{"title":"A Scalable Dynamic TOT Circuit for a 100 ps TOF-PET Detector Design to Improve Energy Linearity and Dynamic Range","authors":"Shirin Pourashraf;Joshua W. Cates;Craig S. Levin","doi":"10.1109/TRPMS.2023.3344399","DOIUrl":null,"url":null,"abstract":"This article focuses on adapting linearization strategies for annihilation photon energy measurement for a time-of-flight (TOF) positron emission tomography (PET) system that achieves \n<inline-formula> <tex-math>$\\sim 100$ </tex-math></inline-formula>\n picosecond (ps) full-width at half maximum (FWHM) coincidence time resolution (CTR). We have adapted the method of dynamic TOT (DynTOT) for our scalable TOF-PET detector readout electronics to linearize the energy spectra while maintaining \n<inline-formula> <tex-math>$\\sim 100$ </tex-math></inline-formula>\n ps FWHM CTR. The linear response of the resulting DynTOT circuit facilitates improved energy performance compared with conventional time-over-threshold (TOT). Our detector design has the capability to position the 3-D coordinates of one or more 511-keV photon interactions. To facilitate this goal, DynTOT’s linearity across the entire energy range enables accurate measurement of low-energy interactions that is required for more accurate positioning of intercrystal scatter events. This DynTOT block is implemented by off-the-shelf discrete components and consumes only 11 mW power per detector layer unit design comprising 24:1 multiplexed energy and timing channels. We first validated the performance of DynTOT using single \n<inline-formula> <tex-math>$3\\times 3\\times10$ </tex-math></inline-formula>\n mm3 LGSO scintillation crystals side-coupled to arrays of three \n<inline-formula> <tex-math>$3\\times3$ </tex-math></inline-formula>\n mm2 SiPMs which achieved 511-keV photopeak energy resolutions of 13.6 ± 0.4%, 13.0 ± 0.8%, and 17.1 ± 0.6% for conventional pulse height, DynTOT, and conventional TOT methods, respectively. Then, we stretched by roughly 7-fold the DynTOT digital pulses (energy) generated from side-coupling \n<inline-formula> <tex-math>$2\\times4$ </tex-math></inline-formula>\n array of \n<inline-formula> <tex-math>$3\\times 3\\times10$ </tex-math></inline-formula>\n mm3 crystals to 24 SiPMs, and achieved 511-keV photopeak energy resolutions of 11.8 ± 0.7% with a dynamic range from less than 60 to 1274 keV, making that suitable for methods of accurate 3-D positioning of intercrystal-scatter interactions. Moreover, CTR with a highly multiplexed timing circuit was measured using these extended DynTOT pulses for energy gating, resulting in an average 108 ± 1.3 ps FWHM CTR.","PeriodicalId":46807,"journal":{"name":"IEEE Transactions on Radiation and Plasma Medical Sciences","volume":null,"pages":null},"PeriodicalIF":4.6000,"publicationDate":"2023-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"IEEE Transactions on Radiation and Plasma Medical Sciences","FirstCategoryId":"1085","ListUrlMain":"https://ieeexplore.ieee.org/document/10365584/","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING","Score":null,"Total":0}
引用次数: 0
Abstract
This article focuses on adapting linearization strategies for annihilation photon energy measurement for a time-of-flight (TOF) positron emission tomography (PET) system that achieves
$\sim 100$
picosecond (ps) full-width at half maximum (FWHM) coincidence time resolution (CTR). We have adapted the method of dynamic TOT (DynTOT) for our scalable TOF-PET detector readout electronics to linearize the energy spectra while maintaining
$\sim 100$
ps FWHM CTR. The linear response of the resulting DynTOT circuit facilitates improved energy performance compared with conventional time-over-threshold (TOT). Our detector design has the capability to position the 3-D coordinates of one or more 511-keV photon interactions. To facilitate this goal, DynTOT’s linearity across the entire energy range enables accurate measurement of low-energy interactions that is required for more accurate positioning of intercrystal scatter events. This DynTOT block is implemented by off-the-shelf discrete components and consumes only 11 mW power per detector layer unit design comprising 24:1 multiplexed energy and timing channels. We first validated the performance of DynTOT using single
$3\times 3\times10$
mm3 LGSO scintillation crystals side-coupled to arrays of three
$3\times3$
mm2 SiPMs which achieved 511-keV photopeak energy resolutions of 13.6 ± 0.4%, 13.0 ± 0.8%, and 17.1 ± 0.6% for conventional pulse height, DynTOT, and conventional TOT methods, respectively. Then, we stretched by roughly 7-fold the DynTOT digital pulses (energy) generated from side-coupling
$2\times4$
array of
$3\times 3\times10$
mm3 crystals to 24 SiPMs, and achieved 511-keV photopeak energy resolutions of 11.8 ± 0.7% with a dynamic range from less than 60 to 1274 keV, making that suitable for methods of accurate 3-D positioning of intercrystal-scatter interactions. Moreover, CTR with a highly multiplexed timing circuit was measured using these extended DynTOT pulses for energy gating, resulting in an average 108 ± 1.3 ps FWHM CTR.