Objective: Using Megavoltage photons generated by medical linear accelerator is a common modality for the treatment of malignant. The crucial problem for using photon beams >8MV is the photoneutron yields that increase the risk of secondary cancer that treated with high-energy photon beams. The contaminated neutrons produced in different components of the accelerator head and rely on many param...

the monte carlo method can be used to describe any technique that approximates solutions to quantitative problems through statistical sampling. this method is considered to be the most accurate method for dose calculation in radiotherapy. for complete modeling of a linear accelerator, it is required that the manufactured information covers all data, but some data such as primary electron energy...

background: monte carlo method (mc) has played an important role in design and optimization of medical linacs head and beam modeling. the purpose of this study was to compare photon beam features of two commercial linacs, varian 21ex and elekta sl-25 using mcnp4c mc code. materials and methods: the 6mv photon beams of varian 21ex and elekta sl-25 linacs were simulated based on manufacturers pro...

A description is given of the UK primary standard graphite calorimeter system. The calorimeter measures absorbed dose to graphite for photon radiations from 60Co to 19 MV x-rays, and is the basis of the NPL therapy-level absorbed dose to water calibration service. Absorbed dose to graphite from the photon calorimeter has been compared with three other standards: an ionization chamber and cavity...

Introduction: During intensity modulated radiation therapy (IMRT) technique, theoretically, presence of flattening filter (FF) across the beamline of clinical linear accelerator (linac) is not essential to obtain uniform lateral profiles due to intensity modulation of photon beams by multileaf collimators (MLCs). The aim of this study was to investigate the dosimetrical propert...

Background: During intensity modulated radiation therapy (IMRT) technique, theoretically, presence of flattening filter (FF) across the beamline of clinical linear accelerator (linac) is not essential to obtain uniform lateral profiles due to intensity modulation of photon beams by multileaf collimators (MLCs). The aim of this study was to investigate the dosimetrical properties of 18 MV photon...

Objective The aim of the present study is to simulate 6 MV and 18 MV photon beam energies of a Siemens Primus Plus medical linear accelerator (Linac) and to verify the simulation by comparing the results with the measured data. Methods The main components of the head of Siemens Primus Plus linac were simulated using MCNPX Monte Carlo (MC) code. To verify the results, experimental data of perc...

The inverse problem formulation of the depth dose curve estimation is applied to sparse non-equally spaced measurement grid and the subsequent solution as well as the selection of measurement depths are discussed. The performance of the proposed estimation method is evaluated with real 6 MeV and 18 MeV photon data. These studies show that the proposed method allows the estimation of the depth d...

background: accurate small radiation field dosimetry is essential in modern radiotherapy techniques such as stereotactic radiosurgery (srs) and intensity modulated radiotherapy (imrt). precise measurement of dosimetric parameters such as beam profile, percentage depth doses and output factor of these beams are complicated due to the electron disequilibrium and the steep dose gradients. in the p...

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...