Secondary electron fluence generated in LiF:Mg,Ti by low-energy photons and its contribution to the absorbed dose

Cabrera-Santiago, A; Massillon‐JL, G.

doi:10.1063/1.4954091

“…Thus, to evaluate the impact of the electron range on the absorbed dose, the CSDA range for electrons with energy between 1 keV and 10 keV in LiF has been assessed 11 using experimental data published by Morbitzer and Scharmann 16 . With the obtained results, the irradiated mass was estimated and a better agreement on RE of 0.7%-8% was observed despite of the uncertainties 11 . It was concluded that the absorbed dose delivered by low photon energy is not accurately known 11 On the other hand, outside of radiotherapy fields where low photon energy spectra exist 16,17 discrepancies are commonly observed on the absorbed dose measured with different dosimeters [18][19][20] .…”

mentioning

confidence: 53%

“…With the obtained results, the irradiated mass was estimated and a better agreement on RE of 0.7%-8% was observed despite of the uncertainties 11 . It was concluded that the absorbed dose delivered by low photon energy is not accurately known 11 On the other hand, outside of radiotherapy fields where low photon energy spectra exist 16,17 discrepancies are commonly observed on the absorbed dose measured with different dosimeters [18][19][20] . This can be associated to two possible phenomena: a lack of information about the electron interaction at low energy and/or the limited understanding about the relationship between the absorbed dose and the dosimeter's response.…”

mentioning

confidence: 53%

“…In addition, low-energy secondary electrons (SE), have been shown to be the main participants in the processes of ionization and responsible for radiation damage in matter 8 . Therefore, knowledge of the electron spectra [9][10] and their corresponding CSDA range 11 are essential to accurately determine the absorbed dose and evaluate the radiation effect in matter. For accurate low-energy dosimetry, there are two fundamental questions to ask: How many electrons are produced during the interaction?…”

mentioning

confidence: 99%

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Future Directions on Low-Energy Radiation Dosimetry

Massillon‐JL

¹

2021

Preprint

0

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For more than one century, low-energy (< 100 keV) photons (x-rays and gamma) have been widely used in different areas including biomedical research and medical applications such as mammography, fluoroscopy, general radiography, computed tomography, and brachytherapy treatment, amongst others. It has been demonstrated that most of the electrons produced by low photon energy beams have energies below 10 keV. However, the physical processes by which these low energy electrons interact with matter are not yet well understood. Besides, it is generally assumed that all the energy deposited within a dosimeter sensitive volume is transformed into a response. But such an assumption could be incorrect since part of the energy deposited might be used to create defects or damages at the molecular and atomic level. Consequently, the relationship between absorbed dose and dosimeter response can be mistaken. During the last few years, efforts have been made to identify models that allow to understand these interaction processes from a quantum mechanical point of view. Some approaches are based on electron-beam − solid-state-interaction models to calculate electron scattering cross-sections while others consider the density functional theory method to localize low energy electrons and evaluate the energy loss due to the creations of defects and damages in matter. The results obtained so far could be considered as a starting point. This paper presents some methodologies based on fundamental quantum mechanics which can be considered useful for dealing with low-energy interactions.

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“…Φ E E and ( ) are the calculated unrestricted and restricted stopping power 37 , the electron energy and the electron energy fluence, respectively. ∆ ∆ ∆ Φ S( ) ( ) represents all the electrons that fall below ∆ = 1 keV 36 due to the lack of accurate electron cross sections at energies below 1 keV 8,38 .…”

Section: Methodsmentioning

confidence: 99%

Track and dose-average LET dependence of Gafchromic EBT3 and MD-V3 films exposed to low-energy photons

Massillon‐JL

¹

2020

Sci Rep

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Gafchromic films are widely used in radiotherapy using photons, electrons and protons. Dosimetric characteristics of the films in terms of beam-quality is of great importance for a better evaluation of the absorbed-dose in the clinic. In proton-therapy, film's response has been reported in terms of track-average, L Δ,T , or dose-average, L Δ,D , linear energy transfer (LET), concluding that L Δ,D is a more reliable parameter than L Δ,T. Nonetheless, in photon-beams, the film's response is generally scrutinised in terms of photon-energy. This work aimed at investigating, the total (TEF) and secondary (SE) electron fluence produced in EBT3 and MD-V3 films exposed to 20 kV-160 kV x-ray and 60 Co beams and their corresponding L Δ,T and L Δ,D to determine their influence on the film's relative-efficiency, RE Film. Regardless the film-model, at energies below 100 keV, L Δ,D for TEF are about 1.7 to 2.5 times those of L Δ,T while for SE they are relatively similar (8-29%). For 60 Co-gamma, L Δ,D for tef and Se are approximately 9 and 4 times L Δ,T , respectively, which implies that L Δ,D is more important for highphoton energies. Independent of the electron-fluence and film-model, RE Film is almost constant at low average-LET, rapidly increases and thereafter steadily rises with average-LET. The RE Film −LET curve indicated that L Δ,D is more sensitive to small change than L Δ,T and if it is evaluated for SE, it would even be more appropriate to better describing the dosimeter response induced by photons in terms of ionization-density instead of L Δ,T for TEF, as generally done. Based on these results, once can conclude that the effect of the average-LET on the film's response should be considered when use for clinicaldosimetry using photons and not only the energy. After the introduction of the linear energy transfer (LET) concept by Zirkle and colleagues 1 , the international commission on radiation units and measurement (ICRU) 2 has adopted two non-stochastic quantities to describe the quality of an ionising radiation beam: the track-average LET, L Δ,T , which describes the average energy lost by charged particles due to collisions per distance travelled with energy transfers less than some specific Δ value and the dose-average LET, L Δ,D , that corresponds to the average LET associated to the absorbed dose distribution 2. Since then, L Δ,T has been conventionally used to quantify the radiation-induced effect in any biological 3-6 and physical 7-12 systems. During the last few years, the dose-average LET, L Δ,D has received some particular importance due to the extensive use of protons for radiotherapy treatment where there is an interest for including, into the treatment planning system, parameters that are clinically and biologically relevant 13-15. In terms of macroscopic dosimetric parameters, Paganetti and colleagues have reported that L Δ,D is more suitable for studying the biological effectiveness instead of L Δ,T 13,15 while Guan and collaborators suggested the use of both quantities, but at different energy ...

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“…In addition, low-energy secondary electrons (SE), have been shown to be the main participants in the processes of ionization and responsible for radiation damage in matter 10 . Therefore, knowledge of the electron spectra 11 , 12 and their corresponding CSDA range 13 are essential to accurately determine the absorbed dose and evaluate the radiation effect in matter. For accurate low-energy dosimetry, there are two fundamental questions to ask: How many electrons are produced during the interaction?…”

Section: Introductionmentioning

confidence: 99%

Future directions on low-energy radiation dosimetry

Massillon‐JL

¹

2021

Sci Rep

View full text Add to dashboard Cite

For more than one century, low-energy (< 100 keV) photons (x-rays and gamma) have been widely used in different areas including biomedical research and medical applications such as mammography, fluoroscopy, general radiography, computed tomography, and brachytherapy treatment, amongst others. It has been demonstrated that most of the electrons produced by low photon energy beams have energies below 10 keV. However, the physical processes by which these low energy electrons interact with matter are not yet well understood. Besides, it is generally assumed that all the energy deposited within a dosimeter sensitive volume is transformed into a response. But such an assumption could be incorrect since part of the energy deposited might be used to create defects or damages at the molecular and atomic level. Consequently, the relationship between absorbed dose and dosimeter response can be mistaken. During the last few years, efforts have been made to identify models that allow to understand these interaction processes from a quantum mechanical point of view. Some approaches are based on electron-beam − solid-state-interaction models to calculate electron scattering cross-sections while others consider the density functional theory method to localize low energy electrons and evaluate the energy loss due to the creations of defects and damages in matter. The results obtained so far could be considered as a starting point. This paper presents some methodologies based on fundamental quantum mechanics which can be considered useful for dealing with low-energy interactions.

show abstract

Secondary electron fluence generated in LiF:Mg,Ti by low-energy photons and its contribution to the absorbed dose

Cited by 8 publications

References 7 publications

Future Directions on Low-Energy Radiation Dosimetry

Future Directions on Low-Energy Radiation Dosimetry

Track and dose-average LET dependence of Gafchromic EBT3 and MD-V3 films exposed to low-energy photons

Future directions on low-energy radiation dosimetry

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