نتایج جستجو برای: wedge based three fields
تعداد نتایج: 4061128 فیلتر نتایج به سال:
abstract the present study investigated the effects of task types and involvement load hypothesis on incidental learning of 10 target words (tws) in junior high schools (jhss) in givi, ardabil. the tasks deployed in this study were two input-based tasks (reading plus dictionary use with an involvement index of 3, and reading plus gap-fill task with an involvement index of 2), and one output-ba...
Background: The presence of a wedge filter in the beam trajectory can modify the beam quality and cause some changes in the dosimetry parameters which are usually difficult to be measured directly and accurately. Material and Methods: In this study the MCNP-4C Monte Carlo code was used to simulate the 9 MV photon beam generated by a linear accelerator. Upon getting a good agreement bet...
BACKGROUND Wedge filters are commonly used in radiation oncology for eliminating hot spots and creating a uniform dose distribution in optimizing isodose curves in the target volume for clinical aspects. These are some limited standard physical wedges (15°, 30°, 45°, 60°),or creating an arbitrary wedge angle, like motorized wedge or dynamic wedge,... The new formulation is presented by the comb...
Introduction: Physical wedge by modify photon beam shape and intensity has been utilized in radiotherapy to obtain uniformly dose distribution in tumor site with reduced hot spots. Calculation of dosimetric parameters for both symmetric and asymmetric wedged fields is proved necessary during linear accelerator (Linac) commissioning. The present study aimed to achieve o...
Some modern treatment-planning systems (TPSs) provide for input of wedge factor (WF) tables covering the entire range of square and elongated fields available on the LINAC. Depending on the field size increment chosen and the number of available wedge orientations, one may have to take more than 100 measurements per wedge and photon energy to commission the TPS. To expedite TPS commissioning wh...
the purpose of this study is identifying effective factors which make customers shop online in iran and investigating the importance of discovered factors in online customers’ decision. in the identifying phase, to discover the factors affecting online shopping behavior of customers in iran, the derived reference model summarizing antecedents of online shopping proposed by change et al. was us...
the world wide web becomes very popular recently and plays an influential role in english learning. by burgeoning role of source-based writing as partial fulfillment of tefl courses and vast use of the internet, lack of empirical studies to explore these areas is obvious. this study aimed to explore the effect of the amount of familiarity with the web (internet literacy) on junior english stude...
Introduction: Physical wedge as a useful tool has been utilized in radiotherapy to modify photon beam shape and intensity such that it distributes dose uniformly in tumor site and reduces hot points. Since during Linac commissioning dosimetric parameters like output factors and lateral dose profiles are measured only for symmetric open and wedged fields, so calculation the par...
A novel MatLab-based diffraction tool for the investigation of scattered fields around a two-dimensional Perfectly Electric Conductor (PEC) wedge is introduced. Analytical (Exact by Integral, as well as some High Frequency Asymptotic (HFA) techniques) and numerical (Finite-Difference Time-Domain (FDTD)) models are included. The FDTD staircase modeling problems are removed by the application of ...
Introduction: In 3DCRT the number of therapeutic fields has dramatic impact on treatment results especially in stomach cancer. Traditionally, for radiotherapy of stomach cancer the therapeutic procedure was using two fields (AP- PA or AP Lateral with wedge) to achieve smooth and homogeneous dose distribution in tumor. But nowadays, adding lateral or oblique fields to aforement...
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