Achieving reliable coincidence resolving time measurement of PET detectors using multichannel waveform digitizer based on DRS4 chip

Abstract

Coincidence resolving time (CRT) is one of the most important physical-performance measures for positron emission tomography (PET), as reconstruction with accurate time-of-flight information enhances the lesion detectability in patient studies. Accordingly, various PET detector designs and high-performance front-end readout circuits have been actively investigated to improve timing performance. The resulting PET detectors are often evaluated using multichannel waveform digitizers for versatile data analysis of the output signals. However, we have found that inappropriate data acquisition (DAQ) using a multichannel waveform digitizer based on the domino-ring-sampler 4 (DRS4) chip can lead to a considerable error when determining CRT. To address this issue, we performed CRT measurements using a pair of Hamamatsu R9800 photomultiplier tube based PET detectors. Then, considering intra- and inter-chip sampling, we employed four different combinations of input channels into the CAEN DT5742B waveform digitizer and obtained 2D CRT maps according to the leading-edge discriminator threshold for assessing each DAQ scheme. The intra-chip CRT measurement exhibited unusual streak patterns in the 2D CRT map and yielded the artificially-low CRT information in PET detector pairs, whereas the inter-chip CRT measurement provided the reliable estimation of timing resolution. Further, we could prevent the high-frequency signal crosstalk among input channels within the DRS4 chip using the inter-chip CRT measurement. We expect that our findings will also be useful for achieving the reliable CRT measurements when using other single-chip-based multichannel waveform digitizers.

Depth‐of‐interaction positron emission tomography detector with 45° tilted silicon photomultipliers using dual‐ended signal readout

“…Inter-chip measurement was conducted to eliminate the highfrequency interference between adjacent DAQ channels within the DRS4 chip. 39…”

“…The trigger value, which is a constant fraction of the peak height of the time signal, was swept during CTR measurement to achieve optimal timing performance in our measurement setup. Inter‐chip measurement was conducted to eliminate the high‐frequency interference between adjacent DAQ channels within the DRS4 chip 39 …”

A novel strategy to develop deep learning for image super-resolution using original ultra-high-resolution computed tomography images of lung as training dataset

“…The ultra-high-quality image constructed by SR-DL contains less image noise compared to conventional U-HRCT images. Many previous studies report that super-resolution and image noise reduction can be achieved simultaneously [ 10 , 13 – 16 ]. While U-HRCT shows superior image quality, the U-HRCT image obtained from inflated fixed cadaveric human lungs does not show lung microstructures as expected from its high spatial resolution.…”

Physics and technology of time-of-flight PET detectors

“…The possibility to digitize the waveforms of all detector pulses was mentioned already. Compact and affordable digitizers with sampling rates >1 GHz exist that facilitate multichannel implementation of this approach (Cho et al 2011, Ronzhin et al 2013, Ashmanskas et al 2014, Park et al 2018. Time-multiplexing can be used to reduce costs, but leads to an increased DCR on the multiplexed channel (Grant and Levin 2015, Kim et al 2016, Bieniosek et al 2016a, Won et al 2016a.…”