Single track nanodosimetry of low energy electrons

Bantsar, A.; Großwendt, B.; Pszona, S.; Kula, J.

doi:10.1016/j.nima.2008.11.021

Cited by 14 publications

(10 citation statements)

References 11 publications

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“…As far as the relation between radiation physics and radiobiology is concerned, the cluster-size formation in the track-core and the penumbra region should also be measured using target volumes comparable in size with nucleosomes and, in particular, with short segments of the DNA that are assumed today to be the most important radiation-sensitive biological target volumes with respect to radiation-induced damage to genes and cells. The relation of radiobiological data and parameters derived from ionization cluster-size distributions is extensively illustrated and discussed in several papers (see, for instance, Grosswendt 2004, 2005, 2007, Schulte et al 2008, Bantsar et al 2009. In particular, Garty et al and Schulte et al described and applied a complete nanodosimetric model of radiation-induced DNA damage, based on a combinatorial approach to translate ionizations caused by ionizing particles in gas volumes to lesions in short DNA segments.…”

Section: Discussionmentioning

confidence: 99%

Track structure of light ions: experiments and simulations

et al. 2012

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To study the track structure of light ions, a measuring device has been developed at the Legnaro National Laboratory of INFN, which can be used to investigate separately the penumbra region of particle tracks and the trackcore region, which is a few nanometres in diameter. The device is based on single-electron counting techniques by means of a gas detector; it simulates a 'nanometre-sized' biological volume of about 20 nm in diameter that can be moved with respect to a narrow particle beam to measure the ionizationcluster-size distributions caused within the target volume by the passage of single primary particles, as a function of the impact parameter. To investigate the ionization-cluster-size formation caused by primary particles of medical interest when they penetrate through or pass by the target volume at a specified impact parameter, measurements and Monte Carlo simulations were performed for 20 MeV protons, 16 MeV deuterons, 48 MeV 6 Li-ions, 26.7 MeV 7 Li-ions and 96 MeV 12 C-ions. The detailed analysis of the resulting distributions showed that in the track-core region their shape is mainly determined by the mean free ionization path length of the primary particles, whereas in the penumbra region the shape of the distributions is almost independent of the impact parameter, and also of the particle type and velocity.

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Section: Discussionmentioning

confidence: 99%

Track structure of light ions: experiments and simulations

et al. 2012

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“…The probabilities in ( Eq 5 ) are squared, as in our geometry two independent DSBs are needed, one on tetranucleosome A and one on tetranucleosome B. The probabilities F 2 and p 1 were taken from nanodosimetric experiments with electrons of various energies from Bantsar [ 25 – 27 ]. In Fig 5 ε ion is plotted as a function of electron energy as the solid line.…”

Section: Methodsmentioning

confidence: 99%

The Impact of the Geometrical Structure of the DNA on Parameters of the Track-Event Theory for Radiation Induced Cell Kill

2016

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Background and PurposeWhen fractionation schemes for hypofractionation and stereotactic body radiotherapy are considered, a reliable cell survival model at high dose is needed for calculating doses of similar biological effectiveness. An alternative to the LQ-model is the track-event theory which is based on the probabilities for one- and two two-track events. A one-track-event (OTE) is always represented by at least two simultaneous double strand breaks. A two-track-event (TTE) results in one double strand break. Therefore at least two two-track-events on the same or different chromosomes are necessary to produce an event which leads to cell sterilization. It is obvious that the probabilities of OTEs and TTEs must somehow depend on the geometrical structure of the chromatin. In terms of the track-event theory the ratio ε of the probabilities of OTEs and TTEs includes the geometrical dependence and is obtained in this work by simple Monte Carlo simulations.Materials and MethodsFor this work it was assumed that the anchors of loop forming chromatin are most sensitive to radiation induced cell deaths. Therefore two adjacent tetranucleosomes representing the loop anchors were digitized. The probability ratio ε of OTEs and TTEs was factorized into a radiation quality dependent part and a geometrical part: ε = εion ∙ εgeo. εgeo was obtained for two situations, by applying Monte Carlo simulation for DNA on the tetranucleosomes itself and for linker DNA. Low energy electrons were represented by randomly distributed ionizations and high energy electrons by ionizations which were simulated on rays. εion was determined for electrons by using results from nanodosimetric measurements. The calculated ε was compared to the ε obtained from fits of the track event model to 42 sets of experimental human cell survival data.ResultsWhen the two tetranucleosomes are in direct contact and the hits are randomly distributed εgeo and ε are 0.12 and 0.85, respectively. When the hits are simulated on rays εgeo and ε are 0.10 and 0.71. For the linker-DNA εgeo and ε for randomly distributed hits are 0.010 and 0.073, and for hits on rays 0.0058 and 0.041, respectively. The calculated ε fits the experimentally obtained ε = 0.64±0.32 best for hits on the tetranucleosome when they are close to each other both, for high and low energy electrons.ConclusionsThe parameter εgeo of the track event model was obtained by pure geometrical considerations of the chromatin structure and is 0.095 ± 0.022. It can be used as a fixed parameter in the track-event theory.

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“…Simulated ICSDs were also compared with those obtained experimentally in order to benchmark the cross section data implemented in both Geant4-DNA and PTra codes. Measured ICSDs for low-energy monoenergetic electron beams traversing a "nanometric" nitrogen target are reported by Bancer et al [27,34]. The study includes a detailed description of the Jet Counter nanodosimeter and experimental setup used to carry out the measurements.…”

Section: Comparison With Experimental Datamentioning

confidence: 99%

“…Figure 7 shows a comparison of the measured [27] and simulated ICSDs in nitrogen. In the interest of readability, only the simulation results obtained with Geant4-DNA are shown.…”

Section: Experimental Validationmentioning

confidence: 99%

“…For energies less than 10 keV, the comparison was made against a model presented by Gümüş [26]. In this low energy range, simulated ICSDs were also compared to those obtained experimentally (in nitrogen) by Bancer (aka Bantsar) et al using the Jet Counter nanodosimeter at NCBJ [27]. The good agreement between Geant4-DNA and PTra codes for simulated quantities such as ICSDs as well as experimental results and published data on stopping power and range values satisfies the requirement for their release in the Geant4 code.…”

Section: Introductionmentioning

confidence: 99%

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