Limitations (and merits) of PENELOPE as a track-structure code

Fernández-Varea, José M.; González-Muñoz, Gloria; Galassi, M E; Wiklund, Kerstin; Lind, Bengt K.; Ahnesjö, Anders; Tilly, Nina

doi:10.3109/09553002.2011.598209

Cited by 56 publications

(40 citation statements)

References 18 publications

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“…For radiation interactions with GNPs, Geant4-Penelope is unable to precisely reproduce very low-energy electron interactions in the GNP since it is limited to electrons of energies above 100 eV and neglects the reduced dimensionality of the GNPs, this has been shown in work on nanotubes. 31, 43, 44 Furthermore, the interaction probability per Gray with 6 MV photons in this study was found to be higher than that reported in previous studies 9, 18 . We found that this difference was due to the different physics setting used in the two simulations.…”

Section: Discussioncontrasting

confidence: 77%

Dependence of gold nanoparticle radiosensitization on cell geometry

Sung

McNamara

et al. 2017

Nanoscale

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The radiosensitization effect of gold nanoparticles (GNPs) has been demonstrated both in vitro and in vivo in radiation therapy. The purpose of this study was to systematically assess the biological effectiveness of GNPs distributed in the extracellular media for realistic cell geometries. TOPAS-nBio simulations were used to determine the nanometre-scale radial dose distributions around the GNPs, which were subsequently used to predict the radiation dose response of cells surrounded by GNPs. MDA-MB-231 human breast cancer cells and F-98 rat glioma cells were used as models to assess different cell geometries by changing 1) the cell shape, 2) the nucleus location within the cell, 3) the size of GNPs, and 4) the photon energy. The results show that the sensitivity enhancement ratio (SER) was increased up to a factor of 1.2 when the location of the nucleus is close to the cell membrane for elliptical-shaped cells. Heat-maps of damage-likelihoods show that most of the lethal events occur in the regions of the nuclei closest to the membrane, potentially causing highly clustered damage patterns. The effect of the GNP size on radiosensitization was limited when the GNPs were located outside the cell. The improved modelling of the cell geometry was shown to be crucial because the dose enhancement caused by GNPs falls off rapidly with distance from the GNPs. We conclude that radiosensitization can be achieved for kV photons even without cellular uptake of GNPs when the nucleus is shifted towards the cell membrane. Furthermore, damage was found to concentrate in a small region of the nucleus in close proximity to the extracellular, GNP-laden region.

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Section: Discussioncontrasting

confidence: 77%

Dependence of gold nanoparticle radiosensitization on cell geometry

Sung

McNamara

et al. 2017

Nanoscale

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“…The remaining parameters control the mixed simulation algorithm for the transport of electrons and positrons. To force detailed (event-byevent) simulation, the latter parameters were set to zero (21).…”

Section: Monte Carlo Simulations: the Penelope Codementioning

confidence: 99%

Monte Carlo Evaluation of Auger Electron–Emitting Theranostic Radionuclides

et al. 2015

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Several radionuclides used in medical imaging emit Auger electrons, which, depending on the targeting strategy, either may be exploited for therapeutic purposes or may contribute to an unintentional mean absorbed dose burden. In this study, the virtues of 12 Auger electron-emitting radionuclides were evaluated in terms of cellular S values in concentric and eccentric cell-nucleus arrangements and by comparing their dose-point kernels. Methods: The Monte Carlo code PENELOPE was used to transport the full particulate spectrum of 67 Pt, and 201 Tl by means of event-by-event simulations. Cellular S values were calculated for varying cell and nucleus radii, and the effects of cell eccentricity on S values were evaluated. Dosepoint kernels were determined up to 30 μm. Energy deposition at DNA scales was also compared with an α emitter, 223 Ra. Results: PENELOPE-determined S values were generally within 10% of MIRD values when the source and target regions strongly overlapped, that is, S(nucleus←nucleus) configurations, but greater differences were noted for S(nucleus←cytoplasm) and S(nucleus←cell surface) configurations. Cell eccentricity had the greatest effect when the nucleus was small, compared with the cell size, and when the radiation sources were on the cell surface. Dose-point kernels taken together with the energy spectra of the radionuclides can account for some of the differences in energy deposition patterns between the radionuclides. The energy deposition of most Auger electron emitters at DNA scales of 2 nm or less exceeded that of a monoenergetic 5.77-MeV α particle, but not for 223 Ra. Conclusion: A single-cell dosimetric approach is required to evaluate the efficacy of individual radionuclides for theranostic purposes, taking cell geometry into account, with internalizing and noninternalizing targeting strategies. The therapeutic rationale for molecularly targeted radiotherapy is the selective delivery of a radionuclide to tumor cells via a targeting moiety, thereby enhancing the therapeutic index of the agent. Several Auger electron-emitting radionuclides have been proposed for molecularly targeted radiotherapy of small metastases and disseminated cancer cells, with some promising clinical results (1-3). These radionuclides are well suited to serving as molecularly targeted radiotherapy agents because of the extremely short range in matter (nanometers to a few micrometers) of the low-energy, intermediate-linear-energy-transfer (LET) Auger and Coster-Kronig electrons they emit (4). These electrons account for high energy deposition in the immediate vicinity of the decay site, and because of their short range, irradiation of normal neighboring cells is limited, thus reducing nonspecific radiotoxicity. In addition, radiation emitted during the nuclear decay can be exploited for imaging purposes either with SPECT (in the case of g rays in the energy range of 70-360 keV or Bremsstrahlung imaging for pure b 2 emitters) or PET (in the case of annihilation photons), thus making Auger electron-emitting ra...

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“…[3][4][5] A dose enhancement from using GNPs in radiotherapy has already been demonstrated using Monte Carlo simulations; 6 however these simulations are of limited accuracy at micrometer scales, as the continuous physics models used to date break down at small spatial resolutions. 7,8 As one moves towards more accurate microdosimetric measurements of the impact of GNPs, discrete physics models become necessary as they improve the spatial resolution in simulation. As the physical effects of GNP boosted radiotherapy occur across energy scales that descend down to 10 eV, Monte Carlo simulations require discrete physics models down to these very low energies in order to avoid underestimating absorbed dose and secondary particle generation.…”

Section: Introductionmentioning

confidence: 99%

An implementation of discrete electron transport models for gold in the Geant4 simulation toolkit

Sakata

Incerti

Bordage

et al. 2016

Journal of Applied Physics

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Gold nanoparticle (GNP) boosted radiation therapy can enhance the biological effectiveness of radiation treatments by increasing the quantity of direct and indirect radiation-induced cellular damage. As the physical effects of GNP boosted radiotherapy occur across energy scales that descend down to 10 eV, Monte Carlo simulations require discrete physics models down to these very low energies in order to avoid underestimating the absorbed dose and secondary particle generation. Discrete physics models for electron transportation down to 10 eV have been implemented within the Geant4-DNA low energy extension of Geant4. Such models allow the investigation of GNP effects at the nanoscale. At low energies, the new models have better agreement with experimental data on the backscattering coefficient, and they show similar performance for transmission coefficient data as the Livermore and Penelope models already implemented in Geant4. These new models are applicable in simulations focussed towards estimating the relative biological effectiveness of radiation in GNP boosted radiotherapy applications with photon and electron radiation sources. Gold nanoparticle (GNP) boosted radiation therapy can enhance the biological effectiveness of radiation treatments by increasing the quantity of direct and indirect radiation-induced cellular damage. As the physical effects of GNP boosted radiotherapy occur across energy scales that descend down to 10 eV, Monte Carlo simulations require discrete physics models down to these very low energies in order to avoid underestimating the absorbed dose and secondary particle generation. Discrete physics models for electron transportation down to 10 eV have been implemented within the Geant4-DNA low energy extension of Geant4. Such models allow the investigation of GNP effects at the nanoscale. At low energies, the new models have better agreement with experimental data on the backscattering coefficient, and they show similar performance for transmission coefficient data as the Livermore and Penelope models already implemented in Geant4. These new models are applicable in simulations focussed towards estimating the relative biological effectiveness of radiation in GNP boosted radiotherapy applications with photon and electron radiation sources. Published by AIP Publishing. [http://dx

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Limitations (and merits) of PENELOPE as a track-structure code

Abstract: PENELOPE can be employed advantageously in some track-structure applications provided that the default model for inelastic interactions of electrons is replaced by suitable tables of differential and total cross sections.

Cited by 56 publications

References 18 publications

Dependence of gold nanoparticle radiosensitization on cell geometry

Dependence of gold nanoparticle radiosensitization on cell geometry

Monte Carlo Evaluation of Auger Electron–Emitting Theranostic Radionuclides

An implementation of discrete electron transport models for gold in the Geant4 simulation toolkit

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