HRFlexToT: A High Dynamic Range ASIC for Time-of-Flight Positron Emission Tomography

Time-of-Flight positron emission tomography scanners demand fast and efficient photo sensors and scintillators coupled to fast readout electronics. This article presents the high resolution flexible Time-over-Threshold (HRFlexToT), a 16-channel application-specific-integrated circuit for silicon photomultipliers (SiPM) anode readout manufactured using XFAB 0.18-mu m CMOS technology. The main features of the HRFlexToT are a linear Time-over-Threshold with an extended dynamic range (10 bits) for energy measurement, low power consumption (approximate to 3.5 mW/ch), and an excellent timing response. The experimental measurements show an energy linearity error of approximate to 3% and an energy resolution of about 12% at 511 keV. Single-photon time resolution measurements performed using an Fondazione Bruno Kessler (FBK) SiPM NUV-HD (4 x 4 mm(2) pixel, 40-gm cell) and a Hamamatsu SiPM 513360-3050CS are around 142 and 167 ps full width at half maximum (FWHM), respectively. Coincidence time resolution (CTR) measurements with small cross-section pixelated crystals (LSO:Ce,Ca 0.4%, 2 x 2 x 5 mm(3)) coupled to the same Hamamatsu 513360-3050CS and FBK NUV-HD sensors yield a CTR of 117 ps and 119 ps, respectively. Measurements performed with a large cross-section monolithic crystal (LFS crystal measuring 25 x 25 x 20 mm(3)) and a Hamamatsu SiPM array 513361-6050NE-04 show a CTR of 324 ps FWHM after time-walk and time-skew correction.

Automated summary

This article presents a high resolution flexible Time-over-Threshold (HRFlexToT) for silicon photomultipliers (SiPM) anode readout. Experimental measurements show good energy linearity and resolution, as well as single-photon and coincidence time resolution.