Author: Ana Laura Burin, Maysa Müller Ferreira Gesserame, David Alexander Urbina Leal, Ilca Marli Moitinho Amaral Medeiros, Silas Leonel Pereira Miranda, Thuany Corrêa Nogueira, Maria da Penha Alburquerque Potiens, Pedro Henrique Ricardo, Maria Eduarda Zaganin Rigo, Orlando Rodrigues, Priscila Santos Rodrigues, Wilmmer Alexander Arcos Rosero, Maria Elisa Chuery Martins Rostelato, Sabrina Spigaroli Sgrignoli, Ana Catarina Koka de Souza Silva, Cristhian Ferreira Talacimon, Paulo Victor dos Santos Tavares, Lara El Hajj Teodoro, Carlos Alberto Zeituni, José Neres de Almeida 👨🔬
Affiliation: IPEN - USP 🌍
Purpose: Perform three-dimensional dosimetry of radioactive gold nanoparticles (¹⁹⁸AuNPs) using Fricke xylenol gel (FXG), aiming to determine the dose distribution and evaluate the method's effectiveness with radioactive nanoparticles.
Methods: The ¹⁹⁸AuNPs were produced by irradiating ¹⁹⁷Au to produce ¹⁹⁸Au, which was subsequently transformed into H¹⁹⁸AuCl₄, the primary precursor for nanoparticle fabrication. To the H198AuCl₄ solution, 0.02 mM gum arabic, 39 mM sodium citrate, and 13 mM sodium hydroxide were added. These compounds acted as stabilizing and nucleating agents, facilitating the formation of ¹⁹⁸AuNPs, which are characterized by their wine-red color. The FXG dosimeters were composed of 5% bovine gelatin 270 Bloom, 50 mM sulfuric acid, 1 mM sodium chloride, 1 mM ammonium ferrous sulfate, 0.01 mM xylenol orange, and ultrapure water. The formulation was homogenized at 35°C, stored in flasks designed for the CT Vista 16 scanner, and refrigerated until reaching a gel-like consistency. FXG measurements were conducted after 6, 8, and 10 hours of interaction with about 1 mL of ¹⁹⁸AuNPs (31.45 MBq). The Monte Carlo simulation modeling using the TOPAS code was adjusted to replicate the real experiment.
Results: Optical computed tomography (OCT) enabled the three-dimensional mapping of the dose and identification of its distribution along the depth. The maximum doses correlated with the irradiation period, showing a decreasing gradient in the ¹⁹⁸AuNPs region. Moreover, the experimental results were consistent with the Monte Carlo simulations.
Conclusion: The three-dimensional dosimetry utilizing FXG and OCT analysis enabled the determination of the dose distribution of ¹⁹⁸AuNPs, with results consistent with Monte Carlo simulations. In the results, it is presented a direct relationship between irradiation time and maximum doses, highlighting the method's effectiveness in evaluating dose deposition at short distances due to radioactive nanoparticles. The findings confirm the potential of this methodology, highlighting it as a promising tool to enhance theranostic applications.