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Resumo IPEN-doc 31032 Thermoluminescence and Optically Stimulated Luminescence of CaSO4:Mn,Tb with different dopant concentrations
2024 - SILVA, A.M.B.; SOUZA, D.N.; CALDAS, L.V.E.
This study systematically evaluates the thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of CaSO4 crystals doped with manganese (Mn) and terbium (Tb), focusing on dopant concentrations within the ranges of Mn (0.1 mol% – 2 mol%) and Tb (0.05 mol% – 1 mol%). Synthesized via the slow evaporation route, this investigation is part of an ongoing experimental series initiated by Silva et al. (2022) [1], exploring CaSO4:Mn,Tb crystals at a concentration of 0.1 mol%, the validating their properties for dosimetric purposes. A structural phase identification was conducted using X-ray diffraction, and emission and excitation photoluminescence (PL) spectra confirmed the presence of Tb3+ and Mn2+ ions in the crystalline matrices. Dosimetric characterization utilized pellets prepared by incorporating Teflon into the phosphors. In-depth investigations involved analyzing TL glow curves and Continuous Wave Optically Stimulated Luminescence (CW-OSL) curves. Observations revealed that TL intensity increased as the co-doped concentration of Tb decreased while maintaining the concentration of Mn constant. Conversely, at a constant terbium concentration, TL intensity was higher with 0.5 mol% of manganese compared to 0.1 mol%, but higher concentrations of manganese (1 mol% and 2 mol%) resulted in decreased TL intensity. The study also explored dose-response, reproducibility, fading, sensitivity, step-annealing curve analyses, experimental determination of temperature dependence, and the minimum detectable dose (MDD) exposed to beta radiation of the pellets. This research underscores the importance of optimizing dopant concentrations to enhance the potential of these phosphors for precise and reliable dosimetry, thereby advancing both the understanding of these materials and their potential for further development in the field of radiation dosimetry.
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Resumo IPEN-doc 31031 Performance evaluation of a new dosimetric system for lens dosimetry made using 3D printing
2024 - NASCIMENTO, G.G.; RODRIGUES JUNIOR, O.; SAVI, M.; VILLANI, D.; POTIENS, M.P.A.
Technology advances in the health sector make it possible for medical radiology services, especially interventional radiology, to be more requested by doctors, which results in a significant increase in the number of procedures performed and the number of patients and occupationally exposed individuals (OEI) [1]. This increase in exposure of OEIs has caused concern regarding the exposure of the lens to ionizing radiation, since this tissue is considered a tissue with high radiosensitivity. This concern about exposing the lens region to ionizing radiation has existed for more than 10 years [2], considering these concerns, in 1950 the International Commission on Radiological Protection (ICRP) listed the lens of the eye as a critical organ [3]. In 2011, ICRP recommended a reduction in the occupational dose limit for the lens region from 150 mSv/year to 20 mSv/year [4]. In addition to technology advances and optimization of procedures used to reduce doses and risks that may affect the patient in interventional radiology applications, it is necessary to have a monitoring system suitable for the occupation. This monitoring is carried out using a dosimeter, which is part of a dosimetric system composed of a dosimeter holder, detector and a reading system compatible with the detector. In this work, chip-shaped LiF:Mg,Ti thermoluminescent detectors, commercially known as TLD-100, were used. For this study, a dosimeter holder produced in 3D printing was developed for use in eye lens dosimetry. A Raise 3D printer model Pro2 was used, which works using the FFF technique, the dosimeter holders were made from PLA and ABS material. The dosimeter holder has space to accommodate up to two chip-shaped detectors and has a support that fits with the glasses stem. The irradiations were carried out using Pantak/Seifert X-ray equipment, model Isovolt 60 HS. The N-100 radioprotection quality was used, with an energy of 83 keV, within the energy range between 40 and 120 keV, the quality used is within the range used in interventional radiology. The tests were conducted in accordance with the recommendations of ISO 12794:2000 [5]. From a dosimetric point of view, the type of material used to manufacture the dosimeter holders did not present significant differences. However, dosimeter holders made of PLA showed better resistance during the procedures.
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Resumo IPEN-doc 31030 Operational and Dosimetric Parameters of a 1.5 MeV electron beam irradiator in static and dynamic irradiation modes
2024 - GONÇALVES, J.A.C.; ASFORA, V.K.; KHOURY, H.J.; BUENO, C.C.
Electron beam (EB) accelerators have been increasingly used in radiation processing applications. Most aim to achieve reproducible chemical and biological effects on the irradiated material to preserve or modify its characteristics with tight control of the absorbed dose (10-100 kGy). Accurate dosimetry, mainly carried out with standard reference alanine dosimeters and cellulose triacetate (CTA) films, is essential to ensure the reliability of the whole process [1]. However, variations in the electron energy, beam profiles, attainable dose rate, and conveyor speed also affect the dose absorbed in the irradiated product, requiring constant control and monitoring of these parameters. This task is accomplished with passive dosimeters in static irradiation mode following the international standard recommendations. To broaden the quality control of the irradiation process, it has been proposed to investigate the feasibility of using a homemade diode-based dosimetry system to measure the electron beam profiles and monitor variations in the radiation field in an industrial EB accelerator (DC 1500/25/04JOB188) [2]. This innovative system, when implemented, can provide real-time data, enabling immediate action and avoiding unexpected shutdowns, thereby enhancing the efficiency of the process. The dosimetry probe comprises a commercial diode (230 µm thick; 7.0 mm2 area), with the p+ front pad connected to the Keithley 6517B electrometer in the short-circuit mode. In dynamic mode, irradiations are carried out by sending the probe through the radiation field in the conveyor direction, varying speeds from 2 to 10 m/min. For reference, static measurements are also gathered with alanine pellets and cellulose triacetate (CTA) films. Regardless of the irradiation modes and the dosimeter types, the beam profiles and dose measurements are in good agreement, as shown in Fig.1. The data reproducibility remains to be investigated.
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Resumo IPEN-doc 31029 Implementation of a procedure for calibrating parallel plate ionization chambers in energy X-ray beams
2024 - DIAS, F.S.; JUNIOR RODRIGUES, O.; POTIENS, M.P.A
Radiotherapy can be a low-cost method of treating cancer if appropriate diagnostic and therapeutic equipment, associated with well-trained staff, is available. Among the various modalities available for treatment, intraoperative radiotherapy (IORT) is a good option as it is a method based on a high dose of radiation administered to the tumor bed immediately after surgical excision, thus reducing treatment time.[1,2] IORT can be obtained using miniature accelerators capable of producing low-energy X-rays with voltages ranging from 30 to 50 kilovolts, for example, in the ZEISS INTRABEAM system (Carl Zeiss Meditec AG, Jena, Germany) present in hospitals such as Oswaldo Cruz and AC.Camargo in São Paulo, Brazil. [3] One of the difficulties related to this system is carrying out adequate dosimetry and calibration of the system. According to the recently updated TRS 398 recommendations, for the use of low energy beams, the ideal is to use a parallel plate ionization chamber calibrated in terms of absorbed dose in water. [4] Thus, this work aimed to establish a calibration procedure for parallel plate ionization chambers in terms of absorbed dose in water at the Ionizing Radiation Metrology Center (CEMRI) at the Institute for Energy and Nuclear Research (IPEN). To confirm the procedure, the calibration of 4 parallel plate ionization chambers was carried out, including one belonging to a private hospital.