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: the electron contamination may reduce or even diminish the skin sparing property of the megavoltage beam. the detailed characteristics of contaminant electrons are presented for different field sizes and cases. materials and methods: the monte carlo code, mcnpx, has been used to simulate 18 mv photon beam from a varian linac-2300 accelerator. all dose measurements were carried out u...

introduction: this study was designed to evaluate dosimetric parameters such as rectal dose, bladder dose, integral dose (id), homogeneity index (hi) and conformity index (ci) in various treatment plans for prostate cancer. materials and methods: pelvic computed tomography (ct) scans of 27 patients were acquired and transferred to the rtdoseplan treatment planning system. for each patient, 8 co...

Background: Multiple beams are generally used with an increased possibility that the beam axis intersects the treatment table. Treatment tabletops are commonly made of carbon fiber due to its high mechanical strength and rigidity, low specific density, extremely light and low radiation beam attenuation properties. Purpose of this paper is investigated the dose changes in the buildup region and ...

Introduction: This study was designed to evaluate dosimetric parameters such as rectal dose, bladder dose, integral dose (ID), homogeneity index (HI) and conformity index (CI) in various treatment plans for prostate cancer. Materials and Methods: Pelvic computed tomography (CT) scans of 27 patients were acquired and transferred to the RTDosePLAN treatment planning system. For each patient, 8 co...

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...

introduction: esophageal cancer is one of the most frequently occurring cancers in iran and having a  high  incidence  rate  among  other  countries.  radiotherapy  is  one  of  the  three  methods  (surgery,  radiotherapy and chemotherapy) for radical or palliative treatment of esophageal cancer. in this method  of treatment, the organs such as heart and spinal cord are regarded as organs at r...

Background: Skyshine describes the radiation scattered by the atmosphere above a LINAC facility to a point on the ground. The aim of this study was to measure the skyshine photon dose rates from two different (9 MV and 18 MV) medical linear accelerators. Materials and Methods: The photon beam was directed upward (180° gantry position), with a maximum photon field size (40 × 40 cm2) at the isoce...

Purpose: Fiber carbon is the most common material used in treating couch as it causes less beam attenuation than other materials. Beam attenuation replaces build-up region, reduces skin-sparing effect and causes target volume under dosage. In this study, we aimed to evaluate beam attenuation and variation of build-up region in 550 TxT radiotherapy couch.Materials and Methods: In this study, we ...

background: to analyze the dosimetric and radio biologic advantages between intensity modulated radiotherapy (imrt) and 3 dimensional conformal radiotherapy (3dcrt) and selection of optimal photon energy for imrt treatments. material and methods: 24 patients with localized prostate carcinoma were planned for 3dcrt and imrt techniques. radiation dose of 54 gy with 2 gy/fraction, was planned to p...