Generic high resolution PET detector block using 12 × 12 SiPM array

Abstract

With the advancement of the Silicon Photomultiplier (SiPM) technology, these devices are becoming the mainstream for use in high resolution PET detectors especially where the compatibility with magnetic field is critical. Large-area SiPM arrays are now widely used in high resolution PET detector modules. The challenges are emerged in the readout and timing circuitry by the increase of pixel density in the area. The application-specific integrated circuits (ASICs) are developed to readout arrays with standard anode/ cathode outputs. SiPM detection principle, which produces dark current noise in the inactive pixels, makes the multiplexing techniques more challenging rather than the PMT signals. In this work a new generic PET detector block using SiPM arrays with three outputs (anode, cathode, and fast) is presented which is suitable for applications in small animal, brain, and clinical PET imaging. The block detector accepts a 12×12 array with both standard and fast output signals with an overall detector dimension of 50×50 mm 2 . A new version of the scrambled crosswire readout (SCR) method was implemented to reduce 144 'fast outputs' to 9 tile signals and 144 standard outputs to 16 energy channels. The tile signals are also used to generate time pickoff information for timing resolution. We implemented time-to-digital converter (TDC) in Xilinx's SPARTAN6 field programmable gate array (FPGA) by using the 64-tap delay line. This low cost chip performs all required processes for position, energy, time, and interface architecture. The attached 24×24 LYSO:Ce array with 2×2×10 mm 3 pixels is imaged and pixels are resolved clearly in the room temperature. The measured energy resolution of the detector block after calibration for all crystal pixels is 12.4% at 511 keV. Also, the coincidence resolving time for two identical modules was measured at 1.85 ns.

Novel preclinical PET geometrical concept using a monolithic scintillator crystal offering concurrent enhancement in spatial resolution and detection sensitivity: a simulation study

“…Most dedicated small-animal PET scanners were designed and manufactured based on pixelated detector arrays to provide high spatial resolution. Owing to the availability of pixelated detector arrays with small detector elements, sub-millimetric spatial resolution has been achieved (Fontaine et al 2009, Prasad et al 2011, Sajedi et al 2018. However, despite the enhanced spatial resolution, PET scanners equipped with pixelated detector arrays suffer from mediocre or poor sensitivity owing to low detection efficiency of pixelated detector arrays.…”

NEMA NU‐4 2008 performance evaluation of Xtrim‐PET: A prototype SiPM‐based preclinical scanner

“…One of the most interesting features of the present scanner is the SiPM‐based detection scheme, which results in relatively good energy and timing resolution. Through employing time walk correction, a coincidence timing resolution of 1.85 ns FWHM and 4.4 ns FWTM was achieved between two identical blocks, which enables to reduce the number of detected random events, even when imaging high activities. Furthermore, the energy resolution as well as the peak to valley ratio for different bias voltages were measured by irradiating detector arrays with Ge‐68 rod sources located at 10 cm distance.…”

“…). A detailed description of the Xtrim‐PET system and readout electronics has been reported elsewhere . The overall design parameters of the system are summarized in Table .…”

“…After amplification, these analogue signals are digitized through 8 channels analog to digital converters (ADCs) with a sample rate of 50‐MHz and then are fed into the Field Programmable Gate Array (FPGA). A more detailed description can be found in REFS …”

Studies of event burst phenomenon with SiPMs in liquid nitrogen

“…Their distinct hallmark characteristics are the exceptional single photon number resolving capability and the low <1-photoelectron equivalent noise, both of which can be achieved at ambient temperature. Despite their nominally high dark count rate (DCR) of ∼MHz/cm 2 at room temperature that is generated by the thermal excitation of carries in the silicon avalanche junction, they are promising low light level photon detectors for use in science areas such as high-energy physics, nuclear medicine, PET imaging, and astronomy [1][2][3][4][5]. While in dark matter search and neutrino detection experiments, SiPMs are typically submerged and operated in cryogenic noble liquids for prompt vacuum ultraviolet (VUV) scintillation light or wavelength-shifted to the blue wavelength regime for photon detection.…”