Avaliação dosimétrica do acelerador linear modelo Synergy visando a implementação da técnica VMAT

Abstract

In recent decades radiotherapy lived with a great technological evolution, not only in equipment but also in treatment techniques.The rotational intensity modulated technique also known as VMAT is even more complex when compared to IMRT due to their higher number of degrees of freedom, such as gantry rotation and dose rate.Despite few centers have VMAT as a treatment option, this technique is already a reality in Brazil and its clinical implementation requires a rigorous quality control program. Aiming to ensure that the linear accelerator, using this technique, delivered the correct dose to the patient, in this work a dosimetric study was performed to implement this technique. The work was adapted by TG119 and divided into three parts. It was assumed that all mechanical tests had already been performed, so the End to End tests were performed for dosimetricverification.In the first step a solid water plates phantom with two ionization chambers was used to measure dose in the low and high gradient region.In the second step the main TG119 tests were adapted for the VMAT technique and performed following the TG119 recommendations. In the third step a phantom with heterogeneity was used in order to force a more complex fluencemap.In all tests satisfactory results were found, since the objectives planes until the planning quality controls and the point dose comparison with the ionization chamber.Theplannings were evaluated by the Gamma evaluation method and approved following the criteria proposed by TG119 and TG128, were all points has an approval beyond 95% as the previous documents named recommend.The dose comparisons between the TPS and the ionization chamber had smaller differences than 3% suggested by TG119.So it can be concluded that the dose delivered to the patient will be performed in a correct way under the established limits.