A multiplexed TOF and DOI capable PET detector using a binary position sensitive network

Abstract

Time of flight (TOF) and depth of interaction (DOI) capabilities can significantly enhance the quality and uniformity of positron emission tomography (PET) images. Many proposed TOF/DOI PET detectors require complex readout systems using additional photosensors, active cooling, or waveform sampling. This work describes a high performance, low complexity, room temperature TOF/DOI PET module. The module uses multiplexed timing channels to significantly reduce the electronic readout complexity of the PET detector while maintaining excellent timing, energy, and position resolution. DOI was determined using a two layer light sharing scintillation crystal array with a novel binary position sensitive network. A 20mm effective thickness LYSO crystal array with four 3mm × 3mm silicon photomultipliers (SiPM) read out by a single timing channel, one energy channel and two position channels achieved a full width half maximum (FWHM) coincidence time resolution of 180 ± 2ps with 10mm of DOI resolution and 11% energy resolution. With sixteen 3mm × 3mm SiPMs read out by a single timing channel, one energy channel and four position channels a coincidence time resolution 204 ± 1ps was achieved with 10mm of DOI resolution and 15% energy resolution. The methods presented here could significantly simplify the construction of high performance TOF/DOI PET detectors.

Time of Flight in Perspective: Instrumental and Computational Aspects of Time Resolution in Positron Emission Tomography

“…This warrants research on new detector geometries that minimize optical transfer time dispersion and/or enable DOI-correction of timestamps (which can be referred to as time resolution recovery). Some examples applicable to long crystals are dual-sided readout [201], side readout [202], phoswich approaches [203,204], and various forms of inter-crystal light sharing [205][206][207][208][209][210][211][212].…”

Multiplexed imaging for diagnosis and therapy

“…Despite this limitation, dual-tracer SPECT imaging is feasible using 201 Tl or 111 In in healthy volunteers and in diverse disease settings, and including brain imaging, cardiac imaging and cancer imaging 166,[168][169][170][171] . Improved scanner technology 172 and kinetic analysis also promulgate simultaneous dual-isotope imaging in PET, as demonstrated for single-scan dual-tracer (staggered injection of FDG and FLT; 120 min of scan time) studies in patients with primary brain tumours 173 . In general, however, near-simultaneous (two tracer injections performed within a small, defined time window) and sequential imaging of multiple PET isotopes (2 or 3 scans within one day) have been a mainstay in pharmacokinetic studies of labelled cancer-drug candidates 174,175 and validation of PET tracers 113,176 .…”

Proposal for a PET scanner with 4π formula steradian span

“…To avoid it, we must use an impedance with enough resistance to minimize the coupling of the network elements. There are some other solutions used for detecting the position of the radiation event apart from the charge distribution network [59], [60]. These are great technical solutions, however they prove quite challenging to scale up as they do not offer a level of multiplexing as high as the methods presented before.…”

“…Meaning we are actually interconnecting several photomultipliers, this increases the charge seen by the electronics and affects the position, energy and timing resolution we are able to achieve. For this reason some authors have proposed other "non conventional" encoding schemes [113], [114], [115]. These methods however might not probe optimal for our design, since we plan on using very small crystals and these methods have all used 3x3 mm 2 crystals, leading to one to one coupling schemes, it is important to point out that on [113] the authors also include DOI information.…”

“…For this reason some authors have proposed other "non conventional" encoding schemes [113], [114], [115]. These methods however might not probe optimal for our design, since we plan on using very small crystals and these methods have all used 3x3 mm 2 crystals, leading to one to one coupling schemes, it is important to point out that on [113] the authors also include DOI information. We considered different multiplexing schemes and simulated how some of them might look like.…”