flood histogram showed that all 384 crystals could be resolved. The average energy resolution at 511keV was 13.7±1.6% full-width-at-half-maximum (FWHM) and the peak-to-valley ratios of the flood histogram on the horizontal and vertical lines were 18.8±0.8 and 22.8±1.3, respectively. The coincidence resolving time of a pair of detector blocks was 6.2ns FWHM. The reconstructed phantom image showed that rods down to a diameter of 1.6mm could be resolved. The results of this study indicate that the multiplexed readout would be useful in developing a PET with a spatial resolution less than the pixel size of the photosensor, such as a SiPM array.