Multiplexing Readout for Time-of-Flight (TOF) PET Detectors Using Striplines

A recent trend in PET instrumentation is the use of silicon photomultipliers (SiPMs) for high resolution and time-of-flight (TOF) detection. Due to its small size, a PET system can use a large number of SiPMs and hence effective and scalable multiplexing readout methods become important. Unfortunately, multiplexing readout generally degrades the fast timing properties necessary for TOF, especially at high channel reduction. Previously, we developed a stripline (SL)-based readout method for PET that uses a time-based multiplexing mechanism. This method maintains fast timing by design and has been successfully used for TOF PET detectors. In this article, we present a more systematic study in which we examine how two important design parameters of the readout—the number of inputs on an SL ( $n_{\mathrm {SL}}$ ) and the pathlength between adjacent input positions ( $\Delta \ell $ )—affect its detection performance properties for PET. Our result shows that up to $n_{\mathrm {SL}}=32$ the readout can achieve accurate pixel discrimination and causes little degradation in the energy resolution. The TOF resolution is compromised mildly and a coincidence resolving time on the order of 300-ps FWHM can be achieved for lutetium–yttrium oxyorthosilicate- and SiPM-based detectors. We also discuss strategies in using the readout to further reduce the number of electronic channels that a PET system would otherwise need.