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Estimation of backscatter factor in ISO-recommended phantoms for photon beams of different beam sizes using Monte Carlo simulations.

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Title: Estimation of backscatter factor in ISO-recommended phantoms for photon beams of different beam sizes using Monte Carlo simulations.
Authors: Yadav R; Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Mumbai 400085, India., Bakshi AK; Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Mumbai 400085, India.; Homi Bhabha National Institute, Mumbai 400085, India., Sapra BK; Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Mumbai 400085, India.; Homi Bhabha National Institute, Mumbai 400085, India.
Source: Journal of radiological protection : official journal of the Society for Radiological Protection [J Radiol Prot] 2026 Aug 03; Vol. 46 (3). Date of Electronic Publication: 2026 Aug 03.
Publication Type: Journal Article
Language: English
Journal Info: Publisher: IOP Pub. Ltd Country of Publication: England NLM ID: 8809257 Publication Model: Electronic Cited Medium: Internet ISSN: 1361-6498 (Electronic) Linking ISSN: 09524746 NLM ISO Abbreviation: J Radiol Prot Subsets: MEDLINE
Imprint Name(s): Original Publication: [Bristol, UK] : IOP Pub. Ltd., [c1988-
MeSH Terms: Monte Carlo Method* , Photons* , Scattering, Radiation* , Phantoms, Imaging* , Radiometry*, Computer Simulation ; Radiation Dosage
Abstract: Backscatter factor (BSF) is a critical correction parameter in radiation dosimetry, accounting for dose enhancement due to photon scattering within irradiated media; however, systematic evaluations beyond the ISO slab phantom remain limited. In this work, BSFs were comprehensively estimated for all ISO-recommended phantoms-slab, cylindrical, pillar, and rod-over a photon energy range of 10 keV-2 MeV and multiple field sizes using the FLUKA Monte Carlo code with an air-kerma-based formalism. The results show a strong coupled dependence of BSF on photon energy and beam size, with a characteristic peak in the intermediate energy range (∼40-80 keV) and geometry-driven variations and field-size sensitivity-maximized in the slab phantom and minimized in the rod due to scattering volume constraints, while cylindrical and pillar phantoms exhibit intermediate behaviour. To extend these results to realistic irradiation conditions, a Python-based standalone tool was developed using PCHIP interpolation and fluence-weighted averaging to compute spectrum-averaged BSFs for ISO 4037 beams, diagnostic and therapeutic spectra, and user-defined spectra, demonstrating deviation within 0%-2.3% with published data. The study provides a BSF dataset across all ISO phantoms along with a validated computational framework, enabling improved accuracy in dosimeter calibration and determination of operational quantities such asHp(3) andHp(0.07). The Python-based standalone executable of the BSF software, compatible with both Windows and Linux platforms, along with its complete source code, is provided as open-access supplementary data.
(Creative Commons Attribution license.)
Contributed Indexing: Keywords: Backscatter factor; ISO recommended phantoms; ISO slab phantom; backscatter factor beam size; photon back scattering factor
Entry Date(s): Date Created: 20260722 Date Completed: 20260803 Latest Revision: 20260803
Update Code: 20260803
DOI: 10.1088/1361-6498/ae8e83
PMID: 42486140
Database: MEDLINE
FullText Text:
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PubType: Academic Journal
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IllustrationInfo
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  Label: Title
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  Data: Estimation of backscatter factor in ISO-recommended phantoms for photon beams of different beam sizes using Monte Carlo simulations.
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  Data: <searchLink fieldCode="AU" term="%22Yadav+R%22">Yadav R</searchLink>; Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Mumbai 400085, India.<br /><searchLink fieldCode="AU" term="%22Bakshi+AK%22">Bakshi AK</searchLink>; Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Mumbai 400085, India.; Homi Bhabha National Institute, Mumbai 400085, India.<br /><searchLink fieldCode="AU" term="%22Sapra+BK%22">Sapra BK</searchLink>; Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Mumbai 400085, India.; Homi Bhabha National Institute, Mumbai 400085, India.
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  Data: <searchLink fieldCode="JN" term="%228809257%22">Journal of radiological protection : official journal of the Society for Radiological Protection</searchLink> [J Radiol Prot] 2026 Aug 03; Vol. 46 (3). <i>Date of Electronic Publication: </i>2026 Aug 03.
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  Data: Journal Article
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  Data: English
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  Data: <i>Publisher: </i><searchLink fieldCode="PB" term="%22IOP+Pub%2E+Ltd%22">IOP Pub. Ltd </searchLink><i>Country of Publication: </i>England <i>NLM ID: </i>8809257 <i>Publication Model: </i>Electronic <i>Cited Medium: </i>Internet <i>ISSN: </i>1361-6498 (Electronic) <i>Linking ISSN: </i><searchLink fieldCode="IS" term="%2209524746%22">09524746 </searchLink><i>NLM ISO Abbreviation: </i>J Radiol Prot <i>Subsets: </i>MEDLINE
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  Data: <i>Original Publication</i>: [Bristol, UK] : IOP Pub. Ltd., [c1988-
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  Label: MeSH Terms
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  Data: <searchLink fieldCode="MM" term="%22Monte+Carlo+Method%22">Monte Carlo Method*</searchLink> <br /><searchLink fieldCode="MM" term="%22Photons%22">Photons*</searchLink> <br /><searchLink fieldCode="MM" term="%22Scattering%2C+Radiation%22">Scattering, Radiation*</searchLink> <br /><searchLink fieldCode="MM" term="%22Phantoms%2C+Imaging%22">Phantoms, Imaging*</searchLink> <br /><searchLink fieldCode="MM" term="%22Radiometry%22">Radiometry*</searchLink><br /><searchLink fieldCode="MH" term="%22Computer+Simulation%22">Computer Simulation</searchLink> ; <searchLink fieldCode="MH" term="%22Radiation+Dosage%22">Radiation Dosage</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Backscatter factor (BSF) is a critical correction parameter in radiation dosimetry, accounting for dose enhancement due to photon scattering within irradiated media; however, systematic evaluations beyond the ISO slab phantom remain limited. In this work, BSFs were comprehensively estimated for all ISO-recommended phantoms-slab, cylindrical, pillar, and rod-over a photon energy range of 10 keV-2 MeV and multiple field sizes using the FLUKA Monte Carlo code with an air-kerma-based formalism. The results show a strong coupled dependence of BSF on photon energy and beam size, with a characteristic peak in the intermediate energy range (∼40-80 keV) and geometry-driven variations and field-size sensitivity-maximized in the slab phantom and minimized in the rod due to scattering volume constraints, while cylindrical and pillar phantoms exhibit intermediate behaviour. To extend these results to realistic irradiation conditions, a Python-based standalone tool was developed using PCHIP interpolation and fluence-weighted averaging to compute spectrum-averaged BSFs for ISO 4037 beams, diagnostic and therapeutic spectra, and user-defined spectra, demonstrating deviation within 0%-2.3% with published data. The study provides a BSF dataset across all ISO phantoms along with a validated computational framework, enabling improved accuracy in dosimeter calibration and determination of operational quantities such asH<subscript>p</subscript>(3) andH<subscript>p</subscript>(0.07). The Python-based standalone executable of the BSF software, compatible with both Windows and Linux platforms, along with its complete source code, is provided as open-access supplementary data.<br /> (Creative Commons Attribution license.)
– Name: SubjectMinor
  Label: Contributed Indexing
  Group:
  Data: <i>Keywords: </i>Backscatter factor; ISO recommended phantoms; ISO slab phantom; backscatter factor beam size; photon back scattering factor
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  Label: Entry Date(s)
  Group: Date
  Data: <i>Date Created: </i>20260722 <i>Date Completed: </i>20260803 <i>Latest Revision: </i>20260803
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  Data: 20260803
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  Data: 10.1088/1361-6498/ae8e83
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  Label: PMID
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  Data: 42486140
PLink https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=cmedm&AN=42486140
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        Value: 10.1088/1361-6498/ae8e83
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      – Code: eng
        Text: English
    Subjects:
      – SubjectFull: Computer Simulation
        Type: general
      – SubjectFull: Radiation Dosage
        Type: general
      – SubjectFull: Monte Carlo Method
        Type: general
      – SubjectFull: Photons
        Type: general
      – SubjectFull: Scattering, Radiation
        Type: general
      – SubjectFull: Phantoms, Imaging
        Type: general
      – SubjectFull: Radiometry
        Type: general
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      – TitleFull: Estimation of backscatter factor in ISO-recommended phantoms for photon beams of different beam sizes using Monte Carlo simulations.
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            NameFull: Yadav R
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            NameFull: Bakshi AK
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            NameFull: Sapra BK
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            – D: 03
              M: 08
              Text: 2026 Aug 03
              Type: published
              Y: 2026
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              Value: 46
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              Value: 3
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            – TitleFull: Journal of radiological protection : official journal of the Society for Radiological Protection
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