نتایج جستجو برای: photon
تعداد نتایج: 70717 فیلتر نتایج به سال:
ntroduction: monte carlo simulation is the most accurate method of simulating radiation transport and predicting doses at different points of interest in radiotherapy. a great advantage of the monte carlo method compared to the deterministic methods is the ability to deal accurately with any complex geometry. its disadvantage is the extremely long computing time r...
background: physical wedges are still widely used as beam modifiers in external beam radiotherapy. however the presence of them in the beam trace may cause beam hardening which may not be considered in many treatment planning systems. the aim of this study is to investigate the beam hardening effect generated by physical wedges via different beam quality indexes as photon spectrum, half value l...
Using the effective Lagrangian for the low energy photon-photon interaction the lowest order photon self energy at finite temperature and in nonequilibrium is calculated within the real time formalism. The Debye mass, the dispersion relation, the dielectric tensor, and the velocity of light following from the photon self energy are discussed. As an application we consider the interaction of pho...
the cancer of oral cavity is related to lesions of mucous membrane of tongue and gum that can be treated with radiation therapy. a lateral photon field can be used to treat this kind of tumor, which has a side‑effect on normal tissue in the opposite side of the oral cavity. in this study the dosimetric effect of the various shields in oral cavity is evaluated. in this study, a special phantom s...
introduction : due to the importance of laser light penetration and propagation in biological tissues, many researchers have proposed several numerical methods such as monte carlo, finite element and green function methods. among them, the monte carlo method is an accurate method which can be applied for different tissues. however, because of its statistical nature, monte carlo simulation requi...
introduction: the photoelectric attenuation coefficient of substances is known to depend upon the energy e of the photon and the effective atomic number of substances (zeff) as (zeff x /e y ). no definitive values about these indices x, y are given in the literature. the index x is said to lie between, 3.0 and 4.0, while for ‘y’ different values have been assigned, between 3.0 and 4.0. methodo...
background: radiation shielding properties is an important for a material wish can be used the photon attenuation coefficients of clay produced using different rate of boron have been measured for the purpose of radioactive waste disposal. materials and methods: the measurement has been performed using gamma spectrometer contains nai (tl) detector at the photon energies of 662, 1173 and 1332 ke...
Background and purpose: Breast‑conserving surgery followed by radiation therapy to the whole breast is now recognized as a standard strategy in patients with breast cancer. Recommended technique for radiotherapy is whole breast irradiation followed by boost to the tumor bed. This study aimed to compare the dosimetric parameters of electron and photon beams for boosting irradiation in post‑lump...
Background: Physical wedges are still widely used as beam modifiers in external beam radiotherapy. However the presence of them in the beam trace may cause beam hardening which may not be considered in many treatment planning systems. The aim of this study is to investigate the beam hardening effect generated by physical wedges via different beam quality indexes as photon spectrum, half value l...
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