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Abstract: 154-1

154-1

Numerical dosimetry of stereotactic radiosurgery treatments in pediatric patients

Authors:
Daniela Carvalho Silva (PPGEB/UFU - Programa de Pós-Graduação em Engenharia Biomédica, Faculdade de Engenharia Elétrica, Universidade Federal de Uberlândia) ; Alessa Maschio (PPGEB/UFU - Programa de Pós-Graduação em Engenharia Biomédica, Faculdade de Engenharia Elétrica, Universidade Federal de Uberlândia) ; Felipe Beraldo da Cruz (INFIS/UFU - Instituto de Física, Universidade Federal de Uberlândia) ; Arthur de Souza Borges Zuchetti Alves (PPGEB/UFU - Programa de Pós-Graduação em Engenharia Biomédica, Faculdade de Engenharia Elétrica, Universidade Federal de Uberlândia) ; William S. Santos (PPGEB/UFU - Programa de Pós-Graduação em Engenharia Biomédica, Faculdade de Engenharia Elétrica, Universidade Federal de Uberlândia, UFS - Departamento de Física, Universidade Federal de Sergipe) ; Lucio Neves (PPGEB/UFU - Programa de Pós-Graduação em Engenharia Biomédica, Faculdade de Engenharia Elétrica, Universidade Federal de Uberlândia, INFIS/UFU - Instituto de Física, Universidade Federal de Uberlândia) ; Ana Paula Perini (PPGEB/UFU - Programa de Pós-Graduação em Engenharia Biomédica, Faculdade de Engenharia Elétrica, Universidade Federal de Uberlândia, INFIS/UFU - Instituto de Física, Universidade Federal de Uberlândia)

Abstract:

Clinical cases of tumor lesions developing within the brains of patients of various ages are recurrent in any radiotherapy service. When these patients present comorbidities or belong to radiosensitive groups such as pregnant women or children, craniotomy and conventional radiotherapy techniques can be risky for treatment [1]. In this context, the use of stereotactic radiosurgery (SRS) can be a non-invasive alternative for pediatric patients who need this type of care, as it delivers a high dose of radiation to a millimetrically defined target. The main concern in this procedure is regarding radiation exposure to organs outside the treatment field, where it is expected that doses will be higher when compared to a similar irradiation situation in adults due to the smaller body size [1]. To determine the conversion coefficients (CC) in SRS, computer simulations were performed using the Monte Carlo method with the MCNP6.3 code [2], utilizing the tally F6 (MeV/g/source-particle). The 201 sources of 60Co [3] of a Gamma Knife unit were located on the surface of a cone, so that the photon beams converged to the isocenter. The Paediatric Mesh-type Reference Computational Phantoms [4] of different ages can be imported into 3D modeling software to set up a radiosurgery scenario. The geometry can be exported and converted to a mesh format accepted by MCNP through the POLY2TET code [5]. The results indicated that younger pediatric patients received higher doses of scattered radiation in the head-neck region, such as the cornea, aqueous humor, and thyroid. As age increases, the dose decreases in the rest of the body. Thus, the scenarios simulated using the MCNP6.3 code demonstrated that SRS in pediatric patients should be employed with caution due to the higher exposure to scattered radiation doses in organs outside the treatment field, such as the cornea, aqueous humor, and thyroid. This risk is more pronounced in younger patients due to the smaller body size, increasing the chance of adverse effects. Therefore, careful and individualized planning is important to minimize these risks, thus ensuring the efficacy and safety of the treatment.

The authors would like to thank the Brazilian agencies CNPq (Grants 312160/2023-2 (L.P.N), 312124/2021-0 (A.P.P), 309675/2021-9 (W.S.S) and 406303/2022-3), CAPES (88887.951156/2024-00) and FAPEMIG (Grants  APQ-04215-22, APQ-01254-23 and APQ-04348-23).

Keywords:
 Stereotactic radiosurgery, Pediatric dosimetry, Monte Carlo simulations, Radiation exposure, Gamma Knife treatment