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Sensitivity analysis of fluorescent nuclear track detectors for fast and high‐energy mono‐energetic neutron dosimetry.

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Title: Sensitivity analysis of fluorescent nuclear track detectors for fast and high‐energy mono‐energetic neutron dosimetry.
Authors: Schmidt, Stefan1,2,3,4,5 (AUTHOR) stefan.schmidt@dkfz.de, Christensen, Jeppe B.6 (AUTHOR), Lutz, Benjamin7 (AUTHOR), Stabilini, Alberto6 (AUTHOR), Yukihara, Eduardo G.6 (AUTHOR), Vedelago, José1,2,3 (AUTHOR)
Source: Medical Physics. Jul2025, Vol. 52 Issue 7, p1-12. 12p.
Subjects: Fast neutrons, Nuclear track detectors, Sensitivity analysis, Monte Carlo method, Microdosimetry
Abstract: Background: In ion beam radiotherapy, treatment radiation fields are inevitably contaminated with secondary neutrons. The energies of these neutrons can reach several hundreds of MeV. Fluorescent nuclear track detectors (FNTDs) offer a promising solution for dosimetry of fast and high‐energy neutrons, particularly given their low linear energy transfer in water (LET) detection threshold. Purpose: This study presents an experimental FNTD sensitivity analysis in six fast mono‐energetic neutron fields, comparing the response to poly allyl diglycol carbonate (PADC) neutron detectors, and investigates the feasibility of estimating ambient dose equivalent for neutrons, H∗$H^{*}$(10). Moreover, it investigates the impact of converter thickness on the detector signal for both fast and high‐energy neutrons and analyzes the resulting differences in signal. Methods: FNTDs and PADCs were exposed to mono‐energetic neutron fields with energies of 1.2 MeV, 2.5 MeV, 5 MeV, 6.5 MeV, 14.8 MeV, and 19 MeV and evaluated based on the track density. The H∗$H^{*}$(10) values for FNTDs were determined by applying energy calibration factors, k(E)$k(E)$, which were determined through Monte Carlo (MC) simulations. The benchmarked MC model is employed to investigate the sensitivity of FNTDs to high‐energy neutrons up to 200 MeV for various polyethylene (PE) converter thicknesses and to analyze the detector signal, including the particle type and the recoil proton LET. Results: The sensitivity values revealed an energy dependence for FNTDs, with variations by a factor of up to 23, whereas PADC detectors showed a smaller variation, ranging from 3 to 12. Accurate H∗$H^{*}$(10) estimation can be achieved employing MC‐derived k(E)$k(E)$ factors, with deviations not exceeding 10%$10\, \%$. The sensitivity values increased almost continuously up to 200MeV$200 \,\mathrm{MeV}$ for PE converter thicknesses above 2mm$2 \,\mathrm{mm}$, whereas plateaued for thinner PE converters above 10 MeV to 15 MeV. For neutrons above 20MeV$20 \,\mathrm{MeV}$, the generated fragments are deuterons, tritons and 4He$^{4}{\rm He}$, which constitutes up to 15%$15 \,\%$ or more of the total fluence in a 150MeV$150 \,\mathrm{MeV}$ neutron field. The recoil proton LET dropped from approximately 47keVμm−1$47\, \mathrm{keV}\,{\umu}{\mathrm{m}}^{-1}$ to nearly one order of magnitude less between 1.2 MeV and 19 MeV, with an average LET of approximately 2keVμm−1$2\, \mathrm{keV}\,{\umu}{\mathrm{m}}^{-1}$ at 150MeV$150 \,\mathrm{MeV}$. Conclusions: This study compares FNTD and PADC detector sensitivities, demonstrating a notable energy and converter thickness dependence for FNTDs, which is essential for precise dosimetry. Accurate H∗$H^{*}$(10) values for fast mono‐energetic neutrons up to 19MeV$19 \,\mathrm{MeV}$ were determined utilizing MC simulations. A benchmarked MC model for fast neutrons was then applied to analyze the FNTD signal for high‐energy neutrons. [ABSTRACT FROM AUTHOR]
Copyright of Medical Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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Items – Name: Title
  Label: Title
  Group: Ti
  Data: Sensitivity analysis of fluorescent nuclear track detectors for fast and high‐energy mono‐energetic neutron dosimetry.
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  Data: <searchLink fieldCode="AR" term="%22Schmidt%2C+Stefan%22">Schmidt, Stefan</searchLink><relatesTo>1,2,3,4,5</relatesTo> (AUTHOR)<i> stefan.schmidt@dkfz.de</i><br /><searchLink fieldCode="AR" term="%22Christensen%2C+Jeppe+B%2E%22">Christensen, Jeppe B.</searchLink><relatesTo>6</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Lutz%2C+Benjamin%22">Lutz, Benjamin</searchLink><relatesTo>7</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Stabilini%2C+Alberto%22">Stabilini, Alberto</searchLink><relatesTo>6</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Yukihara%2C+Eduardo+G%2E%22">Yukihara, Eduardo G.</searchLink><relatesTo>6</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Vedelago%2C+José%22">Vedelago, José</searchLink><relatesTo>1,2,3</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Medical+Physics%22">Medical Physics</searchLink>. Jul2025, Vol. 52 Issue 7, p1-12. 12p.
– Name: Subject
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  Data: <searchLink fieldCode="DE" term="%22Fast+neutrons%22">Fast neutrons</searchLink><br /><searchLink fieldCode="DE" term="%22Nuclear+track+detectors%22">Nuclear track detectors</searchLink><br /><searchLink fieldCode="DE" term="%22Sensitivity+analysis%22">Sensitivity analysis</searchLink><br /><searchLink fieldCode="DE" term="%22Monte+Carlo+method%22">Monte Carlo method</searchLink><br /><searchLink fieldCode="DE" term="%22Microdosimetry%22">Microdosimetry</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Background: In ion beam radiotherapy, treatment radiation fields are inevitably contaminated with secondary neutrons. The energies of these neutrons can reach several hundreds of MeV. Fluorescent nuclear track detectors (FNTDs) offer a promising solution for dosimetry of fast and high‐energy neutrons, particularly given their low linear energy transfer in water (LET) detection threshold. Purpose: This study presents an experimental FNTD sensitivity analysis in six fast mono‐energetic neutron fields, comparing the response to poly allyl diglycol carbonate (PADC) neutron detectors, and investigates the feasibility of estimating ambient dose equivalent for neutrons, H∗$H^{*}$(10). Moreover, it investigates the impact of converter thickness on the detector signal for both fast and high‐energy neutrons and analyzes the resulting differences in signal. Methods: FNTDs and PADCs were exposed to mono‐energetic neutron fields with energies of 1.2 MeV, 2.5 MeV, 5 MeV, 6.5 MeV, 14.8 MeV, and 19 MeV and evaluated based on the track density. The H∗$H^{*}$(10) values for FNTDs were determined by applying energy calibration factors, k(E)$k(E)$, which were determined through Monte Carlo (MC) simulations. The benchmarked MC model is employed to investigate the sensitivity of FNTDs to high‐energy neutrons up to 200 MeV for various polyethylene (PE) converter thicknesses and to analyze the detector signal, including the particle type and the recoil proton LET. Results: The sensitivity values revealed an energy dependence for FNTDs, with variations by a factor of up to 23, whereas PADC detectors showed a smaller variation, ranging from 3 to 12. Accurate H∗$H^{*}$(10) estimation can be achieved employing MC‐derived k(E)$k(E)$ factors, with deviations not exceeding 10%$10\, \%$. The sensitivity values increased almost continuously up to 200MeV$200 \,\mathrm{MeV}$ for PE converter thicknesses above 2mm$2 \,\mathrm{mm}$, whereas plateaued for thinner PE converters above 10 MeV to 15 MeV. For neutrons above 20MeV$20 \,\mathrm{MeV}$, the generated fragments are deuterons, tritons and 4He$^{4}{\rm He}$, which constitutes up to 15%$15 \,\%$ or more of the total fluence in a 150MeV$150 \,\mathrm{MeV}$ neutron field. The recoil proton LET dropped from approximately 47keVμm−1$47\, \mathrm{keV}\,{\umu}{\mathrm{m}}^{-1}$ to nearly one order of magnitude less between 1.2 MeV and 19 MeV, with an average LET of approximately 2keVμm−1$2\, \mathrm{keV}\,{\umu}{\mathrm{m}}^{-1}$ at 150MeV$150 \,\mathrm{MeV}$. Conclusions: This study compares FNTD and PADC detector sensitivities, demonstrating a notable energy and converter thickness dependence for FNTDs, which is essential for precise dosimetry. Accurate H∗$H^{*}$(10) values for fast mono‐energetic neutrons up to 19MeV$19 \,\mathrm{MeV}$ were determined utilizing MC simulations. A benchmarked MC model for fast neutrons was then applied to analyze the FNTD signal for high‐energy neutrons. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Medical Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1002/mp.17799
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      – Code: eng
        Text: English
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        PageCount: 12
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      – SubjectFull: Fast neutrons
        Type: general
      – SubjectFull: Nuclear track detectors
        Type: general
      – SubjectFull: Sensitivity analysis
        Type: general
      – SubjectFull: Monte Carlo method
        Type: general
      – SubjectFull: Microdosimetry
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      – TitleFull: Sensitivity analysis of fluorescent nuclear track detectors for fast and high‐energy mono‐energetic neutron dosimetry.
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              M: 07
              Text: Jul2025
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              Y: 2025
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