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Simulation study of wedge-shaped light guide for compensating depth-of-interaction induced timing uncertainty in Cherenkov radiator.

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Title: Simulation study of wedge-shaped light guide for compensating depth-of-interaction induced timing uncertainty in Cherenkov radiator.
Authors: Kang H; Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea., Shim HS; Interdisciplinary Program in Bioengineering, College of Engineering, Seoul National University, Seoul, Republic of Korea.; Integrated Major in Innovative Medical Science, Seoul National University, Seoul, Republic of Korea.; Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea., Yi M; Interdisciplinary Program in Bioengineering, College of Engineering, Seoul National University, Seoul, Republic of Korea.; Integrated Major in Innovative Medical Science, Seoul National University, Seoul, Republic of Korea.; Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea., Kim J; Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea., Jeong Y; Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea., Lee JS; Interdisciplinary Program in Bioengineering, College of Engineering, Seoul National University, Seoul, Republic of Korea.; Integrated Major in Innovative Medical Science, Seoul National University, Seoul, Republic of Korea.; Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea.
Source: Medical physics [Med Phys] 2026 Sep; Vol. 53 (9), pp. e70655.
Publication Type: Journal Article
Language: English
Journal Info: Publisher: John Wiley and Sons, Inc Country of Publication: United States NLM ID: 0425746 Publication Model: Print Cited Medium: Internet ISSN: 2473-4209 (Electronic) Linking ISSN: 00942405 NLM ISO Abbreviation: Med Phys Subsets: MEDLINE
Imprint Name(s): Publication: 2017- : Hoboken, NJ : John Wiley and Sons, Inc.
Original Publication: Lancaster, Pa., Published for the American Assn. of Physicists in Medicine by the American Institute of Physics.
MeSH Terms: Positron-Emission Tomography*/instrumentation , Monte Carlo Method* , Light*, Time Factors ; Uncertainty ; Photons ; Computer Simulation
Abstract: Background: Coincidence timing resolution (CTR) is a key performance factor in PET systems. Cherenkov radiation, due to its ultrafast emission on the femtosecond scale, offers potential for achieving improved timing resolution compared to traditional scintillation-based detectors. However, the inherently low photon yield in pure Cherenkov radiators makes depth-of-interaction (DOI) estimation and its associated timing uncertainty a significant challenge, especially when trying to achieve sub-30 ps CTR.
Purpose: This study aims to reduce DOI-induced timing uncertainty in Cherenkov-based PET detectors by proposing a novel wedge-shaped light guide design. The goal is to improve the CTR performance by compensating for optical path differences resulting from varying interaction depths.
Methods: A Monte Carlo simulation framework was developed to model gamma-ray interactions within a Cherenkov radiator, incorporating electron scattering and Cherenkov photon generation. Two detector geometries were compared: one with a conventional planar light guide and another with the proposed wedge-shaped light guide. The wedge design was tailored to delay early-arriving photons and synchronize photon transit times, thereby reducing time spread. The simulation tracked photon paths through the wedge and evaluated performance using metrics such as spatial resolution, timing spread, and sensitivity.
Results: Simulations demonstrated that the wedge-shaped light guide significantly reduced DOI-induced timing uncertainty-by 26.3% in a 3 mm-thick Cherenkov radiator-compared to the conventional configuration. The wedge geometry also enabled improved spatial resolution in multi-layer detector configurations. However, a trade-off with reduced sensitivity was observed. To address this, strategies such as utilizing discarded photons via refractive index manipulation and cascade detector structures were proposed.
Conclusions: The wedge-shaped light guide effectively compensates for DOI-related path length differences and enhances CTR in Cherenkov-based PET detectors. This approach opens avenues for more accurate event localization without increasing photon yield, and could serve as a building block for advanced PET systems requiring ultrafast timing performance.
(© 2026 American Association of Physicists in Medicine.)
References: Front Phys. 2022;10:. (PMID: 37220601)
Phys Med Biol. 2013 May 21;58(10):3243-57. (PMID: 23611889)
Phys Med Biol. 2024 Jan 05;69(2):. (PMID: 38091614)
Phys Med Biol. 2021 Mar 09;66(6):065019. (PMID: 33412542)
Phys Med Biol. 2020 Jan 17;65(2):025001. (PMID: 31851947)
IEEE Trans Radiat Plasma Med Sci. 2023 Mar;7(3):233-240. (PMID: 36994147)
Phys Med Biol. 2021 Sep 21;66(19):. (PMID: 34433139)
Phys Med Biol. 2019 Apr 29;64(9):095014. (PMID: 30978704)
J Nucl Med. 2020 Oct;61(10):1528-1533. (PMID: 32111684)
Phys Med Biol. 2019 Mar 29;64(7):07LT01. (PMID: 30870825)
Phys Med Biol. 2017 Jun 7;62(11):4421-4439. (PMID: 28358722)
ACS Photonics. 2025 Feb 06;12(2):1125-1136. (PMID: 39989930)
Phys Med Biol. 2020 Nov 03;65(21):215021. (PMID: 32707569)
Phys Med Biol. 2025 Jan 27;70(3):. (PMID: 39808925)
Med Phys. 2026 Sep;53(9):e70655. (PMID: 42682171)
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Phys Med Biol. 2016 Nov 7;61(21):7600-7622. (PMID: 27716640)
Med Phys. 2020 Jul;47(7):2721-2724. (PMID: 32141611)
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Nat Photonics. 2021 Dec;15(12):914-918. (PMID: 35663419)
Front Phys. 2021;9:. (PMID: 36845872)
Phys Med Biol. 2020 Jun 05;65(11):115004. (PMID: 32268304)
Phys Med Biol. 2018 Sep 19;63(18):185022. (PMID: 30129562)
IEEE Trans Biomed Circuits Syst. 2018 Dec;12(6):1401-1409. (PMID: 30113901)
EJNMMI Phys. 2016 Dec;3(1):3. (PMID: 26879863)
Grant Information: 800-20230383 Interdisciplinary Research Initiatives Program
Contributed Indexing: Keywords: Cherenkov radiation; Monte Carlo simulation; PET detector; depth‐of‐interaction; timing resolution; wedge‐shaped light guide
Entry Date(s): Date Created: 20260902 Date Completed: 20260902 Latest Revision: 20260904
Update Code: 20260904
PubMed Central ID: PMC13535723
DOI: 10.1002/mp.70655
PMID: 42682171
Database: MEDLINE
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  Data: Simulation study of wedge-shaped light guide for compensating depth-of-interaction induced timing uncertainty in Cherenkov radiator.
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  Data: <searchLink fieldCode="AU" term="%22Kang+H%22">Kang H</searchLink>; Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea.<br /><searchLink fieldCode="AU" term="%22Shim+HS%22">Shim HS</searchLink>; Interdisciplinary Program in Bioengineering, College of Engineering, Seoul National University, Seoul, Republic of Korea.; Integrated Major in Innovative Medical Science, Seoul National University, Seoul, Republic of Korea.; Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea.<br /><searchLink fieldCode="AU" term="%22Yi+M%22">Yi M</searchLink>; Interdisciplinary Program in Bioengineering, College of Engineering, Seoul National University, Seoul, Republic of Korea.; Integrated Major in Innovative Medical Science, Seoul National University, Seoul, Republic of Korea.; Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea.<br /><searchLink fieldCode="AU" term="%22Kim+J%22">Kim J</searchLink>; Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea.<br /><searchLink fieldCode="AU" term="%22Jeong+Y%22">Jeong Y</searchLink>; Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea.<br /><searchLink fieldCode="AU" term="%22Lee+JS%22">Lee JS</searchLink>; Interdisciplinary Program in Bioengineering, College of Engineering, Seoul National University, Seoul, Republic of Korea.; Integrated Major in Innovative Medical Science, Seoul National University, Seoul, Republic of Korea.; Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea.
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  Data: <searchLink fieldCode="JN" term="%220425746%22">Medical physics</searchLink> [Med Phys] 2026 Sep; Vol. 53 (9), pp. e70655.
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  Data: <i>Publication</i>: 2017- : Hoboken, NJ : John Wiley and Sons, Inc.<br /><i>Original Publication</i>: Lancaster, Pa., Published for the American Assn. of Physicists in Medicine by the American Institute of Physics.
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  Label: Abstract
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  Data: Background: Coincidence timing resolution (CTR) is a key performance factor in PET systems. Cherenkov radiation, due to its ultrafast emission on the femtosecond scale, offers potential for achieving improved timing resolution compared to traditional scintillation-based detectors. However, the inherently low photon yield in pure Cherenkov radiators makes depth-of-interaction (DOI) estimation and its associated timing uncertainty a significant challenge, especially when trying to achieve sub-30 ps CTR.<br />Purpose: This study aims to reduce DOI-induced timing uncertainty in Cherenkov-based PET detectors by proposing a novel wedge-shaped light guide design. The goal is to improve the CTR performance by compensating for optical path differences resulting from varying interaction depths.<br />Methods: A Monte Carlo simulation framework was developed to model gamma-ray interactions within a Cherenkov radiator, incorporating electron scattering and Cherenkov photon generation. Two detector geometries were compared: one with a conventional planar light guide and another with the proposed wedge-shaped light guide. The wedge design was tailored to delay early-arriving photons and synchronize photon transit times, thereby reducing time spread. The simulation tracked photon paths through the wedge and evaluated performance using metrics such as spatial resolution, timing spread, and sensitivity.<br />Results: Simulations demonstrated that the wedge-shaped light guide significantly reduced DOI-induced timing uncertainty-by 26.3% in a 3 mm-thick Cherenkov radiator-compared to the conventional configuration. The wedge geometry also enabled improved spatial resolution in multi-layer detector configurations. However, a trade-off with reduced sensitivity was observed. To address this, strategies such as utilizing discarded photons via refractive index manipulation and cascade detector structures were proposed.<br />Conclusions: The wedge-shaped light guide effectively compensates for DOI-related path length differences and enhances CTR in Cherenkov-based PET detectors. This approach opens avenues for more accurate event localization without increasing photon yield, and could serve as a building block for advanced PET systems requiring ultrafast timing performance.<br /> (© 2026 American Association of Physicists in Medicine.)
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  Label: References
  Group: RefInfo
  Data: Front Phys. 2022;10:. (PMID: <searchLink fieldCode="PM" term="%2237220601%22">37220601)</searchLink><br />Phys Med Biol. 2013 May 21;58(10):3243-57. (PMID: <searchLink fieldCode="PM" term="%2223611889%22">23611889)</searchLink><br />Phys Med Biol. 2024 Jan 05;69(2):. (PMID: <searchLink fieldCode="PM" term="%2238091614%22">38091614)</searchLink><br />Phys Med Biol. 2021 Mar 09;66(6):065019. (PMID: <searchLink fieldCode="PM" term="%2233412542%22">33412542)</searchLink><br />Phys Med Biol. 2020 Jan 17;65(2):025001. (PMID: <searchLink fieldCode="PM" term="%2231851947%22">31851947)</searchLink><br />IEEE Trans Radiat Plasma Med Sci. 2023 Mar;7(3):233-240. (PMID: <searchLink fieldCode="PM" term="%2236994147%22">36994147)</searchLink><br />Phys Med Biol. 2021 Sep 21;66(19):. (PMID: <searchLink fieldCode="PM" term="%2234433139%22">34433139)</searchLink><br />Phys Med Biol. 2019 Apr 29;64(9):095014. (PMID: <searchLink fieldCode="PM" term="%2230978704%22">30978704)</searchLink><br />J Nucl Med. 2020 Oct;61(10):1528-1533. (PMID: <searchLink fieldCode="PM" term="%2232111684%22">32111684)</searchLink><br />Phys Med Biol. 2019 Mar 29;64(7):07LT01. (PMID: <searchLink fieldCode="PM" term="%2230870825%22">30870825)</searchLink><br />Phys Med Biol. 2017 Jun 7;62(11):4421-4439. (PMID: <searchLink fieldCode="PM" term="%2228358722%22">28358722)</searchLink><br />ACS Photonics. 2025 Feb 06;12(2):1125-1136. (PMID: <searchLink fieldCode="PM" term="%2239989930%22">39989930)</searchLink><br />Phys Med Biol. 2020 Nov 03;65(21):215021. (PMID: <searchLink fieldCode="PM" term="%2232707569%22">32707569)</searchLink><br />Phys Med Biol. 2025 Jan 27;70(3):. (PMID: <searchLink fieldCode="PM" term="%2239808925%22">39808925)</searchLink><br />Med Phys. 2026 Sep;53(9):e70655. (PMID: <searchLink fieldCode="PM" term="%2242682171%22">42682171)</searchLink><br />Med Phys. 2024 Jun;51(6):4044-4055. (PMID: <searchLink fieldCode="PM" term="%2238682574%22">38682574)</searchLink><br />Phys Med Biol. 2016 Nov 7;61(21):7600-7622. (PMID: <searchLink fieldCode="PM" term="%2227716640%22">27716640)</searchLink><br />Med Phys. 2020 Jul;47(7):2721-2724. (PMID: <searchLink fieldCode="PM" term="%2232141611%22">32141611)</searchLink><br />Phys Med Biol. 2021 Nov 05;66(21):. (PMID: <searchLink fieldCode="PM" term="%2234666328%22">34666328)</searchLink><br />Nat Photonics. 2021 Dec;15(12):914-918. (PMID: <searchLink fieldCode="PM" term="%2235663419%22">35663419)</searchLink><br />Front Phys. 2021;9:. (PMID: <searchLink fieldCode="PM" term="%2236845872%22">36845872)</searchLink><br />Phys Med Biol. 2020 Jun 05;65(11):115004. (PMID: <searchLink fieldCode="PM" term="%2232268304%22">32268304)</searchLink><br />Phys Med Biol. 2018 Sep 19;63(18):185022. (PMID: <searchLink fieldCode="PM" term="%2230129562%22">30129562)</searchLink><br />IEEE Trans Biomed Circuits Syst. 2018 Dec;12(6):1401-1409. (PMID: <searchLink fieldCode="PM" term="%2230113901%22">30113901)</searchLink><br />EJNMMI Phys. 2016 Dec;3(1):3. (PMID: <searchLink fieldCode="PM" term="%2226879863%22">26879863)</searchLink>
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  Data: <i>Keywords: </i>Cherenkov radiation; Monte Carlo simulation; PET detector; depth‐of‐interaction; timing resolution; wedge‐shaped light guide
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