CARMEN CECILIA BUENO TOBIAS

CARMEN CECILIA BUENO TOBIAS

(Fonte: Lattes)

Resumo

Bacharel e Licenciada em Física pela PUC/SP (1978), tendo obtido nesta mesma Instituição os títulos de Mestre (1982) e Doutor (1987) em Ciências. Realizou pós-doutorado de curta duração no Depto. de Física da Universidade de Coimbra (1996) com bolsa FAPESP. Obteve também o título de Doutor (2004) em Tecnologia Nuclear pelo Instituto de Pesquisas Energéticas e Nucleares (IPEN). Durante o período 1979-2016 foi professora titular da PUC/SP. É pesquisadora titular no IPEN onde ingressou em 1995. Tem 30 anos de experiência na área de Engenharia Nuclear, com ênfase em Instrumentação para Medida e Controle de Radiação, atuando principalmente nos seguintes temas: detectores semicondutores de Si, espectrometria e dosimetria de partículas carregadas e radiação eletromagnética, detectores gasosos de catodo resistivo e parâmetros de transporte de elétrons em gases. (Texto extraído do Currículo Lattes em 08 out. 2021)

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Dosimetric parameters and radiation tolerance of epitaxial diodes for diagnostic radiology and computed tomography beams
2024 - GONCALVES, JOSEMARY A.C.; MANGIAROTTI, ALESSIO; ANTONIO, PATRICIA L.; CALDAS, LINDA V.E.; BUENO, CARMEN C.
A custom-made EPI diode-based dosimetry system is thoroughly characterized for diagnostic radiology and computed tomography beams. The diode has a thin n-type epitaxial layer (50 μm) grown on a thick (300 μm) Czochralski silicon substrate. It operates as an online radiation dosimeter in the short-circuit current mode. In this case, the key dosimetric quantity is the dose rate, correlated with the output current from the diode exposed to radiation. The corresponding collected charge (the integral of the current signal) is proportional to the dose. Irradiations are performed with the Pantak-Seifert 160HS Isovolt X-ray generator previously standardized by Radcal RC6-RD and RC3-CT ionization chambers. The data gathered with all radiation quality beams confirm the linearity with dose and dose rate despite a slight energy dependence. Independently from the beam energy, the dosimetric parameters of repeatability (<0.3%), long-term stability (0.4%/year), angular response (<3%, ± 5°), dose rate dependence (<3%), and signal-to-noise ratio (≥4900) fully adhere to the IEC 61674 recommendations. Compliance with the accumulated dose stability requirement (1.0%/40 Gy) is almost achieved with the pristine diode and effectively accomplished through radiation conditioning with 60Co gamma rays. Under the latter condition, the lifespan of the diode can easily reach 15 kGy, assuring the high reusability of this diode for diagnostic radiology and computed tomography dosimetry before requiring recalibrations.
Calibration coefficients of epitaxial diodes used in diagnostic radiology and computed tomography
2024 - GONCALVES, J.A.C.; ANTONIO, P.L.; CALDAS, L.V.E.; POTIENS, M.P.A.; BUENO, C.C.
Accumulated dose stability parameters in p-type and n-type silicon diodes
2024 - PASCOALINO, K.; GONCALVES, J.A.C.; CAMARGO, F.; TUOMINEN, E.; BUENO, C.C.
Characterization of a commercial PIN diode for radiotherapy photon beam dosimetry
2024 - SILVA, IANDRA T.; PIERI, KAREN; ALBINO, LUCAS D.; FONTANA, THIAGO S.; SANTOS, MATHEUS F. dos; ROESLER, ERNESTO; OLIVEIRA, CHARLES N.P.; ASFORA, VIVIANE K.; GONCALVES, JOSEMARY A.C.; KHOURY, HELEN J.; BUENO, CARMEN C.
The dosimetric characterization of a commercial diode (BPW-34) was performed using a True Beam accelerator (Varian), with flattening filter (FF) photon beams of 6 and 15 MV and flattening filter free (FFF) of 6 MVFFF. The main performance characteristics, namely dose response, energy and dose rate dependence, field output factor, and percentage depth dose profile (PDD), were compared with those available in the literature and, whenever possible, benchmarked against the Varian Eclipse treatment planning system (TPS) predictions. Regardless of the energy, the results showed that the dose response curves are linear (R2 = 1) with nonlinearity parameters less than 0.1% and 0.3% of repeatability. Furthermore, the average dose rate effect (0.7%) is almost negligible within the range of 20–600 MU/min (6 MV, 15 MV) and 400–1400 MU/min (6 MVFFF). Despite these good results, the charge sensitivity measurements evidenced that the diode response depends slightly on the energy, being within 5% for 6 MV–15 MV. It is important to underline that all these results adhere to the standard radiotherapy dosimetry protocols. Moreover, the general output field factor measurements and the percentage depth dose profiles, which are in excellent agreement with the Eclipse TPS calculations, also demonstrated that the diode BPW-34 is a low-budget alternative radiotherapy photon beam dosimeter.
Online electron beam monitoring with a diode-based dosimetry system in routine quality control
2023 - GONCALVES, JOSEMARY A.C.; MANGIAROTTI, ALESSIO; SOMESSARI, ELIZABETH S.R.; NAPOLITANO, CELIA M.; BUENO, CARMEN C.
Dosimetric parameters and radiation tolerance of epitaxial diodes for diagnostic radiology and computed tomography X-rays
2023 - GONCALVES, JOSEMARY A.C.; MANGIAROTTI, ALESSIO; POTIENS, MARIA P.A.; CALDAS, LINDA V.E.; BUENO, CARMEN C.
Characterization of a commercial PIN diode for radiotherapy photon beam dosimetry
2023 - SILVA, IANDRA T.; PIERI, KAREN; ALBINO, LUCAS D.; FONTANA, THIAGO S.; SANTOS, MATHEUS F. dos; ROESLER, ERNESTO; ASFORA, VIVIANE K.; OLIVEIRA, CHARLES; GONCALVES, JOSEMARY A.C.; BUENO, CARMEN C.; KHOURY, HELEN J.
Dosimetric evaluation of an epitaxial silicon diode as an online dosimeter for orthovoltage photon beam radiotherapy
2021 - BUENO, C.C.; GONCALVES, J.A.C.; MANGIAROTTI, A.
The response of a dosimetry system based on an epitaxial silicon diode as an online dosimeter for orthovoltage photon beam radiotherapy has been investigated in this work. To be used as a dosimeter, each diode is housed in a light-tight probe, and its readout electrode is directly connected to the Keithley 6517B electrometer. All current measurements are carried out in short-circuit mode with the diode unbiased and its backplane grounded. The data acquired by the electrometer are directly sent to a personal computer via a GBIP interface controlled by software developed in LabView to analyze the current signals. A Pantak/Seifert X-ray tube is used to irradiate the diode, placed 50.0 cm away in a radiation field of 8 cm, with 10, 25, 30, and 50 kV photons. The dose rate response is investigated for the 50 kV beam by varying the current tube from 2 to 20 mA. As expected, the induced current is linearly dependent on the dose rate within the range of 0.8 and 8.05 mGy/s. The current signals are quite stable, with a repeatability parameter of less than 0.2%. The dose-responses assessed offline by integrating the current signals are linear between 0.5 and 3.0 Gy despite being slightly dependent on the photon energy. However, in this dose range, no dose rate dependence is observed. These results are theoretically supported by dose and dose rate calculations performed assuming the diode is thin compared with the standard values of the minority carrier diffusion lengths in the epitaxial layer. Good agreement is found between calculations and experimental data. Investigations of possible radiation damage produced in the diode through dynamic measurements of dark current and capacitance as a function of the accumulated dose are currently in progress.
Dose rate mapping in an industrial 60Co irradiator using an online photodiode-based dosimetry system
2021 - GONCALVES, J.A.C.; MANGIAROTTI, A.; BUENO, C.C.
In the radiation processing field, any irradiation process is designed to irradiate products uniformly, but in practice, a reasonable variation in the absorbed dose through the product is accepted. However, the irradiation of inhomogeneous or irregularly shaped products gives rise to complex dose variations only assessed through dose mapping. It requires complementary dosimeters bearing good spatial resolution, prompt and easy readout, and cost-effectiveness. These features are found in silicon diodes that, despite all these advantages, are prone to radiation damage. This damage is mitigated with photodiodes whose thicknesses are much smaller than the minority carrier diffusion length at the anticipated accumulated dose. In this work, an in-house dosimetry system based on a thin photodiode is applied for online mapping dose rates, between 3.7 and 52.8 Gy/h, delivered by a Panoramic 60Co industrial facility. The operational principle of these dosimeters relies on the real-time acquisition of the induced currents from the irradiated diode operating in the short-circuit mode without externally applied voltage. Under this condition, the dose is assessed offline via the integration of these current signals. The radial mapping of the radiation field is performed by rotating the diode around the central axis of the panoramic irradiator, covering 360º at intervals of 10º. For comparative purposes, alanine dosimeters are also irradiated together with the diode. The experimental results are benchmarked with Monte Carlo simulations of the dose rate curves. Good agreement between the simulated values and the readings of both dosimeters is found. It reveals that the photodiode-dosimetry system is a reliable alternative to map dose rate fields and the effectiveness of Monte Carlo simulations as a predictive tool for dose rate measurements in an irradiator.
Measurement of the insensitive surface layer thickness of a PIN photodiode based on alpha-particle spectrometry
2022 - PASCOALINO, K.; CAMARGO, F.; GONCALVES, J.A.C.; BUENO, C.C.
In this work, the insensitive layer thickness of a PIN photodiode (SFH206K - Osram) has been measured by varying the incident angle of a collimated monoenergetic alpha particle beam. This technique is based on variations in the path lengths of alpha particles through the insensitive layer and the correspondent energy losses when they impinge on a diode surface at different angles. Therefore, the pulse heights of these alpha particles, closely related to the energies deposited in the active volume of the diode, also depend on their incident angle. So, the difference between the pulse height of alpha particles perpendicularly incident on the diode surface and at any incident angle enables the insensitive layer thickness to be assessed. The result obtained (711  23) nm, less than 1% of the intrinsic layer thickness, besides validating the employed method, demonstrates that the investigated diode is suitable for high resolution charged particle spectrometry.