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Monte Carlo study of air ionization by X-ray photons and backscattering under diagnostic conditions using the developed Irradose code.

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Title: Monte Carlo study of air ionization by X-ray photons and backscattering under diagnostic conditions using the developed Irradose code.
Authors: El Basraoui O; Laboratory of Condensed Matter and Interdisciplinary Sciences, Mohammed V University in Rabat, Rabat, Morocco., Qassimi O; Laboratory of Condensed Matter and Interdisciplinary Sciences, Mohammed V University in Rabat, Rabat, Morocco., Yahyaoui C; Laboratory of Condensed Matter and Interdisciplinary Sciences, Mohammed V University in Rabat, Rabat, Morocco., El Amri L; Laboratory of Condensed Matter and Interdisciplinary Sciences, Mohammed V University in Rabat, Rabat, Morocco., Tahiri N; Laboratory of Condensed Matter and Interdisciplinary Sciences, Mohammed V University in Rabat, Rabat, Morocco., El Bounagui O; Laboratory of Condensed Matter and Interdisciplinary Sciences, Mohammed V University in Rabat, Rabat, Morocco. elbounagui@gmail.com.
Source: Radiological physics and technology [Radiol Phys Technol] 2026 Sep; Vol. 19 (3), pp. 1141-1152. Date of Electronic Publication: 2026 Jul 13.
Publication Type: Journal Article
Language: English
Journal Info: Publisher: Springer Japan Country of Publication: Japan NLM ID: 101467995 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1865-0341 (Electronic) Linking ISSN: 18650333 NLM ISO Abbreviation: Radiol Phys Technol Subsets: MEDLINE
Imprint Name(s): Original Publication: Tokyo : Springer Japan
MeSH Terms: Monte Carlo Method* , Photons* , Scattering, Radiation* , Air* , Air Ionization*, Phantoms, Imaging ; X-Rays
Abstract: Irradiation of air by X-rays, particularly during diagnostic and medical imaging procedures, induces a temporary ionization of its constituents and may lead to the formation of reactive species such as O₂+, O₂- and O₂2⁻. This study analyzes photon transport as well as scattering and backscattering phenomena in air and tissue-equivalent media, in order to evaluate dose, energy, and angular distributions. A Monte Carlo code named Irradose has been developed to simulate these processes in cylindrical geometries containing air, an HCNO phantom representing the patient, and an aqueous medium. The model was validated by comparison with the PHITS and Geant4 codes, showing good agreement with deviations below 5%. The results highlight a progressive attenuation of the beam dose in air between the source and the phantom, estimated at 1.2%. They also show a higher dose deposition in the HCNO phantom. Backscatter from this medium contributes significantly to the secondary photon field in air, with a maximum of 14.62% at 0.15 MeV and a dominant angular distribution around 2.4 rad. The ionic species O₂+, O₂- and O₂2- are discussed, as well as the limitations of this work and the associated perspectives.
(© 2026. The Author(s), under exclusive licence to Japanese Society of Radiological Technology and Japan Society of Medical Physics.)
Competing Interests: Declarations. Conflicts of interest: The authors declare that they have no conflict of interest. Ethics approval: This study is based on numerical simulations and computational modeling of X-ray–induced air ionization under clinical radiological conditions. No human subjects, biological samples, or direct clinical interventions were involved. Therefore, ethical approval was not required. Informed consent: This study did not involve human participants or patient-specific clinical data. Therefore, informed consent was not required.
References: Research (Wash D C). 2021 Dec 26;2021:9892152. (PMID: 35028585)
Commun Chem. 2021 Apr 8;4(1):49. (PMID: 36697542)
Front Public Health. 2020 Dec 15;8:601711. (PMID: 33384980)
Cureus. 2024 Dec 3;16(12):e75054. (PMID: 39749071)
Indian J Radiol Imaging. 2025 Aug 12;36(3):334-344. (PMID: 42344198)
Proc Jpn Acad Ser B Phys Biol Sci. 2017;93(6):399-421. (PMID: 28603211)
Contributed Indexing: Keywords: Air ionization; Backscatter flux; HCNO phantom; Monte Carlo simulation; Radiation transport
Entry Date(s): Date Created: 20260713 Date Completed: 20260905 Latest Revision: 20261008
Update Code: 20261008
DOI: 10.1007/s12194-026-01094-2
PMID: 42440061
Database: MEDLINE
FullText Text:
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Items – Name: Title
  Label: Title
  Group: Ti
  Data: Monte Carlo study of air ionization by X-ray photons and backscattering under diagnostic conditions using the developed Irradose code.
– Name: Author
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  Data: <searchLink fieldCode="AU" term="%22El+Basraoui+O%22">El Basraoui O</searchLink>; Laboratory of Condensed Matter and Interdisciplinary Sciences, Mohammed V University in Rabat, Rabat, Morocco.<br /><searchLink fieldCode="AU" term="%22Qassimi+O%22">Qassimi O</searchLink>; Laboratory of Condensed Matter and Interdisciplinary Sciences, Mohammed V University in Rabat, Rabat, Morocco.<br /><searchLink fieldCode="AU" term="%22Yahyaoui+C%22">Yahyaoui C</searchLink>; Laboratory of Condensed Matter and Interdisciplinary Sciences, Mohammed V University in Rabat, Rabat, Morocco.<br /><searchLink fieldCode="AU" term="%22El+Amri+L%22">El Amri L</searchLink>; Laboratory of Condensed Matter and Interdisciplinary Sciences, Mohammed V University in Rabat, Rabat, Morocco.<br /><searchLink fieldCode="AU" term="%22Tahiri+N%22">Tahiri N</searchLink>; Laboratory of Condensed Matter and Interdisciplinary Sciences, Mohammed V University in Rabat, Rabat, Morocco.<br /><searchLink fieldCode="AU" term="%22El+Bounagui+O%22">El Bounagui O</searchLink>; Laboratory of Condensed Matter and Interdisciplinary Sciences, Mohammed V University in Rabat, Rabat, Morocco. elbounagui@gmail.com.
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  Data: <searchLink fieldCode="JN" term="%22101467995%22">Radiological physics and technology</searchLink> [Radiol Phys Technol] 2026 Sep; Vol. 19 (3), pp. 1141-1152. <i>Date of Electronic Publication: </i>2026 Jul 13.
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  Data: Journal Article
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  Data: <i>Publisher: </i><searchLink fieldCode="PB" term="%22Springer+Japan%22">Springer Japan </searchLink><i>Country of Publication: </i>Japan <i>NLM ID: </i>101467995 <i>Publication Model: </i>Print-Electronic <i>Cited Medium: </i>Internet <i>ISSN: </i>1865-0341 (Electronic) <i>Linking ISSN: </i><searchLink fieldCode="IS" term="%2218650333%22">18650333 </searchLink><i>NLM ISO Abbreviation: </i>Radiol Phys Technol <i>Subsets: </i>MEDLINE
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  Data: <i>Original Publication</i>: Tokyo : Springer Japan
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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="%22Air%22">Air*</searchLink> <br /><searchLink fieldCode="MM" term="%22Air+Ionization%22">Air Ionization*</searchLink><br /><searchLink fieldCode="MH" term="%22Phantoms%2C+Imaging%22">Phantoms, Imaging</searchLink> ; <searchLink fieldCode="MH" term="%22X-Rays%22">X-Rays</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Irradiation of air by X-rays, particularly during diagnostic and medical imaging procedures, induces a temporary ionization of its constituents and may lead to the formation of reactive species such as O₂<superscript>+</superscript>, O₂<superscript>-</superscript> and O₂<superscript>2</superscript>⁻. This study analyzes photon transport as well as scattering and backscattering phenomena in air and tissue-equivalent media, in order to evaluate dose, energy, and angular distributions. A Monte Carlo code named Irradose has been developed to simulate these processes in cylindrical geometries containing air, an HCNO phantom representing the patient, and an aqueous medium. The model was validated by comparison with the PHITS and Geant4 codes, showing good agreement with deviations below 5%. The results highlight a progressive attenuation of the beam dose in air between the source and the phantom, estimated at 1.2%. They also show a higher dose deposition in the HCNO phantom. Backscatter from this medium contributes significantly to the secondary photon field in air, with a maximum of 14.62% at 0.15 MeV and a dominant angular distribution around 2.4 rad. The ionic species O₂<superscript>+</superscript>, O₂<superscript>-</superscript> and O₂<superscript>2-</superscript> are discussed, as well as the limitations of this work and the associated perspectives.<br /> (© 2026. The Author(s), under exclusive licence to Japanese Society of Radiological Technology and Japan Society of Medical Physics.)
– Name: Abstract
  Label: Competing Interests
  Group: Ab
  Data: Declarations. Conflicts of interest: The authors declare that they have no conflict of interest. Ethics approval: This study is based on numerical simulations and computational modeling of X-ray–induced air ionization under clinical radiological conditions. No human subjects, biological samples, or direct clinical interventions were involved. Therefore, ethical approval was not required. Informed consent: This study did not involve human participants or patient-specific clinical data. Therefore, informed consent was not required.
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  Label: References
  Group: RefInfo
  Data: Research (Wash D C). 2021 Dec 26;2021:9892152. (PMID: <searchLink fieldCode="PM" term="%2235028585%22">35028585)</searchLink><br />Commun Chem. 2021 Apr 8;4(1):49. (PMID: <searchLink fieldCode="PM" term="%2236697542%22">36697542)</searchLink><br />Front Public Health. 2020 Dec 15;8:601711. (PMID: <searchLink fieldCode="PM" term="%2233384980%22">33384980)</searchLink><br />Cureus. 2024 Dec 3;16(12):e75054. (PMID: <searchLink fieldCode="PM" term="%2239749071%22">39749071)</searchLink><br />Indian J Radiol Imaging. 2025 Aug 12;36(3):334-344. (PMID: <searchLink fieldCode="PM" term="%2242344198%22">42344198)</searchLink><br />Proc Jpn Acad Ser B Phys Biol Sci. 2017;93(6):399-421. (PMID: <searchLink fieldCode="PM" term="%2228603211%22">28603211)</searchLink>
– Name: SubjectMinor
  Label: Contributed Indexing
  Group:
  Data: <i>Keywords: </i>Air ionization; Backscatter flux; HCNO phantom; Monte Carlo simulation; Radiation transport
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  Data: <i>Date Created: </i>20260713 <i>Date Completed: </i>20260905 <i>Latest Revision: </i>20261008
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  Data: 20261008
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  Data: 10.1007/s12194-026-01094-2
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