39 research outputs found
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.Comment: 31 pages, 14 figure
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.Comment: 7 pages 4 figure
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.Comment: 9 pages, 6 figures, submitted to Eur. Phys. J.
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.Comment: 6 pages, 3 figures, submitted to EPJ
Biodamage via shock waves initiated by irradiation with ions
Radiation damage following the ionising radiation of tissue has different scenarios and mechanisms depending on the projectiles or radiation modality. We investigate the radiation damage effects due to shock waves produced by ions. We analyse the strength of the shock wave capable of directly producing DNA strand breaks and, depending on the ion's linear energy transfer, estimate the radius from the ion's path, within which DNA damage by the shock wave mechanism is dominant. At much smaller values of linear energy transfer, the shock waves turn out to be instrumental in propagating reactive species formed close to the ion's path to large distances, successfully competing with diffusion
Electric dipole moments of nitric acid-water complexes measured by cluster beam deflection
Water clusters embedding a nitric acid molecule HNO3(H2O)_{n=1-10} are
investigated via electrostatic deflection of a molecular beam. We observe large
paraelectric susceptibilities that greatly exceed the electronic
polarizability, revealing the contribution of permanent dipole moments. The
moments derived from the data are also significantly higher than those of pure
water clusters. An enhancement in the susceptibility for n=5,6 and a rise in
cluster abundances setting in at n=6 suggest that dissociation of the solvated
acid molecule into ions takes place in this size range.Comment: Proceedings of ISACC 2009, The Fourth International Symposium "Atomic
Cluster Collisions: structure and dynamics from the nuclear to the biological
scale" (AIP Conference Proceedings
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.Comment: 18 pag,5 fig, submitted to PR