Search results for "Carlo"
showing 10 items of 1845 documents
SU-FF-T-13: Monte Carlo Calculation of the TG-43 Dosimetric Parameters of a New BEBIG Ir-192 HDR Source
2005
Purpose: High dose rate (HDR) brachytherapy is a highly extended practice in clinical brachytherapy today. Quality dose rate distribution datasets of the HDR sources used in a clinical treatment are required. Because of the different source designs, a specific dosimetry dataset is required for each source model. In the recently published BRAPHYQS-ESTRO Report, an overview of available dosimetric data for all HDR Ir-192 sources is given, pointing out the lack of data for one of the sources, the used by the BEBIG MultiSource afterloading system (BEBIG GmbH, Germany). The purpose of this study is to obtain detailed dose rate distributions in liquid water media around this source. Material and …
SU-FF-T-329: Monte Carlo Dosimetric Study of the Flexisource Ir-192 HDR Source
2006
Purpose:Brachytherapy with high dose rate (HDR) sources of 192 Ir is a usual practice in clinical brachytherapy today. The TG43 U1 update report recommends that accurate dose distribution data of the brachytherapysource in use should be obtained experimentally or by Monte Carlo (MC), to be used as input in the HDR Treatment Planning System (TPS). The purpose of this study is to obtain the dose rate distribution in liquid water media for the Flexisource HDR 192 Ir source (Isodose Control GmbH, Germany) using the Monte Carlo method to obtain the TG43 U1 parameters and the 2‐D rectangular dose rate table. Material and methods: The MC code GEANT4 (7.1 version) was used to estimate dose rate in …
Radiation transmission data for radionuclides and materials relevant to brachytherapy facility shielding
2008
To address the limited availability of radiation shielding data for brachytherapy as well as some disparity in existing data, Monte Carlo simulation was used to generate radiation transmission data for 60Co, 137CS, 198Au, 192Ir 169Yb, 170Tm, 131Cs, 125I, and 103pd photons through concrete, stainless steel, lead, as well as lead glass and baryte concrete. Results accounting for the oblique incidence of radiation to the barrier, spectral variation with barrier thickness, and broad beam conditions in a realistic geometry are compared to corresponding data in the literature in terms of the half value layer (HVL) and tenth value layer (TVL) indices. It is also shown that radiation shielding calc…
Broad-beam transmission data for new brachytherapy sources, Tm-170 and Yb-169
2005
The characteristics of the radionuclides (170)Tm and (169)Yb are highly interesting for their use as high dose-rate brachytherapy sources. The introduction of brachytherapy equipment containing these sources will lead to smaller required thicknesses of the materials used in radiation protection barriers compared with the use of conventional sources such as (192)Ir and (137)Cs. The purpose of this study is to determine the required thicknesses of protection material for the design of the protecting walls. Using the Monte Carlo method, transmission data were derived for broad-beam geometries through lead and concrete barriers, from which the first half value layer and tenth value layer are ob…
Verification of a commercial implementation of the Macro-Monte-Carlo electron dose calculation algorithm using the virtual accelerator approach.
2009
Abstract In this work, the accuracy of the implementation of the Macro Monte Carlo electron dose calculation algorithm into the radiation therapy treatment planning system Eclipse is evaluated. This implementation – called eMC – uses a particle source based on the Rotterdam Initial Phase-Space model. A three-dimensional comparison of eMC calculated dose to dose distributions resulting from full treatment head simulations with the Monte Carlo code package EGSnrc is performed using the ‘virtual accelerator’ approach. Calculated dose distributions are compared for a homogeneous tissue equivalent phantom and a water phantom with air and bone inhomogeneities. The performance of the eMC algorithm…
A Monte Carlo-aided design of a modular 241Am-Be neutron irradiator
2013
Monte Carlo studies aimed at designing a modular 241Am-Be neutron irradiator for testing neutron detectors and personal dosimeters and processing large volume samples are reported in this study. The evaluation of the shapes and thicknesses of the moderator and shielding materials was carried out by a MCNP5 Monte Carlo simulation code. The reliability of the simulation was experimentally verified by the activation of gold foils and TLD dosimeter measurements in an irradiation cell placed at the center of the test configuration.
SU-G-201-02: Application of RayStretch in Clinical Cases: A Calculation for Heterogeneity Corrections in LDR Permanent I-125 Prostate Brachytherapy
2016
Purpose: Tissue heterogeneities and calcifications have significant impact on the dosimetry of low energy brachytherapy (BT). RayStretch is an analytical algorithm developed in our institution to incorporate heterogeneity corrections in LDR prostate brachytherapy. The aim of this work is to study its application in clinical cases by comparing its predictions with the results obtained with TG-43 and Monte Carlo (MC) simulations. Methods: A clinical implant (71 I-125 seeds, 15 needles) from a real patient was considered. On this patient, different volumes with calcifications were considered. Its properties were evaluated in three ways by i) the Treatment planning system (TPS) (TG-43), ii) a M…
Towards clinical application of RayStretch for heterogeneity corrections in LDR permanent 125-I prostate brachytherapy
2017
Purpose RayStretch is a simple algorithm proposed for heterogeneity corrections in low-dose–rate brachytherapy. It is built on top of TG-43 consensus data, and it has been validated with Monte Carlo (MC) simulations. In this study, we take a real clinical prostate implant with 71 125I seeds as reference and we apply RayStretch to analyze its performance in worst-case scenarios. Methods and Materials To do so, we design two cases where large calcifications are located in the prostate lobules. RayStretch resilience under various calcification density values is also explored. Comparisons against MC calculations are performed. Results Dose–volume histogram–related parameters like prostate D90, …
Employment effects of reducing labour costs : considering potential bias in macro-estimates of the elasticity of labour demand
2017
In 2016 the Finnish government decided to implement the competitiveness pact in order to increase employment. The objective is to improve cost-competitiveness by lowering labor costs in the private sector. The elasticity of labour demand plays a key role in assessing the employment effects of the competitiveness pact. The idea of this study is based on the Economic Policy Council Report (2016) which argued that the government’s elasticity estimate is very high and predicts overly optimistic employment effects. The majority of studies estimate demand elasticities using aggregate data, which is likely to produce biased estimates. The problems relate in particular to the lack of exogenous vari…
Herramientas matemáticas para la valoración de la ampliación de una infraestructura portuaria
2003
infraestructura portuaria ya consolidada, que conlleva unas inversiones a largo plazo. Para ello hay que recurrir a medios de an´alisis capaces de recoger, en la medida de lo posible, la incertidumbre sobre la futura evoluci´on de los tr´aficos de mercanc´?as, sobre el efecto de la competencia entre puertos, etc., y que los m´etodos tradicionales no aproximan en toda su dimensi´on. Existe, adem´as, un problema de decisi´on de pol´?tica ´optima de gesti´on del proyecto que depende de variables de decisi´on que modelizan las opciones presentes en el mismo. Las oportunidades de inversi´on han sido tratadas como una colecci´on de opciones americanas sobre activos reales. Nosotros hemos optado p…