LUCAS VERDI ANGELOCCI

LUCAS VERDI ANGELOCCI

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A dosimetric evaluation using the Monte Carlo method considering geometric variations of the iodine-125 seed for brachytherapy
2024 - CHICO, H.S.; ANGELOCCI, L.V.; ZEITUNI, C.A.; SOUZA, C.D.; SGRIGNOLI, S.S.; ROSTELATO, M.E.C.M.
The Institute for Energy and Nuclear Research – IPEN-CNEN/SP is uniquely positioned to develop a new source of Iodine-125 for brachytherapy treatment. Therefore, research into the dosimetric process and source design is widely studied. Task Group 43 – TG 43 cites methodologies for dosimetry of sources for brachytherapy, the most used method is Monte Carlo. However, the dosimetric protocol does not mention possible variations in the source geometry after its conception. The investigative focus of the work was to obtain measurements of the Iodine-125 seed during the production stages until completion, quantify them and simulate them using the Monte Carlo method with the MCNP – 4C code, the formalism was in water and a 101x101 matrix was used to calculate the dose point by point. Two variations were chosen: a) seed length; b) nucleus length, using a batch of 100 seeds for each case. 100 simulations were carried out for each variation and one simulation using the reference seed geometry. The following calculations were applied: relative difference to compare variations to the reference; average among the 100 seeds of each batch to calculate the standard deviation. In both cases there was no point that exceeded 4.48% relative difference, and for standard deviation the largest point was 1.6%, while the Type A uncertainty was 0.018% at the largest point.
New model for an epoxy-based brachytherapy source to be used in spinal cancer treatment
2021 - SILVA, JOSE T.; SOUZA, CARLA D. de; ANGELOCCI, LUCAS V.; ROSERO, WILMMER A.A.; NOGUEIRA, BEATRIZ R.; CORREIA, RUANYTO W.; ZEITUNI, CARLOS A.; ROSTELATO, MARIA E.C.M.
The present work described the cold fabrication of a P-32 radioactive source to be used in CNS cancer using epoxy resin. The epoxy plaque fabricated with Teflon mold presented better agreement. MCNP simulation evaluated the radiation dose. Special attention was given to factors that can impact dose distribution. Average dose was 16.44 ± 2.89% cGy/s. Differences of less than 0.01 cm in thickness within the plaque lead to differences of up to 12% in the dose rate.
Anisotropy function of a new 192-Ir brachytherapy source
2021 - ABREU, R.T.; ANGELOCCI, L.V.; NOGUEIRA, B.R.; SANTOS, H.N.; ZEITUNI, C.A.; ROSTELATO, M.E.C.M.
Brachytherapy is a type of radiotherapy that uses radioactive sources (seeds, wires, among others) close to the tumor. Is important to provide a detailed description of seed dosimetry, so only the tumor will be irradiated avoiding unnecessary dose on adjacent organs and structures. To evaluate the dosimetric parameter of the anisotropy function for a new brachytherapy source, this work proposes the use of microcube TLD-100 dosimeters to find the dose rate using the AAPM Task Group 43 protocol (TG-43). The anisotropy function represents dose distribution around the source and has a major role for characterization of a new iridium source being implemented in Brazil. The value of D(r,θ) was measured using Solid Water phantoms, r value being the distance from the geometric center of the source to the position of the dosimeter on the phantom, and θ being the angle formed between the longitudinal axis of the source and the line connecting the geometric center to the TLD. Monte Carlo calculations were performed to evaluate the anisotropy function to validate the experimental measurements. For each distance value (r), an anisotropy function was plotted (1.0, 2.0, 3.0, 4.0, 5.0, and 10.0 cm). The results obtained with Monte Carlo calculations agreed ±2% with the experimental values for r greater than 3.0 cm, so these results show a good distribution of dose around the seed considering the high energy of 192-Ir (average of 380 KeV) and encapsulation thickness.
Dose-rate constant and air-kerma strength evaluation of a new 125I brachytherapy source using Monte-Carlo
2021 - PRIMO, C.O.; ANGELOCCI, L.V.; KARAM JUNIOR, D.; ZEITUNI, C.A.; ROSTELATO, M.E.C.M.
Brachytherapy is a modality of radiotherapy which treats tumors using ionizing radiation with sources located close to the tumor. The sources can be produced from several radionuclides in various formats, such as Iodine-125 seeds and Iridium-192 wires. In order to produce a new Iodine-125 seed in IPEN/CNEN and ensure its quality, it is essential to describe the seed dosimetry, so when applied in a treatment the lowest possible dose to neighboring healthy tissues can be reached. The report by the AAPM’s Task Group 43 U1 is a document that indicates the dosimetry procedures in brachytherapy based on physical and geometrical parameters. In this study, dose-rate constant and air-kerma strength parameters were simulated using the Monte Carlo radiation transport code MCNP4C. The air-kerma strength is obtained from an ideal modeled seed, since its actual value should be measured for seeds individually in a specialized lab with a Wide-Angle Free-Air Chamber (WAFAC). Dose-rate constant and air-kerma strength are parameters that depends on intrinsic characteristics of the source, i.e. geometry, radionuclide, encapsulation, and together they define the dose-rate to the reference point. Radial dose function describes the dose fall-off with distance from the source. This study presents the values found for these parameters with associated statistical uncertainty, and is part of a larger project that aims the full dosimetry of this new seed model, including experimental measures.
Monte Carlo simulation to assess free space and end-weld thickness variation effects on dose rate for a new Ir-192 brachytherapy source
2021 - ANGELOCCI, LUCAS V.; SOUZA, CARLA D. de; PANTELIS, EVAGGELOS; NOGUEIRA, BEATRIZ R.; ZEITUNI, CARLOS A.; ROSTELATO, MARIA E.C.M.
A new Iridium-192 seed for brachytherapy is under development. Specific dose rate contribution by two different factors were evaluated: the effect from movement of the core in the free space within the seed and the effect of the end-weld thickness variation. Both were investigated through use of the Monte Carlo radiation transport code MCNP6 and an in-house routine programmed with MATLAB. Differences greater than 15% compared to results from the nominal seed were found near the source, indicating a significant dose variation.
New core configuration for the fabrication of 125I radioactive sources for cancer treatment
2020 - SOUZA, CARLA D. de; ZEITUNI, CARLOS A.; FEHER, ANSELMO; MOURA, JOÃO A.; COSTA, OSVALDO L. da; ANGELOCCI, LUCAS V.; ROSTELATO, MARIA E.C.M.
In order to provide prostate brachytherapy treatment for more Brazilian men, IPEN is building a laboratory for the manufacture of radioactive sources. The new methodology for the production of iodine-125 seeds with yield 71.7% ± 5.3%. Points of importance were evaluated/discussed: photo-sensibility, reaction vial type, the substitution for iodine-131, pH, and solution volume. The surface was analyzed by FTIR and EDS. At the end, a Monte Carlo-MCNP6 simulation was performed to evaluate the TG-43 parameters.
Mesh-based human eye anatomy for Monte Carlo dose calculation
2018 - ANGELOCCI, LUCAS V.; YORIYAZ, HELIO
Purpose: The purpose of this work is to explore the capability of the MCNP6 unstructured mesh geometry resources to create an eye and tumor anatomic model for ophthalmic brachytherapy dosimetry. Methods: Abaqus/CAE software was utilized to construct three anatomic eye models using first order tetrahedral mesh elements: a model with a 2 cm in diameter deep tumor; a model with a 1.2 cm in diameter deep tumor; and a model with a 1.2 cm superficial tumor. 2 cm and 1.2 cm COMS applicators fully loaded with Amersham 6711125I seeds were coupled to the eye models for dose calculation using the MCNP6 code. The dose values in the structures of the eye were compared to those obtained using analytical models. Results: Unstructured mesh model has small differences (maximum of 3.4%) in the mass values of the components of the eye comparing to those obtained in the analytical model. Excluding the optical nerve wall, all dose differences were beneath 4% for all structures. The overall dose in the eye agrees within 2% between different models. Conclusions: The feasibility of using unstructured mesh based geometries to model fine structures of the eye has been verified in this study. It was possible to create adequately the anatomic model of the human eye with reproducible dose values compared to reference values.