PATRICIA BERINGHS RIO

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Radiosurgery dosimetry using CaSO4:Eu OSLD film
2023 - GASPARIAN, PATRICIA B.R.; MALTHEZ, ANNA L.M.C.; TORQUATO, MICHELE; CAMPOS, LETICIA L.
Recent studies demonstrated that optically stimulated luminescence (OSL) systems allow the evaluation of doses for 2D mapping in a relatively fast and simple way and results show submillimeter resolution. This work presents, for the first time, an optically stimulated luminescence dosemeter (OSLD) in the form of film made with CaSO4:Eu particles embedded in a silicone elastomer matrix. The OSLD film was produced using a low-cost and relatively simple methodology. This film is reusable and the signal can be satisfactorily bleached using blue LEDs. The main dosimetric properties were evaluated using TL/OSL Risø reader with blue stimulation and Hoya U-340 filter. Investigation shows repeatability within 3% when measuring with the same film sample. Regarding the OSLD film homogeneity, nearly 12% sensitivity change was observed within the 5 × 5 cm2 produced film. Additionally, the dose response curve shows linearity from 5 to 25 Gy. Fading of the OSL signal is relatively high, about 50% in the first week and then is stable. Nevertheless, a 3 × 3 cm2 OSLD film was successfully used to map dose distribution in radiosurgery (6 MV photon beam). This work demonstrates the feasibility of 2D dosimetry using reusable OSLD films based on CaSO4:Eu.
Study of radioluminescence from CaSO4:Eu films for real-time dosimetry
2023 - GASPARIAN, PATRICIA B.R.; MALTHEZ, ANNA L.M.C.; CAMPOS, LETICIA L.; TRINDADE, NEILO M.; OLIVEIRA, ALDO R. de; MARTINS, ROBERTO T.E.K.
Active detectors based on semiconductors and diodes are largely applied for clinical dosimetry, however they present limitations mainly related to complex electronic structure, limited spatial resolution and high cost. Several materials which exhibit thermoluminescence (TL) and optically stimulated luminescence (OSL) also present radioluminescence (RL), as Al2O3:C,Mg. In principle, RL materials can be used in real-time dosimetry as active detectors if the intensity of the RL signal can be associated with the absorbed dose. The sensitive material can be coupled to optical fibers, CCD devices, or other device to collect its light emission. The phosphor CaSO4:Eu has been studied as TL and OSL detector and literature reports good reproducibility, linear dose-response and negligible fading. Previously, CaSO4:Eu OSL films were produced and applied for two-dimensional dose mapping in radiotherapy. Considering the potential application of CaSO4:Eu films for medical applications, in this work we studied the RL emission of CaSO4:Eu films. Firstly we used a Horiba Absorbance and Fluorescence Spectrometer, model Duetta, and obtained the emission spectra of the CaSO4:Eu films, exciting with different wavelenghts and observed two emission centre groups. The first group is at 385 nm, related to Eu2+ and the second group, related to Eu3+ is at 580 nm, 600 nm and 700 nm. Secondly, to study the RL emission from the CaSO4:Eu film, we used a custom made equipment named LUMI22, which has an X-ray tube (Moxtek 50kV) powered and controlled by a standard controller (FTC-200) to irradiate the samples, and a miniature fiber optic spectrometer (Ocean Optics, FLAME-S-XR1-ES) that is used to identify the wavelength of the emitted light (range 200-1050 nm). Results showed a radioluminescent peak at 390 nm, which should be related to Eu2+. The RL sensitivity is (46.1 ± 1.3) 103 counts/Gy. The film does not need thermal or optical treatment and the radioluminescent peak is reproducible. Comparing the RL intensity after 10 consecutive irradiations with the same conditions, the maximum coeficient of variation is 2.5%. The dose response of the RL is linear (R-square 0.9959) from 0.04 to 0.3 Gy. Results show that the CaSO4:Eu film is promissing for use with the RL technique in real-time clinical dosimetry. It should be possible to evaluate dose distributions in real time using the film and a reader with several fiber optics, for example.
An overview study on the TL and OSL dosimetry patent processes over time
2023 - GASPARIAN, P.B.R.; MALTHEZ, A.L.M.C.; MARIANO, L.; CAMPOS, L.L.; POLITANO, R.
Since its discovery, ionizing radiation has been used in many different applications. Materials and methods have been developed to measure and quantify radiation doses. Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) are two techniques used for radiation dosimetry. Both TL and OSL are primarily applied in several areas, such as dating of ancient materials, equipment quality control and individual monitoring. One of the parameters to measure the knowledge and development of a technology is the number of patents related to the field. In this work, we established a methodology for patent search on the World Intellectual Property Organization (WIPO) database aiming to review the development of TL and OSL dosimetry over time. We concluded that along with the OSL technique development, the TL technique should continue to be explored in radiation dosimetry.
Performance test of a matrix for radiation detector OSL films
2022 - GASPARIAN, PATRICIA B.R.; MALTHEZ, ANNA L.M.C.; BICALHO, DANIEL B.; CAMPO, ALEXANDRE B.; CAMPOS, LETICIA L.
Radiosurgery dosimetry using OSL film made with CaSO4:Eu
2022 - GASPARIAN, PATRICIA B.R.; MALTHEZ, ANNA L.M.C.; TORQUATO, MICHELE; CAMPOS, LETICIA L.
Recent studies demonstrated that optically stimulated luminescence (OSL) systems allow the evaluation of doses for 2D mapping in a relatively fast and simple way and results show submillimeter resolution (Ahmed et al., 2017; Jahn et al., 2013). The two most advanced-stage studies with satisfactory application in 2D dose mapping are based on commercial prototype detectors (Al2O3:C and BeO). Some OSL materials have been evaluated in research laboratories for use in 1D and 2D dose distribution assessments and there is no common sense on the best OSL material for each application (Yukihara and Kron, 2020). This work presents, for the first time, an optically stimulated luminescence (OSL) film made with CaSO4:Eu particles embedded in a silicone elastomer matrix. The OSL film was produced using a low-cost and relatively simple methodology. This film is reusable and the signal can be satisfactorily bleached using blue LEDs. The main dosimetric properties were evaluated using TL/OSL Risoe reader with blue stimulation and Hoya U-340 filter. Investigation shows repeatability within 5% when measuring with the same film sample. Regarding the OSL film homogeneity, nearly 15% sensitivity change was observed within the 5 x 5 cm2 produced film. Additionally, the dose response curve shows linearity from 5 to 25 Gy. Further studies are necessary to understand and minimize the influence of OSL signal fading, which seems as high as 70% in the first week and then is stable. Nevertheless, a 3 x 3 cm2 OSL film was successfully used to map dose distribution in radiosurgery (6 MeV photon beam). This work demonstrates the feasibility of 2D dosimetry using low-cost and reusable OSL films based on CaSO4:Eu.
Using the optically stimulated luminescence technique for one- and two-dimensional dose mapping
2022 - GASPARIAN, PATRICIA B.R.; MALTHEZ, ANNA L.M.C.; CAMPOS, LETICIA L.
In respect of radiation dosimetry, several applications require dose distribution verification rather than absolute dosimetry. Most protocols use radiological and radiochromic films and ionization chambers or diode arrays for dose mapping. The films are disposable which causes the precision of the results dependent on film production variability. The measurements with arrays of ionization chambers or diodes mainly lack spatial resolution. This review aims to provide an overview of the use of optically stimulated luminescence detectors (OSLDs) for one-dimensional (1D) and two-dimensional (2D) dose mapping in different applications. It reviews the ideas, OSL materials, and applications related to the assessment of dose distribution using OSLDs in the form of film or ceramic plate (BeO). Additionally, it reviews research published in the international scientific literature from 1998 to 2021. As an outcome, a table containing the main characteristics of each relevant paper is shown. The results section was divided by the type of OSL material, and we briefly described the principal findings and the significant developments of each mentioned study such as film production and OSL reader assembly. The purpose of this study was to present an overview of the main findings of several research groups on the use of OSLD in the form of film or plate for 1D and 2D dose mapping. Finally, the potential future development of dose mapping using OSLD films was outlined.
Desenvolvimento, produção e caracterização de filmes OSLD baseados em CaSO4 para aplicação em dosimetria das radiações
2022 - GASPARIAN, PATRICIA B.R.
Nos tratamentos modernos de radioterapia (RT), campos pequenos e distribuições de dose complexas requerem técnicas de dosimetria adequadas e precisas. Filmes radiocrômicos e arranjos de câmaras de ionização (CI) apresentam limitações, como alto custo, precisão dependente da variabilidade de produção dos filmes e resolução limitada (arranjo de CI). Estudos recentes demonstraram que sistemas de luminescência opticamente estimulada (do inglês optically stimulated luminescence -OSL) permitem a avaliação de doses para mapeamento 2D de forma relativamente rápida e simples e os resultados mostram resolução submilimétrica. Este trabalho apresenta, pela primeira vez, um dosímetro de luminescência opticamente estimulada (OSLD) na forma de um filme flexível feito com partículas de CaSO4:Eu embebidas em uma matriz de elastômero de silicone. O filme OSLD foi produzido por uma metodologia relativamente simples e de baixo custo. Esse filme é reutilizável e o sinal pode ser limpo satisfatoriamente com uso de LEDs azuis. As principais propriedades dosimétricas foram avaliadas utilizando o leitor TL/OSL Risø com estimulação azul e filtro Hoya U-340. A investigação mostra repetibilidade dentro de 3% ao medir com a mesma amostra de filme. Em relação à homogeneidade do filme OSLD, foi observada uma mudança de sensibilidade de aproximadamente 12% ao longo do filme OSLD de 5 x 5 cm2. Além disso, a curva de resposta em função da dose mostra linearidade de 5 a 25 Gy. O desvanecimento do sinal OSL é relativamente alto, cerca de 50% nas primeiras 48h, e depois fica estável. Um filme OSLD de 3 x 3 cm2 foi usado com sucesso para mapear a distribuição de dose em radiocirurgia (feixe de fótons de 6 MV). Este trabalho demonstra a viabilidade da dosimetria 2D usando filmes OSLD reutilizáveis baseados em CaSO4:Eu.
Study of the dosimetric properties of CaSO4:Dy using OSL technique
2022 - GASPARIAN, P.B.R.; MALTHEZ, A.L.M.C.; YOSHIMURA, E.M.; UMISEDO, N.K.; CAMPOS, L.L.
Calcium sulfate doped with dysprosium (CaSO4:Dy) has been used for personal dosimetry using the thermoluminescence (TL) technique for decades and its TL properties are well-known. Considering the advantages of the OSL technique (relatively simple and faster readout and detector reusability) and the potential application of CaSO4:Dy as an OSL detector, this study aimed to investigate the dosimetric properties of CaSO4:Dy using the OSL technique. The present study was carried out using CaSO4:Dy pellets prepared at IPEN irradiated and read in a TL/OSL Risø reader with blue light stimulation and Hoya U-340 filter. OSL dosimetric properties essentially dose response, reproducibility, and fading characteristics were evaluated. Moreover, TL and OSL signals were compared to study the correlation between OSL signals and TL peaks. CaSO4:Dy OSL response is linear from 0.1 to 10 Gy and shows reproducibility better than 5%. The low-temperature TL peak is unstable; however, the OSL signal seems to be associated with higher-temperature peaks.
Study of the dosimetric properties of CaSO4:Dy using OSL technique
2018 - GASPARIAN, P.B.R.; YOSHIMURA, E.M.; UMISEDO, N.K.; CAMPOS, L.L.; MALTHEZ, A.L.M.C.
Avaliacao de folhas de chumbo utilizadas para determinacao da equivalencia em atenuacao de dispositivos usados em radioprotecao
2004 - SALVADOR, F.C.; RIO, P.B.; NERSISSIAN, D.Y.; COSTA, P.R.; CALDAS, L.V.E.