arXiv subjects

Eugene Surdutovich

Publications and source records attributed to Eugene Surdutovich.

16 recordsLinked to original sources

arXiv2021

Theoretical ground for precursors-based molecular spectroscopy

A theory for excitation of molecular resonances by a train of precursors is developed. Right at the vacuum-medium interface, a train of incident square waves interacts with light electrons and is converted into a train of precursors, which further excite molecular dipoles. Analytic calculations indicate that these excited dipoles generate radiation, including secondary precursors propagating in the backward direction. Encoded in this radiation are proper frequencies of excited molecular dipoles allowing for spectroscopic measurements. The frequency of the train of incident square pulses can be by several orders of magnitude smaller than the proper frequencies of molecular resonances.

physics.optics↗

arXiv2018

Phenomenon-based prediction of relative biological effectiveness of ion beams by means of the MultiScale Approach

Relative biological effectiveness (RBE) is a key quantity for the description of radiobiological effects induced by charged-particle irradiation in the context of ion-beam cancer therapy. Since RBE is a complex function that depends on different physical, chemical and biological parameters, a fundamental understanding of these effects becomes increasingly important for clinical applications. The phenomenon-based MultiScale Approach to the physics of radiation damage with ions (MSA) provides a tool for a molecular-level understanding of physical and chemical mechanisms of radiation biodamage and allows to quantify macroscopic biological effects caused by ion irradiation. This study reports the first application of the MSA for the analysis of RBE of ion beams. As a case study, we quantify the response of human normal tissue cell lines to carbon-ion irradiation at different values of linear energy transfer. RBE corresponding to different biological endpoints as well as other radiobiological parameters, such as clonogenic cell survival as a function of dose and inactivation cross section, are analyzed and compared with experimental data. Good agreement with an extensive data set emphasizes the predictive power of the MSA. The method is also used to make predictions of RBE at high values of LET where RBE decreases due to the "overkill" effect. In this regime, the dose needed to achieve a given biological effect is deposited by a few ions. The fact that a given number of ions may produce more damage than needed for a given effect leads to a significant (up to 20%) variation in RBE. This effect should be taken into consideration in the analysis of experimental data on irradiation with high-LET ions.

physics.med-ph↗

arXiv2018

Transport of secondary electrons through coatings of ion-irradiated metallic nanoparticles

The transport of low-energy electrons through the coating of a radiosensitizing metallic nanoparticle under fast ion irradiation is analyzed theoretically and numerically. As a case study, we consider a poly(ethylene glycol)-coated gold nanoparticle of diameter 1.6~nm excited by a carbon ion in the Bragg peak region in water as well as by more energetic carbon ions. The diffusion equation for low-energy electrons emitted from a finite-size spherical source representing the surface of the metal core is solved to obtain the electron number density as a function of radial distance and time. Information on the atomistic structure and composition of the coating is obtained from molecular dynamics simulations performed with the MBN Explorer software package. Two mechanisms of low-energy electron production by the metallic core are considered: the relaxation of plasmon excitations and collective excitations of valence $d$ electrons in individual atoms of gold. Diffusion coefficients and characteristic lifetimes of electrons propagating in gold, water, and poly(ethylene glycol) are obtained from relativistic partial wave analysis and the dielectric formalism, respectively. On this basis, the number of electrons released through the organic coating into the surrounding aqueous medium and the number of hydroxyl radicals produced are evaluated. The largest increase of the radical yield due to low-energy electrons is observed when the nanoparticle is excited by an ion with energy significantly exceeding that in the Bragg peak region. It is also shown that the water content of the coating, especially near the surface of the metal core, is crucial for the production of hydroxyl radicals.

physics.atm-clus↗

arXiv2018

Calculation of survival probabilities for cells exposed to high ion fluences

A methodology of calculations of survival curves with an account for ion paths interference is developed using the multiscale approach to the physics of radiation damage with ions. The method is applied to different targets and shouldered survival curves are obtained. The recipe is designed for both high and low values of linear energy transfer.

physics.med-ph↗

arXiv2017

The effect of ion-induced shock waves on the transport of reacting species around energetic ion tracks

The passage of energetic ions through tissue initiates a series of physico-chemical events, which lead to biodamage. The study of this scenario using a multiscale approach brought about the theoretical prediction of shock waves initiated by energy deposited within ion tracks. These waves are being explored in this letter in different aspects. The radial dose that sets their initial conditions is calculated using diffusion equations extended to include the effect of energetic $δ$-electrons. The resulting shock waves are simulated by means of reactive classical molecular dynamics. The simulations predict a characteristic distribution of reactive species which may have a significant contribution to biodamage, and also suggests experimental means to detect the shock waves.

physics.bio-ph↗

arXiv2017

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

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 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 molecular dynamics simulations.

physics.bio-ph↗

arXiv2017

Cell survival probability in a spread-out Bragg peak for novel treatment planning

The problem of variable cell survival probability along the spread-out Bragg peak is one of the long standing problems in planning and optimisation of ion-beam therapy. This problem is considered using the multiscale approach to the physics of ion-beam therapy. The physical reasons for this problem are analysed and understood on a quantitative level. A recipe of solution to this problem is suggested using this approach. This recipe can be used in the design of a novel treatment planning and optimisation based on fundamental science.

physics.med-ph↗

arXiv2017

Ion-impact-induced multifragmentation of liquid droplets

An instability of a liquid droplet traversed by an energetic ion is explored. This instability is brought about by the predicted shock wave induced by the ion. An observation of multifragmentation of small droplets traversed by ions with high linear energy transfer is suggested to demonstrate the existence of shock waves. A number of effects are analysed in effort to find the conditions for such an experiment to be signifying. The presence of shock waves crucially affects the scenario of radiation damage with ions since the shock waves significantly contribute to the thermomechanical damage of biomolecules as well as the transport of reactive species. While the scenario has been upheld by analyses of biological experiments, the shock waves have not yet been observed directly, regardless of a number of ideas of experiments to detect them were exchanged at conferences.

physics.med-ph↗

arXiv2015

Transport of secondary electrons and reactive species in ion tracks

The transport of reactive species brought about by ions traversing tissue-like medium is analysed analytically. Secondary electrons ejected by ions are capable of ionizing other molecules; the transport of these generations of electrons is studied using the random walk approximation until these electrons remain ballistic. Then, the distribution of solvated electrons produced as a result of interaction of low-energy electrons with water molecules is obtained. The radial distribution of energy loss by ions and secondary electrons to the medium yields the initial radial dose distribution, which can be used as initial conditions for the predicted shock waves. The formation, diffusion, and chemical evolution of hydroxyl radicals in liquid water are studied as well.

physics.bio-ph↗

arXiv2015

Comparative analysis of the secondary electron yield from carbon nanoparticles and pure water medium

The production of secondary electrons generated by carbon nanoparticles and pure water medium irradiated by fast protons is studied by means of model approaches and Monte Carlo simulations. It is demonstrated that due to a prominent collective response to an external field, the nanoparticles embedded in the medium enhance the yield of low-energy electrons. The maximal enhancement is observed for electrons in the energy range where plasmons, which are excited in the nanoparticles, play the dominant role. Electron yield from a solid carbon nanoparticle composed of fullerite, a crystalline form of C60 fullerene, is demonstrated to be several times higher than that from liquid water. Decay of plasmon excitations in carbon-based nanosystems thus represents a mechanism of increase of the low-energy electron yield, similar to the case of sensitizing metal nanoparticles. This observation gives a hint for investigation of novel types of sensitizers to be composed of metallic and organic parts.

physics.atm-clus↗

arXiv2013

Multiscale approach to the physics of radiation damage with ions

The multiscale approach to the assessment of biodamage resulting upon irradiation of biological media with ions is reviewed, explained and compared to other approaches. The processes of ion propagation in the medium concurrent with ionization and excitation of molecules, transport of secondary products, dynamics of the medium, and biological damage take place on a number of different temporal, spatial and energy scales. The multiscale approach, a physical phenomenon-based analysis of the scenario that leads to radiation damage, has been designed to consider all relevant effects on a variety of scales and develop an approach to the quantitative assessment of biological damage as a result of irradiation with ions. This paper explains the scenario of radiation damage with ions, overviews its major parts, and applies the multiscale approach to different experimental conditions. On the basis of this experience, the recipe for application of the multiscale approach is formulated. The recipe leads to the calculation of relative biological effectiveness.

physics.bio-ph↗

arXiv2012

Calculation of complex DNA damage induced by ions

This paper is devoted to the analysis of the complex damage of DNA irradiated by ions. The analysis and assessment of complex damage is important because cells in which it occurs are less likely to survive because the DNA repair mechanisms may not be sufficiently effective. We studied the flux of secondary electrons through the surface of nucleosomes and calculated the radial dose and the distribution of clustered damage around the ion's track. The calculated radial dose distribution is compared to simulations. The radial distribution of the complex damage is found to be different from that of the dose. Comparison with experiments may solve the question of what is more lethal for the cell, damage complexity or absorbed energy. We suggest a way to calculate the probability of cell death based on the complexity of the damage. This work is done within the framework of the phenomenon-based multiscale approach to radiation damage by ions.

physics.bio-ph↗

arXiv2012

Double strand breaks in DNA resulting from double-electron-emission events

A mechanism of double strand breaking (DSB) in DNA due to the action of two electrons is considered. These are the electrons produced in the vicinity of DNA molecules due to ionization of water molecules with a consecutive emission of two electrons, making such a mechanism possible. This effect qualitatively solves a puzzle of large yields of DSBs following irradiation of DNA molecules. The transport of secondary electrons, including the additional electrons, is studied in relation to the assessment of radiation damage due to incident ions. This work is a stage in the inclusion of Auger mechanism and like effects into the multiscale approach to ion-beam cancer therapy.

physics.bio-ph↗

arXiv2009

Spectra of secondary electrons generated in water by energetic ions

The energy distributions of secondary electrons produced by energetic carbon ions (in the energy range used, e.g., in hadron therapy), incident on liquid water, are discussed. For low-energy ions, a new parameterization of the singly-differential ionization cross sections is introduced, based on tuning the position of the Bragg peak. The resulting parameterization allows a fast calculation of the energy spectra of secondary electrons at different depths along the ion's trajectory, especially near the Bragg peak. At the same time, this parameterization provides penetration depths for a broad range of initial-ion energies within the therapeutically-accepted error. For high-energy ions, the energy distribution is obtained with a use of the dielectric response function approach. Different models are compared and discussed.

physics.bio-ph↗

arXiv2008

Physics of ion beam cancer therapy: a multi-scale approach

We propose a multi-scale approach to understand the physics related to ion-beam cancer therapy. It allows the calculation of the probability of DNA damage as a result of irradiation of tissues with energetic ions, up to 430 MeV/u. This approach covers different scales, starting from the large scale, defined by the ion stopping, followed by a smaller scale, defined by secondary electrons and radicals, and ending with the shortest scale, defined by interactions of secondaries with the DNA. We present calculations of the probabilities of single and double strand breaks of DNA, suggest a way to further expand such calculations, and also make some estimates for glial cells exposed to radiation.

physics.bio-ph↗

arXiv2008

Ion-beam therapy: from electron production in tissue like media to DNA damage estimations

Radiation damage induced by ion beams is traditionally treated at different levels of theoretical approaches, for the different scales and mechanisms involved.We present here details of a combined approach that, from a method at a nanoscopic scale, attempts to merge with higher scales existing results, by tuning the analytical method employed when extended to larger scale and so yielding a consistent picture of the entire process. Results will show the possibility to get a good agreement with macroscale methods and, on the other hand, to produce a reliable electron energy spectra to be used for DNA damage estimations.

physics.bio-ph↗