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    Wyświetlanie 1-5 z 5
    Tytuł:
    Monte Carlo modeling of electron beams from a NEPTUN 10PC medical linear accelerator
    Autorzy:
    Jabbari, N.
    Hashemi-Malayeri, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/148140.pdf
    Data publikacji:
    2009
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    Monte Carlo
    radiotherapy
    electron beams
    linac
    Opis:
    The Monte Carlo (MC) simulation of radiation transport is considered to be one of the most accurate methods of radiation therapy dose calculation. With the rapid development of computer technology, MC-based treatment planning for radiation therapy is becoming practical. A basic requirement for MC treatment planning is a detailed knowledge of radiation beams of medical linear accelerators (linacs). A practical approach to acquire this knowledge is to perform MC simulation of radiation transport for linacs. The aims of this study were: modeling of the electron beams from the NEPTUN 10PC linear accelerator (linac) with the MC method, obtaining of the energy spectra of electron beams, and providing the phase-space files for the electron beams of this linac at different field sizes. Electron beams produced by the linac were modeled using the BEAMnrc MC system. Central axis depth-dose curves and dose profiles of the electron beams were measured experimentally and also calculated with the MC system for different field sizes and energies. In order to benchmark the simulated models, the percent depth dose (PDD) and dose-profile curves calculated with the MC system were compared with those measured experimentally with diode detectors in an RFA 300 water phantom. The results of this study showed that the PDD and dose-profile curves calculated by the MC system using the phase-space data files matched well with the measured values. This study demonstrates that the MC phase-space data files can be used to generate accurate MC dose distributions for electron beams from NEPTUN 10PC medical linac.
    Źródło:
    Nukleonika; 2009, 54, 4; 233-238
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The effect of external wedge on the photoneutron dose equivalent at a high energy medical linac
    Autorzy:
    Hashemi, , S. M.
    Raisali, G.
    Taheri, M.
    Majdabadi, A.
    Ghafoori, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/147071.pdf
    Data publikacji:
    2011
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    photoneutron
    linac
    polycarbonate (PC)
    external wedge
    radiotherapy
    Opis:
    Medical linacs used in radiotherapy produce bremsstrahlung spectra. In the energy range from 8 to 25 MV medical linacs produce, besides the clinically useful electron and photon beams, secondary neutrons. The aim of this study was to investigate the effect of an external wedge filter on the photoneutron dose equivalent produced by a medical linac at patient plane. Polycarbonate (PC) films were used for the determination of photoneutron dose equivalent produced by a Varian 2100 C/D linac working at 18 MV photon mode. Neutron dose equivalent was measured at distances 0, 10, 20 and 50 cm from the center of the X-ray beam for open field and after inserting a wedge filter. It was noted that by inserting the external wedge in the path of the X-ray beam, the photoneutron dose equivalent was increased compared to open field. It can be concluded that an external wedge, made from heavy materials may act like the other components of linac head, producing undesired photoneutrons and thus increasing patient dose.
    Źródło:
    Nukleonika; 2011, 56, 1; 49-51
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Recent achievements at TRIUMF
    Autorzy:
    Dutto, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/146201.pdf
    Data publikacji:
    2003
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    TRIUMF
    ISAC
    radioactive ion beams
    ISOL
    cyclotron
    linac
    Opis:
    A new series of experiments (mainly in astrophysics) began at TRIUMF in July 2001 when the ISAC-I linear accelerator started delivering radioactive ion beams (RIB) of energy up to 1.5 MeV/u. Since then the linac has operated reliably. Required improvements demand care during scheduled maintenance. More difficult was the smooth production of RIB with a 500 MeV proton beam on different target materials, where state-of-the-art techniques are being learned. Targets of CaO, Ta, SiC, Nb, and CaZrO3 have been used in combination with a surface ion source and incident proton currents up to 40 žA. Record radioactive beam intensities were achieved. A second target station is now being commissioned and will become operational during the fall of 2002. A superconducting linear accelerator extending the RIB energy to 6.5 MeV/u has recently been approved and is now being constructed (ISAC-II). A new 3500 m2 experimental building is being erected. A charge state booster, which will extend the mass range of the accelerated ions from A ? 30 to A ? 150, is also being commissioned. The 500 MeV cyclotron is being refurbished for reliability and upgraded to higher currents. A suitable operational beam tune for a total H- accelerated beam current of 300 žA has been commissioned and is now available to supply beam to four separate extraction proton lines simultaneously.
    Źródło:
    Nukleonika; 2003, 48,suppl.2; 159-163
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A study of the photoneutron dose equivalent resulting from a Saturne 20 medical linac using Monte Carlo method
    Autorzy:
    Hashemi, F.
    Hashemi-Malayeri, B.
    Raisali, G.
    Shokrani, P.
    Sharafi, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/148191.pdf
    Data publikacji:
    2007
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    photoneutron
    linac
    Monte Carlo method
    MCNP4C
    dose equivalent
    Opis:
    High energy linacs have several advantages including lower skin dose and higher dose rate at deep sighted tumors. But, at higher energies photonuclear reactions produce neutron contamination. Photoneutron contamination has been investigated from the early days of modern linacs. However, more studies have become possible using Monte Carlo codes developed in recent years. The aim of this study was to investigate the photoneutron spectrum and dose equivalent produced by an 18 MV Saturne linac at different points of a treatment room and its maze. The MCNP4C code was used to simulate the transport of photoneutrons produced by a typical 18 MV Saturne linac. The treatment room of a radiotherapy facility in which a Saturne 20 linac is installed was modeled. Neutron dose equivalent was calculated and its variations at various distances from the center of the X-ray beam was studied. It was noted that by increasing the distance from the center of the beam, fast neutrons decrease rapidly, but thermal neutrons do not change significantly. In addition, the photoneutron dose equivalent was lower for smaller fields. The fast photoneutrons were not recorded in the maze. It can be concluded that the fast photoneutrons are highly attenuated by concrete barrier, while the slow photoneutrons are increased. In addition, increasing the X-ray field size increases the photoneutron dose equivalent around the treatment room and maze. It seems that the walls play an effective role in increasing the photoneutron dose equivalent.
    Źródło:
    Nukleonika; 2007, 52, 1; 39-43
    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
      Wyświetlanie 1-5 z 5

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