LUCAS VERDI ANGELOCCI
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Resumo IPEN-doc 31144 Dose rate by distance for Au-198 nanoparticles in water2024 - ANGELOCCI, L.V.; SGRIGNOLI, S.S.; SOUZA, C.D.; TEODORO, L.E.H.; ZEITUNI, C.A.; ROSTELATO, M.E.C.M.Purpose: To evaluate dose as a function of depth in water medium by a source of Au-198 nanoparticles, both as a point source and as homogeneously distributed over a volume representing a prostate tumor. Dose over an unidirectional axis was estimated and presented according to distance from the source, highlighting nearby organs at risk. The aim of the work is the first step in the dosimetric characterization of a new source for nanobrachytherapy under development, consisting of Au-198 nanoparticles injected directly in tumoral mass. Methods: Simulations were carried using MCNP6.2 code by Los Alamos National Laboratory. Four different simulations were realized, for two different source configurations (point source and 0.4 cm radius spherical source, modeling a prostate tumor) each considering two different components for the dose (beta emission and photon (gamma/x-ray) emission from the source). Medium considered was infinite water homogeneous. Results: Dose curve as a function of distance from the source was evaluated and allowed a first estimative of dose at points of interest for treatment with a new nanobrachytehrapy source. Point source results are valuable for future extrapolation for complex tumor/organs geometry. Prostate tumor model presents data that allows to estimate dose at center of tumor, borders of tumor, and at other organs nearby, such as rectum and bladder. Conclusion: Being a beta-emitter, Au-198 shows a high deposition of energy near the source, with doses falling significantly with distance from the source. However, due to gamma and x-ray emission from the source, as well as secondary radiation originating from the beta particles, not-negligible dose was scored at significant distance. This quantitative study will be relevant for posterior dosimetry of more complex cases as well to develop protocols for dosimetry and clinical use, as nanobrachytherapy (with nanoparticles as sources) is a relatively new field with few specific works published.Resumo IPEN-doc 31143 Study of a new formulation for a phosphorus-32 polymeric source for use in brachytherapy2024 - TEODORO, L.E.H.; TALACIMON, C.F.; SILVA, A.C.K.D.S.; BURIN, A.L.; MEDEIROS, I.M.M.A.; RIGO, M.E.Z.; RODRIGUES, P.S.; TAVARES, P.V.D.S.; SGRIGNOLI, S.S.; ANGELOCCI, L.V.; VIEIRA, J.M.; ZEITUNI, C.A.; ROSTELATO, M.E.C.M.Purpose: To evaluate a new material for a phosphorus-32 polymeric film to use in brachytherapy for paraspinal and intracranial tumors and to analyze its activity distribution. Methods: As phosphorus-32 comes in the form of orthophosphoric acid, several tests were conducted to determine the best resin to encapsulate it. Initially, acid without radiation was used. Each test was repeated at least five times to ensure its result. Two variables were checked to evaluate the results: whether the resin cured or not, and if the final product was flexible. All tests were conducted with the selected resin being poured in molds of 5.0 x 5.0 x 0.04 cm. After selecting the considered suitable resins, acid with the active phosphorus-32 was used to produce the source. The film’s activity was measured on an ionization chamber detector. After measuring the activity from the whole film, it was cut into pieces of 1.0 x 1.0 cm and then measured again to verify the activity’s distribution. Results: From the resin tests, two of them stood out, for both their curing properties and malleability: silicone rubber with platinum catalyst and polyvinyl alcohol (PVA). Other resins evaluated whether did not cure or the film was considered not flexible. The activity measurements for the silicone rubber samples had a mean value of 227.92 ± 1.30 MBq (or 6.160 ± 0.005 mCi) and the distribution was acceptable. For the PVA, the activity mean value was 243.09 ± 1.39 MBq (or 6,573 ± 0.005 mCi) and the distribution was also acceptable. Conclusion: This work indicates a potential for a new flexible brachytherapy source, which could improve the surgical technique for central nervous system tumor resection and treatment. The activity results were promising according to the literature for a HDR source and further investigation on its dosimetry is needed to evaluate it.Resumo IPEN-doc 28462 Assessing Ir-192 as an alternative to I-125 in ophthalmic treatment2020 - ANGELOCCI, L.; NOGUEIRA, B.R.; SOUZA, C.D. de; ZEITUNI, C.A.; ROSTELATO, M.E.C.M.Purpose or Objective: Brachytherapy sources for ocular melanoma usually contain Co-60, I-125, Pd-103 or Ru/Rh-106 as radionuclides. Ir-192 is not a preconized radioactive material for this purpose, although it is used for other brachytherapy applications. Higher mean energy from Ir-192 emission (ca. 380 keV) may be a reason for the preference of I-125 (35 keV) or Pd-103 (21 keV) over it, since low penetration is desired on the small structures of the human eye. This is not, however, an excluding criterion, considering Co-60 and Ru/Rh-106 have even higher mean energies. The demand in Brazil for lower-cost seeds to treat ocular melanoma lead to the development of an Ir-192 seed to make treatment more accessible, but since it is not used as an ophthalmic brachytherapy source, before its dosimetry is considered, one should care about the possibility of using it over more stablished materials. Considering this, the aim of this work is to assess the possibility of using Ir-192 seeds as ophthalmic brachytherapy sources by comparing some dosimetric parameters of a new seed model with the most stablished I-125 seed in literature, OncoSeed 6711. Material and Methods: As an initial study on the topic, this work relies only on Monte-Carlo simulations using MCNP4C transport code. Parameters analyzed are air-kerma strength, dose-rate constant and depth-dose curve, attention given to points within the human eye dimensions. The medium considered was homogeneous water, as it is a good approximation to the eye tissues in terms of composition and density and allows for future comparisons with TG-43 based calculations. OncoSeed 6711 is not produced anymore, but its long term as the reference source for dosimetry was considered. A 20 mm COMS ophthalmic applicator was also modeled and considered to be fully loaded with each seed model to compare the same parameters at a realistically clinical approach. Results: As expected, due to the higher energy of the Ir-192 emission spectrum, dose fall-off on the transversal axis of the seeds is less pronounced for the new seed model. The steeper dose gradient for I-125 is also visible on the doserate constant value. The effect of using a COMS applicator only strengthens this characteristic. Depth-dose curves were calculated up to the distance of 5 cm, both for a single seed and for an applicator fully loaded with 24 seeds. All the eye components relevant for dosimetry are located within this range, like the cells of the crystallin and the optical nerve. Conclusion: If one expects to use Ir-192 as an alternative to I-125 in ophthalmic cancer treatment, at least the dosimetry following TG-43 protocol should be carried with utmost attention, as undesirable dose to healthy nearby tissues is unavoidable. Crafting a different applicator most suited for this radionuclide is a possibility that can be taken into account. Another recommendation is to go beyond TG-43 water-based protocol and actually estimate dose to relevant eye components.