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...

Introduction: A dosimetric audit is a quality assurance process (QA) that allows the accuracy of dosimetric and geometric precision to accurately control the delivery of doses. They can be used to evaluate the accuracy of radiation delivery at different radiotherapy centers. Differences in prescriptive doses, depending on the severity of the differences, have potential conseque...

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...

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...

In external beam radiation therapy (EBRT), the quality assurance (QA) of the radiation beam is crucial to the accurate delivery of the prescribed dose to the patient. One of the dosimetric parameters that require monitoring is the beam output, specified as the dose rate on the central axis under reference conditions. The aim of this project was to validate dose rate calibration of megavoltage p...

Background: Small-field dosimetry remains an open challenge globally. Thus, it is crucial to consider adequate reference codes of practice for the performance dosimetry. Furthermore, as part good clinical practice, implementation new implies development a audit program. In this work, pilot dosimetric protocol established measuring absolute dose in water small fields using micro-TLDs LiF:Mg,Ti d...

A practical and accurate generalized procedure to reconstruct the isocenter dose D(iso) for 3D conformal radiotherapy (3DCRT) has been developed for X-ray open beams supplied by linacs of different manufacturers and equipped with aSi electronic portal imaging devices (aSi EPIDs). This paper reports an extension of the method, to be applied at the wedged X-ray beams characterized by the wedge at...

BACKGROUND AND PURPOSE The QA of intensity modulated radiotherapy (IMRT) dosimetry is a laborious task. The goal of this work is to evaluate the dosimetric characteristics of a new 2D diode array (MapCheck from Sun Nuclear Corporation, Melbourne, Florida) and assess the role it can play in routine IMRT QA. MATERIAL AND METHODS Fundamental properties of the MapCheck such as reproducibility, li...

Background and purpose: Audit is imperative in delivering consistent and safe radiotherapy and the UK has a strong history of radiotherapy audit. The National Physical Laboratory (NPL) has undertaken audit measurements since 1994 and this work examines results from these audits. Materials and methods: This paper reviews audit results from 209 separate beams from 82 on-site visits to National He...

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...