Low Energy Particle Track Simulation Research Articles

Modeling secondary particle tracks generated by intermediate- and low-energy protons in water with the Low-Energy Particle Track Simulation code

Using a recent extension of the Low-Energy Particle Track Simulation (LEPTS) Monte Carlo code, we model the slowing-down of heavy charged particles propagating in water, combined with an explicit molecular-level description of radiation effects due to the formation of secondary electrons, their propagation through the medium, and electron-induced molecular dissociations. As a case study, we consider the transport of protons with the initial energy of 1MeV until their thermalization, so that we cover the energy range that contributes mainly to the energy deposition in the Bragg peak region. In order to include protons into the simulation procedure, a comprehensive dataset of integral and differential cross sections of elastic and inelastic scattering of intermediate- and low-energy protons from water molecules is created. Experimental and theoretical cross sections available in the literature are carefully examined, compared and verified. The ionization cross section by protons includes recent experimental measurements of the production of different charged fragments.

Induced molecular dissociations as a radiation damage descriptor (Nanodosimetry)

SynopsisWe present a nanodosimeter software based on Monte Carlo, termed: Low Energy Particle Track Simulation. For medical applications purposes, we propose bond breakings to describe the energy deposited taking water as an example. This tool aims to improve current treatment planning approach based on absorbed dose.

Integration of the low-energy particle track simulation code in Geant4

The Low-Energy Particle Track Simulation code (LEPTS) is a Monte Carlo code developed to simulate the damage caused by radiation at molecular level. The code is based on experimental data of scattering cross sections, both differential and integral, and energy loss data, complemented with theoretical calculations. It covers the interactions of electrons and positrons from energies of 10 keV down to 0.1 eV in different biologically relevant materials. In this article we briefly mention the main characteristics of this code and we present its integration within the Geant4 Monte Carlo toolkit.

Modeling secondary particle tracks generated by high-energy protons in water

SynopsisWe present interaction probability data of low-energy secondary electrons and positrons produced due to the proton impact. The probability distribution functions serve as input data for the Low Energy Particle Track Simulation (LEPTS) approach which allows one to include the effect of low-energy species in medical applications of radiation and in ion-beam cancer therapy, in particular.

Differential and integral electron scattering cross sections from tetrahydrofuran (THF) over a wide energy range: 1–10 000 eV

Total, integral inelastic and integral and differential elastic cross sections have been calculated with the screening-corrected additivity rule (SCAR) method based on the independent atom model (IAM) for electron scattering from tetrahydrofuran (THF). Since the permanent dipole moment of THF enhances rotational excitation particularly at low energies and for small angles, an estimate of the rotational excitation cross section was also computed by assuming the interaction with a free electric dipole as an independent, additional process. Our theoretical results compare very favourably to the existing experimental data. Finally, a self-consistent set of integral and differential interaction CSs for the incident energy range 1 eV–10 keV is established for use in our low energy particle track simulation (LEPTS). All cross section data are supplied numerically in tabulated form.

Clustering and condensation effects in the electron scattering cross sections from water molecules

Clustering effects in the differential and integral electron scattering cross sections have been investigated by calculating their magnitudes for different water cluster configurations: specifically for the dimer, trimer and tetramer. By assuming that condensation effects can be described in terms of modifications to the single molecule electron scattering cross sections, induced by the surrounding molecules, effective data for liquid water is also provided. Comparison with previous calculations in liquid water has been carried out through the inelastic mean free path, i.e. the mean length between successive inelastic collisions. Although a satisfactory agreement for high energies, above 100eV, has been found, for lower energies some discrepancies remain and so will be the subject of further investigation. As an example of modelling electron interactions in soft matter, the present set of data has been employed to simulate single electron tracks in liquid water. This was achieved using our Low Energy Particle Track Simulation (LEPTS) code.

Modelling low energy electron and positron tracks in biologically relevant media

This colloquium describes an approach to incorporate into radiation damage models the effect of low and intermediate energy (0–100 eV) electrons and positrons, slowing down in biologically relevant materials (water and representative biomolecules). The core of the modelling procedure is a C++ computing programme named “Low Energy Particle Track Simulation (LEPTS)”, which is compatible with available general purpose Monte Carlo packages. Input parameters are carefully selected from theoretical and experimental cross section data and energy loss distribution functions. Data sources used for this purpose are reviewed showing examples of electron and positron cross section and energy loss data for interactions with different media of increasing complexity: atoms, molecules, clusters and condense matter. Finally, we show how such a model can be used to develop an effective dosimetric tool at the molecular level (i.e. nanodosimetry). Recent experimental developments to study the fragmentation induced in biologically material by charge transfer from neutrals and negative ions are also included.

Current prospects on Low Energy Particle Track Simulation for biomedical applications

The Low Energy Particle Track Simulation code is a radiation interaction simulation tool specifically designed to describe electron and positron interactions below 10keV at a molecular level. Relying on carefully selected, preferentially experimental input parameters that account for all expected scattering processes, it provides detailed results about all collisional events undergone by an incident radiation particle during its slowdown until thermalisation. Here, we give an up-to-date description of its input data sources and selection procedure and summarise the current contents of the resulting database.

Interaction model for electron scattering from ethylene in the energy range 1–10 000 eV

We present new experimental electron energy loss distribution functions for ethylene (C2H4) measured with two different apparatus (Liège and Madrid) in different incident electron energy ranges. Theoretical cross sections for electron scattering from C2H4 were calculated using the screening-corrected additivity rule (IAM-SCAR) method. Through a critical comparison of our new data and existing results from other groups, we obtain a self-consistent set of recommended interaction cross section values and energy loss spectra. Finally, electron tracks in C2H4 are simulated with our Low Energy Particle Track Simulation (LEPTS) in order to demonstrate the efficacy of our recommended data.

Modelling low energy electron and positron tracks for biomedical applications

In order to incorporate the effect of low energy electrons and positron in radiation damage models, the simulation method proposed here is based on experimental and theoretical cross section data and energy loss spectra we have previously derived. After a summary of the main techniques used to obtain reliable input data, the basis of a Low Energy Particle Track Simulation (LEPTS) procedure is established. Single electron and positron tracks in liquid water are presented and the possibility of using these results to develop tools for nanodosimetry is discussed.

Modelling low energy electron and positron tracks for biomedical applications

Purpose: To incorporate the effects of low energy electrons and positrons into radiation interaction models.Materials and methods: The simulation method proposed here was based on experimental and theoretical cross section data and energy loss spectra we have previously derived. After a summary of the main techniques used to obtain reliable input data, the basis of a Low Energy Particle Track Simulation (LEPTS) procedure was established. The programme is specifically designed to describe electron and positron interactions below 10 keV, down to thermal energies.Results: Single electron and positron tracks in water are presented and the possibility of using these results to develop tools for nanodosimetry is discussed.Conclusions: Standard approximations based on high incident energies, such as the Born-Bethe theory, are not suitable to simulate electron and positron tracks below 10 keV. Prior to the inclusion of low-energy effects in a radiation model, an appropriate study is required to determine both the interaction cross sections and the energy loss spectra.

Energy deposition by a 106Ru/106Rh eye applicator simulated using LEPTS, a low-energy particle track simulation

The present study introduces LEPTS, an event-by-event Monte Carlo programme, for simulating an ophthalmic (106)Ru/(106)Rh applicator relevant in brachytherapy of ocular tumours. The distinctive characteristics of this code are the underlying radiation-matter interaction models that distinguish elastic and several kinds of inelastic collisions, as well as the use of mostly experimental input data. Special emphasis is placed on the treatment of low-energy electrons for generally being responsible for the deposition of a large portion of the total energy imparted to matter.