نتایج جستجو برای: megavoltage photons

تعداد نتایج: 47760  

ژورنال: سنجش و ایمنی پرتو 2017

Recent studies suggest that relative biological damage (RBD) may change from in to out of field regions for 6 MV photon beams. In this study RBD was calculated in and out of field of 30x30 cm2 and 40x40 cm2 6 MV clinical photon beams including low energy slowing down electrons in track length estimated method. Varian 2100C/D linear accelerator was simulated using MCNPX code. Electron and photon...

A. Shams, H. Shahbazian, M.A. Behrooz, M.J. Tahmasebi Birgani,

Background: Attenuation coefficient (μ) plays an important role in calculations of treatment planning systems, as well as determination of dose distributions in external beam therapy, dosimetry, protection, phantom materials and industry. So, its exact measurement or calculation is very important. The aim of this study was to evaluate the μ in different points in the water phantom anal...

Journal: :Communications physics 2021

Abstract Very high energy electron (VHEE) beams have been proposed as an alternative radiotherapy modality to megavoltage photons; they penetrate deeply without significant scattering in inhomogeneous tissue because of their relativistic inertia. However, the depth dose distribution a single, collimated VHEE beam is quasi-uniform, which can lead healthy being overexposed. This be largely overco...

Journal: :Medical physics 2014
Benigno Barbés Juan D Azcona Javier Burguete Josep M Martí-Climent

PURPOSE External beam radiation therapy (EBRT) usually uses heterogeneous dose distributions in a given volume. Designing detectors for quality control of these treatments is still a developing subject. The size of the detectors should be small to enhance spatial resolution and ensure low perturbation of the beam. A high uniformity in angular response is also a very important feature in a detec...

Journal: :Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology 1998
A Nisbet D I Thwaites M E Sheridan

BACKGROUND AND PURPOSE A comprehensive dosimetry intercomparison has been carried out involving all the radiotherapy centres, all external beam modalities and every radiotherapy treatment unit in the Republic of Ireland. MATERIALS AND METHODS Reference point measurements were made for all megavoltage photon beams. Doses were also investigated in planned three-field distributions. One of these...

Mohammad Amin Mosleh-Shirazi, Sahar Ranjbar Sareh Karbasi, Somayeh Gholami, Zinat Zarrini-Monfared

  Introduction: Arrays of segmented scintillation crystals are useful in megavoltage x-ray imaging detectors for image-guided radiotherapy. Most previous theoretical studies on these detectors have modelled only ionizing-radiation transport. Scintillation light also affects detector performance. ScintSim1, our previously reported optical Monte Carlo code for such detector...

Journal: :Journal of biomedical optics 2013
Rongxiao Zhang David J Gladstone Lesley A Jarvis Rendall R Strawbridge P Jack Hoopes Oscar D Friedman Adam K Glaser Brian W Pogue

Cherenkov radiation is induced when charged particles travel through dielectric media (such as biological tissue) faster than the speed of light through that medium. Detection of this radiation or excited luminescence during megavoltage external beam radiotherapy (EBRT) can allow emergence of a new approach to superficial dose estimation, functional imaging, and quality assurance for radiation ...

2009
Christopher F Njeh Timothy W Raines Mark W Saunders

Highly attenuating radiation treatment couches are no longer useful in the present era of radiotherapy utilizing IMRT and IGRT. Carbon fibers couch tops with its high tensile strength and low density present a useful alternative. The objective of the current study was to quantify the attenuation of megavoltage photons through a Brainlab imaging couch top and headrest at various angles and field...

Journal: Nanomedicine Journal 2018

Objective(s): Taking advantage of high atomic number of gold nanoparticles (GNPs) in radiation dose absorbing, many in vitro and in vivo studies have been carried out on using them as radio-sensitizer. In spite of noticeable dose enhancement by GNPs at keV energies, using this energy range for radiotherapy of deep-seated tumors is outdated. The aim of the present work was to examine the effect ...

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