Optical delay encoding for fast timing and detector signal multiplexing in PET

Abstract

Purpose: The large number of detector channels in modern positron emission tomography (PET) scanners poses a challenge in terms of readout electronics complexity. Multiplexing schemes are typically implemented to reduce the number of physical readout channels, but often result in performance degradation. Novel methods of multiplexing in PET must be developed to avoid this data degradation. The preservation of fast timing information is especially important for time-of-flight PET. Methods: A new multiplexing scheme based on encoding detector interaction events with a series of extremely fast overlapping optical pulses with precise delays is demonstrated in this work. Encoding events in this way potentially allows many detector channels to be simultaneously encoded onto a single optical fiber that is then read out by a single digitizer. A two channel silicon photomultiplier-based prototype utilizing this optical delay encoding technique along with dual threshold time-over-threshold is demonstrated. Results: The optical encoding and multiplexing prototype achieves a coincidence time resolution of 160 ps full width at half maximum (FWHM) and an energy resolution of 13.1% FWHM at 511 keV with 3 × 3 × 5 mm 3 LYSO crystals. All interaction information for both detectors, including timing, energy, and channel identification, is encoded onto a single optical fiber with little degradation. Conclusions: Optical delay encoding and multiplexing technology could lead to time-of-flight PET scanners with fewer readout channels and simplified data acquisition systems. C 2015 American Association of Physicists in Medicine. [http://dx

Performance characteristic evaluation of a bismuth germanate-based high-sensitivity 5-ring discovery image quality positron emission tomography/computed tomography system as per National Electrical Manufacturers Association NU 2-2012

“…This technique has introduced a penalty function which acts as a noise suppression term during the iterations. [17,20,21] Q. Clear algorithm has improvised and implemented a relatively different penalty function.…”

“…[17] This penalty is a function of the difference between neighboring voxels and a function of their sum. [17][18][19][20][21][22] This penalty is controlled by a penalization factor (termed β), which is the only user-input variable to the algorithm. Penalizing factor β = 350, prescribed by vendor is used in our study for image reconstruction by Q.…”

Physics and technology of time-of-flight PET detectors

“…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. At the time of writing, waveform sampling of individual events is mostly used in research setups.…”