95 research outputs found
Comment on "Reproducibility study of Monte Carlo simulations for nanoparticle dose enhancement and biological modeling of cell survival curves" by Velten et al. [Biomed Phys Eng Express 2023;9:045004]
This comment highlights two methodological issues with the recent article by
Velten et al. [Biomed Phys Eng Express 2023;9:045004]Comment: 4 pages, no figures, submitted to Biomed Phys Eng Expres
EURADOS Working Group 6, Computational Dosimetry, a history of promoting good practice via intercomparisons and training
This paper is the editorial of a special issue of Radiation Measurements on
EURADOS intercomparisons in computational dosimetry. The articles in this
special issue cover complex problems in terms of geometry, particle types,
energy ranges, coupled calculations and also scale, with the possibility of
performing Monte Carlo calculations on micro and nano dosimetric scales now
feasible. A summary of the exercises is provided in the first article of the
Special Issue, which presents the findings and common conclusions from the ten
articles reporting the results of the different exercises. One of these issues
was the correct assessment of bone marrow dose, which prompted the inclusion of
an article in this special issue explaining the ICRP-recommended method for
bone marrow dosimetry.Comment: 5 page
Article Commentary on "Microdosimetric and radiobiological effects of gold nanoparticles at therapeutic radiation energies" [T.M. Gray et al., IJRB 2023, 99(2), 308-317]
In the recently published article by T.M. Gray et al. "Microdosimetric and
radiobiological effects of gold nanoparticles at therapeutic radiation
energies" (IJRB 2023, 99(2), 308-317) results of Monte Carlo simulations and
radiobiological assays on the dosimetric effects of gold nanoparticles were
presented. This commentary points out that the results of the two parts of the
study are in contradiction and that the predicted magnitude of dose enhancement
and its dependence on the shape of the nanoparticle appear implausible.
Possible reasons for these observations are discussed.Comment: 19 pages, 4 figures, 2 tables. Submitted to IJR
Secondary ionisations in a wall-less ion-counting nanodosimeter: quantitative analysis and the effect on the comparison of measured and simulated track structure parameters in nanometric volumes
The object of investigation in nanodosimetry is the physical characteristics of the microscopic structure of ionising particle tracks, i.e. the sequence of the interaction types and interaction sites of a primary particle and all its secondaries, which reflects the stochastic nature of the radiation interaction. In view of the upcoming radiation therapy with protons and carbon ions, the ionisation structure of the ion track is of particular interest. Owing to limitations in current detector technology, the only way to determine the ionisation cluster size distribution in a DNA segment is to simulate the particle track structure in condensed matter. This is done using dedicated computer programs based on Monte Carlo procedures simulating the interaction of the primary ions with the target. Hence, there is a need to benchmark these computer codes using suitable experimental data. Ionisation cluster size distributions produced in the nanodosimeter\u27s sensitive volume by monoenergetic protons and alpha particles (with energies between 0.1 MeV and 20 MeV) were measured at the PTB ion accelerator facilities. C3H8 and N2 were alternately used as the working gas. The measured data were compared with the simulation results obtained with the PTB Monte-Carlo code PTra [B. Grosswendt, Radiat. Environ. Biophys. 41, 103 (2002); M.U. Bug, E. Gargioni, H. Nettelbeck, W.Y. Baek, G. Hilgers, A.B. Rosenfeld, H. Rabus, Phys. Rev. E 88, 043308 (2013)]. Measured and simulated characteristics of the particle track structure are generally in good agreement for protons over the entire energy range investigated. For alpha particles with energies higher than the Bragg peak energy, a good agreement can also be seen, whereas for energies lower than the Bragg peak energy differences of as much as 25% occur. Significant deviations are only observed for large ionisation cluster sizes. These deviations can be explained by a background consisting of secondary ions. These ions are produced in the region downstream of the extraction aperture by electrons with a kinetic energy of about 2.5 keV, which are themselves released by ions of the primary ionisation cluster hitting an electrode in the ion transport system. Including this background of secondary ions in the simulated cluster size distributions leads to a significantly better agreement between measured and simulated data, especially for large ionisation clusters. Graphical abstract: [Figure not available: see fulltext.
Secondary ionisations in a wall-less ion-counting nanodosimeter: quantitative analysis and the effect on the comparison of measured and simulated track structure parameters in nanometric volumes
The object of investigation in nanodosimetry is the physical characteristics of the microscopic structure of ionising particle tracks, i.e. the sequence of the interaction types and interaction sites of a primary particle and all its secondaries, which reflects the stochastic nature of the radiation interaction. In view of the upcoming radiation therapy with protons and carbon ions, the ionisation structure of the ion track is of particular interest. Owing to limitations in current detector technology, the only way to determine the ionisation cluster size distribution in a DNA segment is to simulate the particle track structure in condensed matter. This is done using dedicated computer programs based on Monte Carlo procedures simulating the interaction of the primary ions with the target. Hence, there is a need to benchmark these computer codes using suitable experimental data. Ionisation cluster size distributions produced in the nanodosimeter\u27s sensitive volume by monoenergetic protons and alpha particles (with energies between 0.1 MeV and 20 MeV) were measured at the PTB ion accelerator facilities. C3H8 and N2 were alternately used as the working gas. The measured data were compared with the simulation results obtained with the PTB Monte-Carlo code PTra [B. Grosswendt, Radiat. Environ. Biophys. 41, 103 (2002); M.U. Bug, E. Gargioni, H. Nettelbeck, W.Y. Baek, G. Hilgers, A.B. Rosenfeld, H. Rabus, Phys. Rev. E 88, 043308 (2013)]. Measured and simulated characteristics of the particle track structure are generally in good agreement for protons over the entire energy range investigated. For alpha particles with energies higher than the Bragg peak energy, a good agreement can also be seen, whereas for energies lower than the Bragg peak energy differences of as much as 25% occur. Significant deviations are only observed for large ionisation cluster sizes. These deviations can be explained by a background consisting of secondary ions. These ions are produced in the region downstream of the extraction aperture by electrons with a kinetic energy of about 2.5 keV, which are themselves released by ions of the primary ionisation cluster hitting an electrode in the ion transport system. Including this background of secondary ions in the simulated cluster size distributions leads to a significantly better agreement between measured and simulated data, especially for large ionisation clusters. Graphical abstract: [Figure not available: see fulltext.
Experimental benchmark data for Monte Carlo simulated radiation effects of gold nanoparticles. Part I: Experiment and raw data analysis
Electron emission spectra of gold nanoparticles (AuNPs) after photon
interaction were measured over the energy range between 50 eV and 9500 eV to
provide reference data for Monte Carlo radiation-transport simulations.
Experiments were performed with the HAXPES spectrometer at the PETRA III
high-brilliance beamline P22 at DESY (Hamburg, Germany) for photon energies
below and above each of the gold L-edges, i.e., at 11.9 keV, 12.0 keV, 13.7
keV, 13.8 keV, 14.3 keV, and 14.4 keV. The study focused on a sample with gold
nanoparticles with an average diameter of 11.0 nm on a thin carbon foil.
Additional measurements were performed on a sample with 5.3 nm gold
nanoparticles and on reference samples of gold and carbon foils. Further
measurements were made to calibrate the photon flux monitor, to characterize
the transmission function of the electron spectrometer and to determine the
size of the photon beam. This allowed the determination of the absolute values
of the spectral particle radiance of secondary electrons per incident photon
flux. The paper presents the experimental and raw data analysis procedures,
reviews the data obtained for the nanoparticle samples and discusses their
limitations.Comment: 18 pages, 13 Figures, 6 Tables plus 4 Supplements with altogether 14
pages, 16 figures, 2 table
Experimental benchmark data for Monte Carlo simulated radiation effects of gold nanoparticles. Part II: Comparison of measured and simulated electron spectra from gold nanofoils
Electron emission spectra of a thin gold foil after photon interaction were
measured over the energy range between 50 eV and 9500 eV to provide reference
data for Monte Carlo radiation-transport simulations. Experiments were
performed with the HAXPES spectrometer at the PETRA III high-brilliance
beamline P22 at DESY (Hamburg, Germany) for photon energies just below and
above each of the gold L-edges, i.e., at 11.9 keV, 12.0 keV, 13.7 keV, 13.8
keV, 14.3 keV, and 14.4 keV. The data were analyzed to obtain the absolute
values of the particle radiance of the emitted electrons per incident photon
flux. Simulations of the experiment were performed using the Monte Carlo
radiation-transport codes Penelope and Geant4. Comparison of the measured and
simulated results shows good qualitative agreement. When simulation results are
convolved with curves that take into account the effect of lifetime broadening,
line shapes of photoelectron and Auger peaks similar to those observed
experimentally are obtained. On an absolute scale, the experiments tend to give
higher electron radiance values at the lower photon energies studied as well as
at the higher photon energies for electron energies below the energy of the Au
L3 photoelectron. This is attributed to the linear polarization of the photon
beam in the experiments which is not considered in the simulation codes.Comment: Revised manuscript after peer review, 13 pages, 9 figure
Experimental benchmark data for Monte Carlo simulated radiation effects of gold nanoparticles. Part II: comparison of measured and simulated electron spectra from gold nanofoils
Electron emission spectra of a thin gold foil after photon interaction were measured over the energy range between 50 eV and 9500 eV to provide reference data for Monte Carlo radiation-transport simulations. Experiments were performed with the HAXPES spectrometer at the PETRA III high-brilliance beamline P22 at DESY (Hamburg, Germany) for photon energies just below and above each of the gold L-edges, that is, at 11.9 keV, 12.0 keV, 13.7 keV, 13.8 keV, 14.3 keV, and 14.4 keV. The data were analyzed to obtain the absolute values of the particle radiance of the emitted electrons per incident photon flux. Simulations of the experiment were performed using the Penelope and Geant4 Monte Carlo radiation-transport codes. Comparison of the measured and simulated results shows good qualitative agreement. On an absolute scale, the experiments tend to produce higher electron radiance values at the lower photon energies studied as well as at the higher photon energies for electron energies below the energy of the Au L3 photoelectron. This is attributed to the linear polarization of the photon beam in the experiments, something which is not considered in the simulation codes
Kinematically Complete Study of Low-Energy Electron-Impact Ionization of Neon: Internormalized Cross Sections in Three-Dimensional Kinematics
Low-energy (E0 0=65eV) electron-impact single ionization of Ne (2p) has been investigated to thoroughly test state-of-the-art theoretical approaches. The experimental data were measured using a reaction microscope, which can cover nearly the entire 4π solid angle for the secondary electron emission energies ranging from 2 to 8 eV, and projectile scattering angles ranging from 8.5⁰ to 20.0⁰. The experimental triple-differential cross sections are internormalized across all measured scattering angles and ejected energies. The experimental data are compared to predictions from a hybrid second-order distorted-wave Born plus R-matrix approach, the distorted-wave Born approximation with the inclusion of postcollision interaction (PCI), a three-body distorted-wave approach (3DW), and a B-spline R-matrix (BSR) with pseudostates approach. Excellent agreement is found between the experiment and predictions from the 3DW and BSR models, for both the angular dependence and the relative magnitude of the cross sections in the full three-dimensional parameter space. The importance of PCI effects is clearly visible in this low-energy electron-impact ionization process
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