Inelastic Collisions of Energetic Protons in Biological Media

Abril, Isabel; García-Molina, Rafael; Vera, Pablo de; Kyriakou, Ioanna; Emfietzoglou, Dimitris

doi:10.1016/b978-0-12-396455-7.00006-6

Cited by 27 publications

(30 citation statements)

References 71 publications

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“…The quantity ω has to take different values in each case in order to integrate to the known stopping power [24]: this is 19 eV for 1-MeV protons, 15 eV for 200-keV/u carbon, and 20.5 eV for 2-MeV/u carbon. The corresponding stopping powers (obtained for ions in liquid water from the dielectric formalism [24][25][26][27]) and ω-values for each case are summarised in Table 1. It is worth noting that for carbon ions in the Bragg peak, ω = 15 eV, as expected.…”

Section: The Contribution Of Sub-45-ev Electrons To the Radial Dose Dmentioning

confidence: 99%

Radial doses around energetic ion tracks and the onset of shock waves on the nanoscale

et al. 2017

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Abstract. Energetic ions lose their energy in tissue mainly by ionising its molecules. This produces secondary electrons which transport this energy radially away from the ion path. The ranges of most of these electrons do not exceed a few nanometres, therefore large energy densities (radial doses) are produced within a narrow region around the ion trajectory. Large energy density gradients correspond to large pressure gradients and this brings about shock waves propagating away from the ion path. Previous works have studied these waves by molecular dynamics (MD) simulations investigating their damaging effects on DNA molecules. However, these simulations where performed assuming that all energy lost by ions is deposited uniformly in thin cylinders around their path. In the present work, the radial dose distributions, calculated by solving the diffusion equation for the low energy electrons and complemented with a semi-empirical inclusion of more energetic δ-electrons, are used to set up initial conditions for the shock wave simulation. The effect of these energy distributions vs. stepwise energy distributions in tracks on the strength of shock waves induced by carbon ions both in the Bragg peak region and out of it is studied by MD simulations.

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Section: The Contribution Of Sub-45-ev Electrons To the Radial Dose Dmentioning

confidence: 99%

Radial doses around energetic ion tracks and the onset of shock waves on the nanoscale

et al. 2017

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“…The doubly differential inverse mean free path (DDiMFP) [29] for inelastic interactions with energy transferhω and momentum transfer hk is given by [30]:…”

Section: A Proton Projectilesmentioning

confidence: 99%

Energy deposition around swift proton tracks in polymethylmethacrylate: How much and how far

et al. 2017

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The use of proton beams in several modern technologies to probe or modify the properties of materials, such as proton beam lithography or ion beam cancer therapy, requires us to accurately know the extent to which the energy lost by the swift projectiles in the medium is redistributed radially around their tracks, since this determines several endpoints, such as the resolution of imaging or manufacturing techniques, or even the biological outcomes of radiotherapy. In this paper, the radial distribution of the energy deposited around swift-proton tracks in polymethylmethacrylate (PMMA) by the transport of secondary electrons is obtained by means of a detailed Monte Carlo simulation. The initial energy and angular distributions of the secondary electrons generated by proton impact, as well as the electronic cross sections for the ejection of these electrons, are reliably calculated in the framework of the dielectric formalism, where a realistic electronic excitation spectrum of PMMA is accounted for. The cascade of all secondary electrons generated in PMMA is simulated taking into account the main interactions that occur between these electrons and the condensed phase target. After analyzing the influence that several angular distributions of the electrons generated by the proton beam have on the resulting radial profiles of deposited energy, we conclude that the widely used Rudd and Kim formula should be replaced by the simpler isotropic angular distribution, which leads to radial energy distributions comparable to the ones obtained from more realistic angular distributions. By studying the dependence of the radial dose on the proton energy we recommend lower proton energies than previously published for reducing proximity effects around a proton track. The obtained results are of relevance for assessing the resolution limits of proton beam based imaging and manufacturing techniques.

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“…When fast projectile (proton) moves in substance material such as (liquid water, DNA and another compound) with mass M1, atomic mass Z1, kinetic energy T, and charge, it induces electronic excitations and ionizations in the material, losing energy in the process [12]. The probability per unite path length that a projectile with charge state q and energy T produces in the target an excitation of energy E=ħw irrespective of its momentum, ħk, (in a.u ħ=1)is given by Sabin and Oddershede [13].…”

Section: Probability Per Unite Lengthmentioning

confidence: 99%

Proton Impact of Bimolecular Targets

Khalaf¹,

Ahmad²,

Al-Ani³

2017

Journal of Asian Scientific Research

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Article HistoryFor a better control and understanding of the effects of radiation damage in living tissues by using the irradiation of biological systems by energetic ion beams have multiple applications in medical physics and space radiation health, such as hadron therapy for cancer treatment and it is necessary to advance an accurate description of the energy loss from the ion beam to the target. In the present work the dielectric formalism like Drude has been used to calculate the probability for an energetic proton and to produce electronic excitations in five targets of high biological interest, namely, liquid water, DNA, PMMA, Adenine and Guanine. Also, the effects of ionization fraction on the mean excitation energy, average energy and Inelastic mean free path studied taking in to consideration electronic excitation in the target. Good agreement achieved with previous work. Contribution/ Originality:This study document an empirical method of obtaining the energy loss function which is the key quantity to study the energy deposited in targets of biological interest by swift projectiles such as protons, so it contains all the information about the electron excitation spectrum of the target.,. The model used through (ELF), namely the extended-Drude ELF. Each term in the sum of Drude-type functions has three adjustable parameters. The parameters a, b and c can be obtained by a fit of Eq. (1) to the ELF for compounds. The energy delivered by a swift proton beam in materials of interest to hadron therapy in 5 compounds is investigated.

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Inelastic Collisions of Energetic Protons in Biological Media

Cited by 27 publications

References 71 publications

Radial doses around energetic ion tracks and the onset of shock waves on the nanoscale

Radial doses around energetic ion tracks and the onset of shock waves on the nanoscale

Energy deposition around swift proton tracks in polymethylmethacrylate: How much and how far

Proton Impact of Bimolecular Targets

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