background : in spite of clinically useful photon and electron beams, high energy linacs produce secondary particles such as neutrons (photo-neutron production). neutrons have important roles during treatment with high energy photons in terms of protection and dose escalation. in this project, neutron dose equivalent of 18 mv varian accelerators is calculated by tld600 and tld700. materials and...

We explore the NLC linac optics compatible with a low energy scenario where initially only part of the full linac is installed. Optics modification suitable for a low energy beam running and upgrade to the nominal energy is discussed. Linac parameters and beam tolerances in the modified lattice are compared to the nominal design. Abstract We explore the NLC linac optics compatible with a low en...

introduction: globally, the need for radiotherapy as a part of cancer management increases every year. thus, the shielding for megavoltage radiotherapy rooms is of great importance. materials and methods: in the present study, 14 types of developed high-density concrete with densities ranging from 2.45 to 5.11 were simulated by using monte carlo method. the linear attenuation coefficient and th...

The real-time operation of a linac-MRI system will require proper radio frequency (RF) shielding such that the MRI images can be acquired without extraneous RF noise from the linac. We report on the steps taken to successfully shield the linac from the MRI such that the two devices can operate independently of one another. RF power density levels are reported internally and externally to the RF...

Instruments. NMR spectra were obtained with Bruker AC-300 and Varian UNITY-500 spectrometers. Mass spectra were obtained with Perkin Elmer Sciex API 365 electrospray ionization (ESI) and Bruker Biflex III matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) instruments at the University of Wisconsin Biotechnology Center. Ultraviolet and visible absorbance was recorded with a C...

A non-physical wedge generates a spatial dose distribution similar to that produced by a physical wedge without a physical filter in the photon beam. Instead, an exponential fluence profile is produced via motion of one of the collimating jaws. Proposed in the late 1970s, nonphysical wedges have been implemented on both Varian and Siemens’ accelerators as the Varian Dynamic Wedge (DW) and Sieme...

Introduction: This study investigates basic dosimetric properties of unflattened 6 MV photon beam shaped by multileaf collimator and compares them with those of flattened beams.Materials and Methods: Monte Carlo simulation model using BEAM code was developed for a 6MV photon beam based on Varian Clinic 600 unique performance linac operated with and without a flattening filter in beam line. Dosi...

Background: External beam radiation therapy is often administered to patients implanted with silicone gel breast prosthesis. The aim of this study was to investigate the influence of silicone gel breast prosthesis on photon dose distributions. In the event of recurrence, the oncologist may be forced to irradiate through the prosthetic device. To quantify the dose enhancement or reduction below ...