PAULO DE TARSO DALLEDONE SIQUEIRA
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Artigo IPEN-doc 27119 Variability2020 - SILVA JÚNIOR, IREMAR A. da; SIQUEIRA, PAULO de T.D.; NASCIMENTO, EDUARDO do; YORIYAZ, HELIO; SORDI, GIAN-MARIA A.A.; POTIENS, MARIA da P.A.In this paper we present the impact of variability, a surface source parameter, on the efficiency evaluation of surface contamination monitors. This study was based on two source uniformity correction methodologies and data from real surface source distributions. Surface source intensity distribution has been changed by rearranging the cells (portions of the active area of each LARS) while keeping the same source uniformity value. Instrument efficiencies have been calculated for different sets of uniformities and variabilities. This study led to emphasize the importance of variability, a differential source intensity distribution parameter, over the uniformity, an integral source intensity distribution parameter, and reinforced the importance of the source uniformity correction procedure on the course of surface contamination monitor calibration.Artigo IPEN-doc 27117 Correction factors for non-uniform large-area reference sources2020 - SILVA JÚNIOR, IREMAR A.; SIQUEIRA, PAULO de T.D.; NASCIMENTO, EDUARDO do; YORIYAZ, HELIO; SORDI, GIAN-MARIA A.A.; VIVOLO, VITOR; POTIENS, MARIA da P.A.Based on uniformity measurements of large-area reference sources used in calibration procedures of surface contamination monitors, an investigation was carried out to obtain a method that estimates the bias originated from surface source intensity distribution deviation from the ideal uniform distribution and corrects it. It relies on correcting the estimated instrument efficiency by applying correction factors driven from the uniformity distribution profiles of the sources used in calibration procedure. Simulations of the monitor calibration procedure are run for 2 distinct surface source distributions: the real and the ideally uniform distributions. Correction factors are driven from counting rate estimates obtained from each source representation. In order to evaluate adequacy of this proposition it was validated against a method proposed by the NPL in the Good Practices Guide No.14.Artigo IPEN-doc 24053 Verification of angular dependence in mosfet detector2017 - SOUZA, CLAYTON H.; SHORTO, JULIAN M.B.; SIQUEIRA, PAULO T.D.; NUNES, MAIRA G.; SILVA JUNIOR, IREMAR A.; YORIYAZ, HELIOIn 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 measurement, as well as easy handling. Nevertheless, its true differential is to allow reading of the dose in real time, enabling immediate intervention in the correction of physical parameters deviations and anticipation of small anatomical changes in a 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. Experimental 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.Artigo IPEN-doc 21093 Overcoming the reference large-area sources non-uniformity in surface area monitor calibration2015 - SILVA JUNIOR, IREMAR A.; SIQUEIRA, PAULO de T.D.; XAVIER, MARCOS; NASCIMENTO, EDUARDO do; POTIENS, MARIA da P.A.