RESUMO
In the frame of the EU Coordination Action CONRAD (coordinated network for radiation dosimetry), WP4 was dedicated to work on computational dosimetry with an action entitled 'Uncertainty assessment in computational dosimetry: an intercomparison of approaches'. Participants attempted one or more of eight problems. This paper presents the results from problems 4-8-dealing with the overall uncertainty budget estimate; a short overview of each problem is presented together with a discussion of the most significant results and conclusions. The scope of the problems discussed here are: the study of a (137)Cs calibration irradiator; the manganese bath technique; the iron sphere experiment using neutron time-of-flight technique; the energy response of a RADFET detector and finally the sensitivity and uncertainty analysis for the recoil-proton telescope discussed in the companion paper.
Assuntos
Elétrons , Nêutrons , Fótons , Dosagem Radioterapêutica , Radioterapia Assistida por Computador , Incerteza , Algoritmos , Radioisótopos de Césio/química , Humanos , Manganês/química , Radiometria/instrumentação , Radioterapia Assistida por Computador/instrumentaçãoRESUMO
OEDIPE (a French acronym standing for 'Tool for Personalized Internal Dose Assessment'), developed by IRSN, is used to perform virtual calibration of a real in vivo counting system. The system, installed recently at Le Vésinet, consists of four Broad Energy germanium detectors. CT images of Livermore torso phantom are used to create a voxel phantom after segmentation using Dosigray software. Virtual calibration using the voxel phantom was validated by the comparison of peak efficiencies between Monte Carlo calculation and phantom experiments using lung sources 152Eu and 241Am at different chest wall thickness (CWT = 19, 25, 30, 43 mm). The comparison between virtual calibration and physical phantom experiments shows that the relative deviations are within +/- 10% in the energy range of 59.5-1408 keV, and within +/- 30% for 17.5 keV photons.
Assuntos
Algoritmos , Modelos Biológicos , Software , Contagem Corporal Total/métodos , Contagem Corporal Total/normas , Calibragem , China , Simulação por Computador , Método de Monte Carlo , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Contagem Corporal Total/instrumentaçãoRESUMO
BACKGROUND: 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 to a real medical linear accelerator and to one homogeneous and four heterogeneous dosimetric phantoms. AIMS: The aim of this exercise was to identify, by comparison of different MC models with a complete experimental dataset, critical aspects useful for MC users to build and calibrate a simulation and perform a dosimetric analysis. RESULTS: Results show on average a good agreement between simulated and experimental data. However, some significant differences have been observed especially in presence of heterogeneities. Moreover, the results are critically dependent on the different choices of the initial electron source parameters. CONCLUSIONS: This intercomparison allowed the participants to identify some critical issues in MC modelling of a medical linear accelerator. Therefore, the complete experimental dataset assembled for this intercomparison will be available to all the MC users, thus providing them an opportunity to build and calibrate a model for a real medical linear accelerator.