The application of small photon fields in modern radiotherapy requires the determination total scatter factors Scp or field Ω(f(clin), f(msr))(Q(clin), Q(msr)) with high precision. Both quantities require knowledge field-size-dependent and detector-dependent correction factor k(f(clin), Q(msr)). aim this study is for different types detectors a clinical 6 MV beam Siemens KD linear accelerator. EGSnrc Monte Carlo code was used to calculate dose water determine as well mentioned square sizes....

In 2016 the ICRU published a new report dealing with key data for ionizing radiation dosimetry (ICRU Report 90). New recommendations have been made mean excitation energies I air, graphite and liquid water as well density to use when evaluating effect. addition, 90 discusses renormalized photoelectric cross sections, but refuses give recommendation on of renormalization factors. However, Consultative Committee Ionizing Radiation recommends photoeffect sections. Goal present work is evaluate...

Purpose: Photon fields with energies above ∼7 MeV are contaminated by neutrons due to photonuclear reactions. Their influence on dosimetry—although considered be very low—is widely unexplored. Methods: In this work, Monte Carlo based investigations into issue performed fluka and egsnrc presented. A typical Linac head in 18 MV‐X mode was modeled equivalently within both codes. used for the photon neutron production transport simulation. Water depth dose profiles response of different...

The electron fluence inside a parallel-plate ionization chamber positioned in water phantom and exposed to clinical beam deviates from the unperturbed absence of chamber. One reason for perturbation is well-known "inscattering effect," whose physical cause lack scattering gas-filled cavity. Correction factors determined correct this effect have long been recommended. However, more recent Monte Carlo calculations led some doubt about range validity these corrections. Therefore, aim present...

Although several studies provide data for reference dosimetry, the SNC600c and SNC125c ionization chambers (Sun Nuclear Corporation, Melbourne, FL) are in clinical use worldwide which no beam quality correction factors kQ available. The goal of this study was to calculate these according dosimetry protocols TG-51, TRS 398 DIN 6800-2.Monte Carlo simulations using EGSnrc have been performed absorbed dose water air within active volume chamber models. Both spectra transport through linear...

The presence of an air filled ionization chamber in a surrounding medium introduces several fluence perturbations high energy photon and electron beams which have to be accounted for. One these perturbations, the displacement effect, may corrected two different ways: by correction factor pdis or application concept effective point measurement (EPOM). latter means, that volume averaged within is not reported chambers reference but cavity. Within this study EPOM was determined for four...

The use of small photon fields in modern radiotherapy requires the determination total scatter factors Scp or field factorswith high precision. Therefore, chamber-dependent correction for dose measurements are necessary. In this study Monte Carlo simulations were used to calculate factorand chamber response-related four different types detectors a clinical 6 MV beam square size 1 cm × cm. As source Carlo-based model Siemens KD linear accelerator was applied. calculations aimed at...

The impact of removing the flattening filter in clinical electron accelerators on relationship between dosimetric quantities such as beam quality specifiers and mean photon energies radiation field was investigated by Monte Carlo simulations. purpose this work to determine uncertainties when using well-known or energy-based predictors properties filter.Monte simulations applying eight different linear accelerator head models with without were performed order generate realistic sources...

Clinical dosimetry is typically performed using ion chambers calibrated in terms of absorbed dose to water. As primary measurement standards for this quantity low and medium energy x-rays are available only since a few years, most protocols photon range still based on air kerma calibration. For that reason, data beam quality correction factors [Formula: see text], necessary the application water protocols, scarce literature. Currently international IAEA TRS-398 Code Practice under revision...

The integration of magnetic resonance tomography into clinical linear accelerators provides high-contrast, real-time imaging during treatment and facilitates online-adaptive workflows in radiation therapy treatments. associated field also bends the trajectories charged particles via Lorentz force, which may alter dose distribution a patient or phantom affects response dosimetry detectors.To perform an experimental Monte Carlo-based determination correction factors kB,Q$k_{B,Q}$ , correct ion...

Monte Carlo simulations are crucial for calculating magnetic field correction factors kB the dosimetry in external fields. As codes charged particle transport is performed straight condensed history (CH) steps, curved trajectories of these particles presence fields can only be approximated. In this study, a strong B→ was investigated using Fano cavity test. The test an ionization chamber and diode detector, showing how step size restrictions must adjusted to perform consistent within all...

In radiotherapy, Monte Carlo (MC) methods are considered a gold standard to calculate accurate dose distributions, particularly in heterogeneous tissues. EURADOS organized an international comparison with six participants applying different MC models real medical linear accelerator and one homogeneous four dosimetric phantoms.The aim of this exercise was identify, by complete experimental dataset, critical aspects useful for users build calibrate simulation perform analysis.Results show on...

Multi-axis ionization chamber arrays can be used for quality assurance (QA) and measurement of linear accelerator (linac) specific data. In this work, the ability IC Profiler (Sun Nuclear Corp., Melbourne, Florida) detector array to measure photon beam specifier %dd(10) x$_\textrm {{\it x}}$ TPR20, 10 was investigated. To investigate method energy QA using a two-dimensional array, Monte Carlo-based model developed validated.A with Quad Wedge accessories in detail from drawings provided by...

As the dosimetry protocol TRS 398 is being revised and ICRU report 90 provides new recommendations for density correction as well mean ionization energies of water graphite, updated beam quality factors k

Purpose: National and international dosimetry protocols assume a position accuracy for ionization chambers of less than 0.2mm. To follow this precept the manufacturer PTW‐Freiburg introduced positioning assistance system (TRUFIX) their particular ion chambers. Aim study is an experimental investigation uncertainties ROOS‐type Methods: For all measurements linear accelerator Elekta Synergie was used. The experiments were performed in water‐phantom. collimate electron beam 10×10cm 2 applicator...

The aim of this study was to develop an algorithm that corrects the image electronic portal imaging device (EPID) a linear accelerator so it can be used for dosimetric purposes, such as in vivo dosimetry or quality assurance photon radiotherapy. For purpose, impact field size, phantom thickness, and varying spectral distribution within irradiation on EPID investigated.The measurements were verified using reference with ionization chambers. Therefore, absolute dose chamber relative detector...

Purpose: This paper aims to determine the effective point of measurement and total perturbation correction p parallel‐plate chambers for clinical photon dosimetry. Methods: The (EPOM) was calculated using EGSnrc Monte Carlo code system with user egs_ chamber. Depth dose curves ionization were in a water phantom several high energy spectra (4, 6, 10, 15, 18 MV‐X). Different normalization criterions (normalization maximum depth curve value 10 cm depth) have been applied. EPOM determined by...

Purpose: Developing a fast and accurate calculation model to reconstruct the applied photon fluence from an external radiation therapy treatment based on image recorded by electronic portal device (EPID). Methods: To initial 2D EPID was corrected for scatter patient/phantom generate transmitted primary fluence. This done iterative deconvolution using precalculated point spread functions (PSF). The then backprojected through geometry considering linear attenuation receive treatment.The...

Purpose: Alanine dosimeters are often used for in‐vivo dosimetry purposes in radiation therapy. In a Monte Carlo study the influence of 20 different surrounding/phantom materials alanine was investigated. The investigations were performed high‐energy photon beams, covering whole range from 60 Co up to 25 MV‐X. aim is introduction perturbation correction k env accounting environmental material. Methods: surrounding on response investigated with simulations using EGSnrc code. source adapted...