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    Wyświetlanie 1-10 z 10
    Tytuł:
    Dose enhancement in brachytherapy in the presence of gold nanoparticles : a Monte Carlo study on the size of gold nanoparticles and method of modelling
    Autorzy:
    Ghorbani, M.
    Pakravan, D.
    Bakhshabadi, M.
    Meigooni, A. S.
    Powiązania:
    https://bibliotekanauki.pl/articles/146605.pdf
    Data publikacji:
    2012
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    brachytherapy
    dose enhancement
    gold nanoparticles
    Monte Carlo (MC)
    Opis:
    The aim of this study was to evaluate the effect of the size of gold nanoparticles (GNPs) on dose enhancement in brachytherapy with photon emitting sources. Four photon emitting sources, 125I, 169Yb, 103Pd, and 192Ir were simulated and dose rate constant and radial dose functions were compared with published corresponding data for these sources. Dose enhancement factor in the presence of gold nanoparticles of 30 mg/ml concentration was calculated separately for nanoparticles with a diameter of 50, 100 and 200 nm. Gold nanoparticles were simulated precisely as nanospheres utilizing a lattice option in the MCNPX Monte Carlo code and the results were compared with those obtained with a simple model in which gold atoms are distributed uniformly in tumor volume as a simple mixture. Among the four mentioned sources, the dose enhancement related to 125I source is higher. Our results have shown that with gold nanoparticles of higher diameter, the level of dose enhancement is higher in the tested tumor. It has been also observed that the simple model overestimates the dose enhancement factor when compared with the precise model in which nanoparticles are defined according to the Monte Carlo code. In the energy range produced by the brachytherapy sources, the dose enhancement is higher when using brachytherapy sources with lower energy. Among the size range of gold nanoparticles used in medicine, it is predicted that nanoparticles with higher diameter can be more useful when are utilized in brachytherapy. It is also recommended that when calculating dose enhancements, a precise model be used for modelling of nanoparticles in the Monte Carlo simulations.
    Źródło:
    Nukleonika; 2012, 57, 3; 401-406
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Incrustation of alpha-particle emitters in the source backing: influence on activity measurements
    Autorzy:
    Jurado-Vargas, M.
    Fernández-Timón, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/146904.pdf
    Data publikacji:
    2012
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    alpha-particle spectrometry
    Monte Carlo (MC) simulation
    SRIM
    Opis:
    Alpha particles emitted from radioactive sources are often measured using a 2pi counting geometry in order to determine the activity with a low deviation. The ratio C2pi/A (counting rate/activity) can, however, deviate from the theoretical value of 0.5 because of backscattering in the backing material, scattering and absorption of alpha particles in the source. The experimental counting rates are, therefore, corrected for these effects (backscattering for all sources, plus self-absorption for sources of non-negligible thickness) to determine the real source activity. However, the corrections needed for situations corresponding to alpha-particle sources in which the radionuclides are not deposited but incrusted in the backing material have not been considered. The aim of the present work was therefore to study the influence that incrustation in the backing can have on the total detection efficiency, and hence on the activity estimated for the source. To this end, we used the Monte Carlo computer code SRIM to model the behaviour of the alpha particles in the backing material.
    Źródło:
    Nukleonika; 2012, 57, 4; 569-573
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Evaluation and benchmarking of gamma dose rate employing different nuclear data libraries for MCNP code at the decommissioning stage of Ignalina NPP
    Autorzy:
    Stankunas, G.
    Tonkunas, A.
    Pabarcius, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/146253.pdf
    Data publikacji:
    2011
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    dose rate
    Monte Carlo (MC)
    nuclear data libraries
    decommissioning
    Opis:
    A comparative study was performed to reveal the differences of three nuclear data libraries for gamma dose rate calculations when applied to heterogeneous environment in the case of decommission of the Ignalina Nuclear Power Plant (INPP). The following libraries were investigated by employing the Monte Carlo n-particle transport code (MCNP): ENDF/B-VII, JEFF-3.1 and JENDL-3.3, based on the experiments performed for gamma radiation dose rate measurements inside the emergency core cooling system (ECCS) tank with surface radioactive contamination up to 54 Bq/cm2. MCNP precise simulation and the benchmark between the libraries highlighted the differences of results for the selected case of this investigation. The results revealed that the ENDF library is trustworthy for various dose and shielding calculations and similar applications since it showed a statistically satisfied agreement between the simulation results and experimental data.
    Źródło:
    Nukleonika; 2011, 56, 1; 71-76
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Simulation of computed tomography (CT) images using a Monte Carlo approach
    Autorzy:
    Wysocka-Rabin, A. M.
    Qamhiyeh, S.
    Jäkel, O.
    Powiązania:
    https://bibliotekanauki.pl/articles/147601.pdf
    Data publikacji:
    2011
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    X-ray tomography
    Monte Carlo (MC) method
    treatment planning
    hadrontherapy
    Opis:
    Heavy ion treatment planning uses an empirical scanner-dependent calibration relation between computed tomography (CT) numbers and ion range. Any deviation in the values of CT numbers will cause a drift in the calibration curve of the CT scanner, which can reduce the accuracy of treatment beam delivery. To reduce uncertainty in the empirical estimation of CT numbers, we developed a simulation that takes into consideration the geometry, composition, and physical process that underlie their measurement. This approach uses Monte Carlo (MC) simulations, followed by a simple filtered back-projection reconstruction. The MC code used is BEAMnrc/EGSnrc. With the manufacturer’s permission, we simulated the components (X-ray tube, associated filters and beam shapers) of a Siemens Emotion CT. We then generated an initial beam shape and spectra, and performed further simulations using the phantom with substitutes. We analyzed the resulting phase space file to calculate projections, taking into account the energy response of the CT detectors. Then, we applied a simple reconstruction algorithm to the calculated projections in order to receive the CT image.
    Źródło:
    Nukleonika; 2011, 56, 4; 299-304
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Monte Carlo calculated CT numbers for improved heavy ion treatment planning
    Autorzy:
    Qamhiyeh, S.
    Wysocka-Rabin, A.
    Jäkel, O.
    Powiązania:
    https://bibliotekanauki.pl/articles/148658.pdf
    Data publikacji:
    2014
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    X-ray tomography
    Monte Carlo (MC) method
    treatment planning
    hadrontherapy
    Opis:
    Better knowledge of CT number values and their uncertainties can be applied to improve heavy ion treatment planning. We developed a novel method to calculate CT numbers for a computed tomography (CT) scanner using the Monte Carlo (MC) code, BEAMnrc/EGSnrc. To generate the initial beam shape and spectra we conducted full simulations of an X-ray tube, filters and beam shapers for a Siemens Emotion CT. The simulation output files were analyzed to calculate projections of a phantom with inserts. A simple reconstruction algorithm (FBP using a Ram-Lak filter) was applied to calculate the pixel values, which represent an attenuation coefficient, normalized in such a way to give zero for water (Hounsfield unit (HU)). Measured and Monte Carlo calculated CT numbers were compared. The average deviation between measured and simulated CT numbers was 4 ± 4 HU and the standard deviation σ was 49 ± 4 HU. The simulation also correctly predicted the behaviour of H-materials compared to a Gammex tissue substitutes. We believe the developed approach represents a useful new tool for evaluating the effect of CT scanner and phantom parameters on CT number values.
    Źródło:
    Nukleonika; 2014, 59, 1; 15-23
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Monte Carlo study on a new concept of a scanning photon beam system for IMRT
    Autorzy:
    Wysocka-Rabin, A. M.
    Hartmann, G. H.
    Powiązania:
    https://bibliotekanauki.pl/articles/147603.pdf
    Data publikacji:
    2011
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    Monte Carlo (MC) simulations
    medical accelerators
    intensity-modulated radiation therapy (IMRT)
    Opis:
    Intensity-modulated radiation therapy (IMRT) is almost exclusively realized using a multi-leaf collimator (MLC). In this work we investigated alternative approaches to realize an IMRT - scanning photon beam system. The technical realization of this concept required investigating the influence of various design parameters on the final small photon beam. This was done using Monte Carlo (MC) simulation methods. The resulting photon beam that is to be scanned should have a diameter well less than 10 mm at a source-surface distance (SSD), and the penumbra should be as small as possible. A first draft for this system, based on the PRIMUS 6 MV accelerator at DKFZ (Deutsches Krebsforshungszentrum), was proposed and modeled using the BEAMnrc/EGSnrc MC code. We then proposed and studied a new geometry of the source-target-collimator system. Calculations were done for 108 particles, using an electron energy cut-off (ECUT) = 0.7 MeV, and a photon energy cut-off (PCUT) = 0.01 MeV. The influence of different collimator parameters, different target construction and various incident electron beam characteristics was studied. Calculations of the dose absorbed in the water were performed for 8 different collimators at a distance of 40 cm from the collimator exit, which is the medical requirement. Results of the dose distribution calculations are presented as photon beam profiles with the values of full width at half-maximum (FWHM) and penumbra (PM) for every beam profile. The influence of target construction was studied for different thicknesses of target and material minimizing electron contamination. The influence of the following characteristics of the incident electron beam was also investigated: size of electron beam, energy, displacement of the beam from the axis of target-collimator system, shape of the electron beam profile. The field dose distribution of the photon beam was calculated for the collimators giving the beam profiles. Basing on the work performed in this investigation, it will be possible to define adequate parameters for the target-collimator system as well as on the scanning electron beam for new IMRT system.
    Źródło:
    Nukleonika; 2011, 56, 4; 291-297
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Development of the technique embedded into a Monte Carlo transport system for calculation of photonuclear isotope yield
    Autorzy:
    Nikiforov, V. I.
    Uvarov, V. L.
    Powiązania:
    https://bibliotekanauki.pl/articles/147914.pdf
    Data publikacji:
    2012
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    electron accelerator
    bremsstrahlung
    photonuclear reaction
    Monte Carlo (MC) simulation
    isotope yield
    Opis:
    The paper describes two methods that use Monte Carlo transport code for computing the photonuclear isotope yield for arbitrary target activation conditions. One of them is based on a direct simulation of new nuclei generation events (DSE method). The other one involves a step-by-step calculation of isotope microyield along the photon trajectories (SBSM method). The techniques have been realized in the computer codes using the PENELOPE package of 2001, 2006 and 2008 versions. The program benchmarking was performed using experimental data on the activity distributions of 67Cu isotope produced in the 68Zn(gamma,p)67Cu reaction in thick zinc targets. Both approaches have shown to give similar results at an appreciably greater speed of the SBSM method. The results of simulation based on the PENELOPE 2006 and 2008 codes are in excellent agreement with all experimental data. At the same time, the PENELOPE 2001 computations give good agreement with the experimental results for target activation by the electron beam, but in the case of target exposed to bremsstrahlung systematic underestimation of about 15% has been observed.
    Źródło:
    Nukleonika; 2012, 57, 1; 75-80
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Assessment of the staff absorbed dose related to cyclotron operation and service in the production of 18F radiopharmaceuticals
    Autorzy:
    Sadat-Eshkevar, S. M.
    Karimian, A.
    Mirzaii, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/146607.pdf
    Data publikacji:
    2012
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    staff dosimetry
    Monte Carlo (MC) simulation
    18F production
    cyclotron
    induced radioactivity
    liquid target
    Opis:
    Cyclotron accelerators are used to produce medical radioisotopes. One of the most important problems which may be encountered is malfunction of a part of the target or beam line which requires stopping of the bombardment and making a repair. The decision about doing the repair depends on the whole body dose rate in a target room. In this work, dosimetric conditions related to the production of 18FDG radiopharmaceutical were simulated by the Monte Carlo (MC) method. Independently, the dose rates were measured by 7 ICRU spherical body phantoms placed inside the liquid target room and the maze of the cyclotron. The radiation dose rate inside the target room depends on the duration of the bombardment and the time passed after stopping the bombardment. The correlation between duration of the bombardment and required time after stopping the bombardment to reach the absorbed dose rate less than 25 mi Sv/h, was calculated for the presence and absence of the irradiated target. The results showed that the repair can be started immediately after stopping of the proton bombardment only if the target has been ejected from the target room and the duration of bombardment has not taken more than 10 min.
    Źródło:
    Nukleonika; 2012, 57, 3; 407-410
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Tumor dose enhancement by gold nanoparticles in a 6 MV photon beam: a Monte Carlo study on the size effect of nanoparticles
    Autorzy:
    Pakravan, D.
    Ghorbani, M.
    Momennezhad, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/146977.pdf
    Data publikacji:
    2013
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    Monte Carlo (MC) simulation
    medical linac
    dose enhancement
    gold nanoparticle (GNP)
    flattening filter free (FFF)
    Opis:
    In this study after benchmarking of Monte Carlo (MC) simulation of a 6 MV linac, the simulation model was used for estimation of tumor dose enhancement by gold nanoparticles (GNPs). The 6 MV photon mode of a Siemens Primus linac was simulated and a percent depth dose and dose profiles values obtained from the simulations were compared with the corresponding measured values. Dose enhancement for various sizes and concentrations of GNPs were studied for two cases with and without the presence of a flattening filter in the beam’s path. Tumor dose enhancement with and without the presence of the flattening filter was, respectively 1–5 and 3–10%. The maximum dose enhancement was observed when 200 nm GNPs was used and the concentration was 36 mg/g tumor. Furthermore, larger GNPs resulted in higher dose values in the tumor. After careful observation of the dose enhancement factor data, it was found that there is a poor relation between the nanoparticle size and dose enhancement. It seems that for high energy photons, the dose enhancement is more affected by the concentration of nanoparticles than their size.
    Źródło:
    Nukleonika; 2013, 58, 2; 275-280
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Implementation of a Monte Carlo method to a two-dimensional particle-in-cell solver using algebraic meshes
    Autorzy:
    Sengil, N.
    Tümüklü, Ö.
    Çelenligil, M. C.
    Powiązania:
    https://bibliotekanauki.pl/articles/146470.pdf
    Data publikacji:
    2012
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    particle-in-cell (PIC)
    plasma flows
    Monte Carlo (MC) method
    coordinate transformation
    Poisson's equation
    Boltzmann relation
    Opis:
    Particle-in-cell (PIC) technique is a widely used computational method in the simulation of low density collisionless plasma flows. In this study, a new two-dimensional (2-D) electrostatic particle-in-cell solver is developed that can be applied to non-rectangular configurations.
    Źródło:
    Nukleonika; 2012, 57, 2; 313-316
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-10 z 10

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