Speaker
Description
C. Bălan1,2 *, C. Oancea3, G. Mytsin4, S. Shvidky4, A. Molokanov4, V. Chiș1, C. Granja3
1. Faculty of Physics, Babeș-Bolyai University, Cluj-Napoca, Romania
2. Radiotherapy Department, The Oncology Institute “Prof. Dr. Ion Chiricuta”, Cluj-Napoca, Romania
3. ADVACAM, Prague, Czech Republic
4. Joint Institute for Nuclear Research (JINR), Dzhelepov Laboratory of Nuclear Problems, Dubna
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Corresponding Author: cristina.balan@ubbcluj.ro
Proton therapy is expanding its application to a greater number of patients. Therefore, the number of cases that will undergo treatment include patients with implants and other metallic objects. This should be considered in the planning system and their impact regarding the dose deposition must be precisely evaluated [1], [2]. For this reason, in this work we experimentally investigate the composition and spectral characterization of scattered particles and the secondary field produced behind the Bragg peak (BP) in tissue-equivalent phantoms with titanium (Ti) dental implants placed along the primary beam path.
Using high-spatial resolution and time-sensitive imaging detectors in a high granularity pixelated array provided by the ASIC chip Timepix3 with silicon sensor, we measure in detail the scattered radiation field with spectral and tracking analysis [3]. The mixed particle field was produced by a collimated 170 MeV proton beam. PMMA plates (140 mm H20) were inserted in the beam path to reach the BP at the region of the metallic implants. Two pixel detectors with Si sensors of different thicknesses, 500 and 300 µm respectively, were placed behind the phantom (see Fig. 1a) along the axis of the incident proton beam. The detailed registration of scattered particles measured by Timepix3 behind the phantom is shown in figure 1b. The scattered radiation is analyzed in terms of LET spectra and composition Recognition of particle type events [3] is based on extensive experimental calibrations in well-defined radiation fields as well as with AI and machine learning algorithms [4]. The resulting particle flux in both setups are resolved: high-energy transfer particles (HETP) namely protons and low-energy transfer particles (LETP) namely electrons together with X and low-energy gamma rays. Protons are the predominant particle responsible for dose deposition after the BP. Without significant variation in particle flux when the Ti implants are placed in the beam’s path, 285 particles·cm-2·s-1 without them, and 263 particles·cm-2·s-1 with metallic inserts, the contribution of particles like electrons, X rays, gamma particles to the particle fluxes is affected by the present of high Z material in the irradiation field. Comprehensive evaluation of the scattered radiation field provides a detailed understanding of the impact of Ti materials on dose deposition escalation to highlight the possible radiobiological implication in proton treatments.
References:
[1] C. Oancea, et al. Phys Med Biol 63 (2018) 215020
[2] C. Oancea, et al. Radiat Meas 110 (2018) 7–13
[3] C. Granja, et al. IEEE TNS 71 (2024) 921-931
[4] L. Marek, et al. JINST (2023)
Acknowledgments
Experiments performed in 2019 in frame of Research Project 04-2-1132-2017/2022 by JINR-RO agreement, and by Research Project 04-2-1132-2017/2022 from the Czech Committee for Cooperation with JINR Dubna of the Czech Ministry of Education.
