Hybrid charge division multiplexing method for silicon photomultiplier based PET detectors

Abstract

Silicon photomultiplier (SiPM) is widely utilized in various positron emission tomography (PET) detectors and systems. However, the individual recording of SiPM output signals is still challenging owing to the high granularity of the SiPM; thus, charge division multiplexing is commonly used in PET detectors. Resistive charge division method is well established for reducing the number of output channels in conventional multi-channel photosensors, but it degrades the timing performance of SiPM-based PET detectors by yielding a large resistor-capacitor (RC) constant. Capacitive charge division method, on the other hand, yields a small RC constant and provides a faster timing response than the resistive method, but it suffers from an output signal undershoot. Therefore, in this study, we propose a hybrid charge division method which can be implemented by cascading the parallel combination of a resistor and a capacitor throughout the multiplexing network. In order to compare the performance of the proposed method with the conventional methods, a 16-channel Hamamatsu SiPM (S11064-050P) was coupled with a 4 × 4 LGSO crystal block (3 × 3 × 20 mm) and a 9 × 9 LYSO crystal block (1.2 × 1.2 × 10 mm). In addition, we tested a time-over-threshold (TOT) readout using the digitized position signals to further demonstrate the feasibility of the time-based readout of multiplexed signals based on the proposed method. The results indicated that the proposed method exhibited good energy and timing performance, thus inheriting only the advantages of conventional resistive and capacitive methods. Moreover, the proposed method showed excellent pulse shape uniformity that does not depend on the position of the interacted crystal. Accordingly, we can conclude that the hybrid charge division method is useful for effectively reducing the number of output channels of the SiPM array.

Advances in Detector Instrumentation for PET

“…Nevertheless, this multiplexing scheme provides the advantage of reducing the number of output channels and the overall complexity of a system but typically affects key performance parameters such as spatial, timing, and energy resolutions and count-rate performance. An alternative approach is to use capacitive multiplexing schemes or a hybrid multiplexing scheme in which resistive and capacitive networks are used in parallel (21). These different types of multiplexing schemes have a goal of improving one or more key parameters and can be adopted accordingly depending on the application.…”

Silicon photomultiplier signal readout and multiplexing techniques for positron emission tomography: a review

“…The twoterminal signals of each row are then fed respectively into two 1D resistor chains arranged in a column direction. The split signals by the resister chains in the column direction are collected by four amplifiers at the corner of the multiplexing To further improve the performance of the DPC, Park et al [134] investigated and demonstrated a hybrid DPC implemented by cascading the parallel combination of a resistor and capacitor throughout the DPC network (Fig. 6b).…”

Single-line multi-voltage threshold method for scintillation detectors

“…However, the high granularity of SiPMs due to their compact size has increased the number of output channels and the complexity of signal readout and data acquisition electronics. To overcome these problems, several analog signal multiplexing techniques have been proposed [15][16][17][18][19][20][21][22]. However, many advanced PET detectors, such as depth of interaction (DOI)-encoding detectors that use light distribution information [23,24], require SiPM signal readout and recording with no or only moderate analog signal multiplexing.…”

“…In addition, highly integrated TDCs can be implemented using field-programmable gate arrays (FPGAs) [36][37][38][39]. However, the simple TOT method using a single threshold suffers from inferior energy linearity compared with ADC-based measurements [17,34,40]. Therefore, several approaches have been proposed to overcome the limitations of the TOT method.…”