Aplicabilidade e validação do Geant4 para fótons e elétrons em radioterapia / GEANT4 applicability and validation to Photons and Electrons in Radiotherapy

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

14/06/2011

RESUMO

Due to the increasing use of ionizing radiation in medical applications, in recent decades, the simulation codes for radiation interacting with matter, based on Monte Carlo Method, have been constantly adapted to applications in medical physics. TheMonte Carlo method is a statisticalmethod of numerical simulation of problems using essentially a sequence of random numbers. Currently, the method can be applied in physical, mathematical and biological simulations, the behavior of systems is described by random sampling of probability density functions and accumulation of the observed values of the samples producing the final result of the simulation. In the case of radiation transport, the expected value of quantities of interest such as, for example, dose or energy deposited in a medium or interest volume simulated, can be estimated. In most applications of the method, the physical process is simulated directly, requiring only the mathematical description of the physical process, ie the probability density function. Among the most commonly used codes for radiation transport are: the EGS (Electron Gamma Shower), MCNP (Monte Carlo Neutron Photon Transport Code), ITS (Integrated Tiger Series), PENELOPE (Penetration and Energy Loss of Electrons and Positrons) and Geant4 (Geometry and Tracking) released by CERN (European Organization for Nuclear Research). The GEANT4 is a set of computational tools (toolkit) that uses object-oriented programming in C++, created through an international project and initially used for applications in high energy physics, but is now used in areas that include from astrophysics to medical physics, with energies of 250 eV to 100 TeV. In the GEANT4 toolkit have been incorporated several physical processes and particles that allow its use in medical physics. This code has several advantages over other codes, for example, dealing with all types of particles and complex geometries and to be in C++. With the increasing use of Monte Carlo codes and the various applications of GEANT4 in medical physics, published recently, this code is presented as a promising tool for applications in radiotherapy, which have been used in various types of simulations. Considering the advantages of this code and its applications in medical physics in this dissertation, it was developed various simulations to verify the GEANT4 applicability and validation for radiotherapy applications. For example, it was study various aspects of implementation of the code, for example, the dependence of the energy deposited with non-physical parameters of the electrons transport algorithm, the transport of electrons to energies 1 to 20 MeV, in which GEANT4 and various other codes, presented problems of great relevance, and the influence of number of events in the simulated results. Also, it was evaluated the application of G4 in the transport of radiation through simulations of photons and electrons emitted by equipment and sources used in radiotherapy, as linear accelerator and sources of Co-60 and Ir-192, and by calculation of some quantities such as dose range and Stopping Power of monoenergetic electrons transported in water. The results in all simulations developed present a accuracy within 2%, indicating that Geant4 can be used, in simulations of photons and electrons, for applications in radiotherapy

ASSUNTO(S)

método de monte carlo fótons elétrons radioterapia monte carlo method photons electrons radiotherapy

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