PAULO DE TARSO DALLEDONE SIQUEIRA

PAULO DE TARSO DALLEDONE SIQUEIRA

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Influence dosimetric study of different couches in radiotherapy treatments
2022 - DEL NERO, R.A.; EMILIOZZI, C.Z.S.; SIQUEIRA, P.T.D.; ANTUNES, P.C.G.; SERANTE, A.R.
Radiotherapy is a recommended procedure for 52% of cancer cases, in average, as one of the treatment forms, therefore, it is important for the clinical practice to investigate the affecting factors in dose distribution received by the patients, such as immobilization devices and treatment couch. With the introduction of treatments with modulated intensity techniques like IMRT and VMAT, the number of incidence fields used for patient treatment increased, making couch’s dosimetric effect more significant in these modalities. The attenuation data acquisition referring to the treatment couches, as well as the TPS data evaluation, show important parameters for the clinical practice because they influence what happens with the dose delivery during the treatment, ensuring a better quality and safety to the treatments. This research presents experimental results evaluating the couch’s impact in the treatments by a study of perturbation in the distribution of surface dose, and dose attenuation according to the gantry’s angle for the couches BrainLABTM, ExactTM and iBEAMTM. Then we propose better density values for the couches BrainLABTM and ExactTM for their inclusion in EclipseTM TPS. Lastly, we compare the dose difference considering the presence or not of couch in the planning. In conclusion, the beam’s attenuation increase by the couches and the doses alterations on the skin must be taken in consideration in the treatment planning process. It is of great relevance that each treatment center perform internal tests to determinate the best density values for available TPS.
Computational model of a 3D dosimetry system - ArcCHECK®
2019 - MAZER, A.C.; NAKANDAKARI, M.V.N.; RIBEIRO, V.A.B.; SIQUEIRA, P.T.D.; SHORTO, J.M.B.; YORIYAZ, H.
Ionizing radiation therapies have been improving over the years, becoming more specific for each patient. Thereby, as the treatment planning system (TPS) complexities increases, the quality assurance (QA) methods have to be in constant evolution. One of the techniques that demand great complexity is the Volumetric Modulated Arc Therapy (VMAT), and one possible way to VMAT commissioning is using 3D dosimetry systems. Recently a new 3D dosimetry system called ArcCHECK had been developed and commercialized mainly for VMAT quality assurance. It is water-equivalent and composed by an array of 1386 diodes arranged in a helical pattern. Since simulation methods, like Monte Carlo method, ensure highly accurate results, MCNP (A General Monte Carlo N-Particle Transport Code System) is totally reliable for problems that involve radiation transport. This work presents two computational models for Monte Carlo simulations to predict detection responses in the QA procedure using the ArcCHECK. The computational models were validated comparing the system responses obtained from MCNP6 simulations against measured responses due to a 6 MeV clinical photon beam from a Linear Accelerator. 2D dose maps were reported here with good agreement between simulated and measured values.
Verification of angular dependence in MOSFET detector
2019 - SOUZA, C.H.; SHORTO, J.M.B.; SIQUEIRA, P.T.D.; NUNES, M.G.; SILVA JUNIOR, I.A.; YORIYAZ, H.
In vivo dosimetry is an essential tool for quality assurance programs, being a procedure commonly performed with thermoluminescent dosimeters (TLDs) or diodes. However, a type of dosimeter that has increasing popularity in recent years is the metal-oxide-semiconductor field effect transistor (MOSFET) detector. MOSFET dosimeters fulfill all the necessary characteristics to realize in vivo dosimetry since it has a small size, good precision and feasibility of meas-urement, as well as easy handling. Nevertheless, its true differential is to allow reading of dose in real time, enabling immediate intervention in the correction of physical parameters deviations and anticipation of small anatomical changes in the patient during treatment. In order for MOSFET dosimeter to be better accepted in clinical routine, information reporting performance should be available frequently. For this reason, this work proposes to verify reproducibility and angular dependence of a standard sensitivity MOSFET dosimeter (TN-502RD-H) for Cs-137 and Co-60 sources. Exper-imental data were satisfactory and MOSFET dosimeter presented a reproducibility of 3.3% and 2.7% (±1 SD) for Cs-137 and Co-60 sources, respectively. In addition, an angular dependence of up to 6.1% and 16.3% for both radioactive sources, respectively. It is conclusive that MOSFET dosimeter TN-502RD-H has satisfactory reproducibility and a considerable angular dependence, mainly for the Co-60 source. This means that although precise measurements, special attention must be taken for applications in certain anatomical regions in a patient.
Comparação entre duas metodologias para correção da uniformidade de fontes extensas de referência
2017 - SILVA JUNIOR, I.A.; SIQUEIRA, P.T.D.; NASCIMENTO, E.; VIVOLO, V.; POTIENS, M.P.A.
São apresentados neste artigo os procedimentos para obtenção de fatores de correção de uniformidade de fontes ex- tensas de referência sugerida por duas metodologias distintas. A primeira metodologia é apresentada pelo Guia de Boas Práticas do Nº 14 do NPL, que oferece uma correção numérica e a segunda é uma correção que utiliza o código de transporte de radiação, MCNP5. Ambos os métodos resultam na proposição de valores de correções muito simila- res percentualmente, com desvio máximo de 0,24%.