S1657
Physics - Detectors, dose measurement and phantoms
ESTRO 2026
combinations of beam energy and MF strength passed the Fano test within 0.2 %, with the highest deviation at 1 T (Q = 0.997 ± 0.0005). Q values decrease with increasing MF strength, a trend aligning with Blum et al. For helium ions, Q values exhibit an under- response, with a maximum deviation of 0.9963 ± 0.0004 at 0.5 T. No pronounced energy dependence was observed for either ion. At 250 MeV/u, reducing the maximum step size from 1 mm (default) to 0.01 mm or omitting this restriction did not improve the results. Varying dRoverRange from 0.01 to 0.5 produced fluctuations for both ions, with the default values yielding the smallest deviations. Similarly, no clear trend was observed with varying final range from 1 nm to 10 µm.
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Developing New Dosimetry Approaches and Addressing Issues in Radiopharmaceutical Solutions in Nuclear Medicine Using Garnet-Based Crystal Detectors Mateusz Wedrowski 1,2 , Artur Majewski-Napierkowski 3 , Yuriy Zorenko 3 1 Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University in Torun, Bydgoszcz, Poland. 2 Nuclear Medicine Department, Oncology Centre in Bydgoszcz, Bydgoszcz, Poland. 3 Faculty of Physics, Kazimierz Wielki University in Bydgoszcz, Bydgoszcz, Poland Purpose/Objective: The aim of our study is to develop a method for the objective assessment of internal organ exposure to radiation during nuclear medical procedures involving different types of ionizing radiation in liquid form. For this purpose, we require radiation detectors that combine high sensitivity, strong luminescence response, and chemical stability for use in dosimetry within nuclear medicine, radiopharmacy, and oncological surgery. This study focuses on the evaluation and optimization of the dosimetric properties of oxide-based crystals such as Y ₃ Al ₅ O ₁₂ :Ce (YAG:Ce), Lu ₃ Al ₅ O ₁₂ :Ce (LuAG:Ce), and Gd ₃ Ga ₅ O ₁₂ :Ce (GGG:Ce) garnets in aqueous solutions containing medical radioisotopes, specifically Tc-99m (γ-source), Y-90 (β-source), and Ra-223 (α-source), using thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques. Material/Methods: The crystal detectors were immersed in controlled aqueous solutions of the aforementioned radioisotopes with known activity, concentration, volume, temperature, and exposure time. The detector responses were measured using TL glow- curve analysis and OSL decay kinetics protocols. Results: All studied crystal detectors exhibited stable and linear responses as a function of radioisotope activity, confirming their suitability for quantitative dosimetry. The effects of Ce³ ⁺ concentration and crystal defect formation (controlled by growth conditions and thermal treatment) on charge trapping and recombination processes were assessed. No single composition demonstrated overall superiority; rather, each material showed distinct advantages depending on the detection conditions. All crystal detectors exhibited excellent chemical stability in aqueous radiopharmaceutical environments.In the TL registration mode, the YAG:Ce detector demonstrated higher responsiveness for the registration of high- activity levels, while LuAG:Ce produced a stronger light output at low activity levels. In contrast, GGG:Ce
Figure 1. Q values for carbon (left) and helium (right) under varying MFs and energies. Conclusion: This work established the Fano test for carbon and helium ions in MFs, achieving agreement within 0.31% and 0.36%, respectively. The results were insensitive to variations in step parameters within each MF strength, although dRoverRange and final range exhibited MF dependence. Notably, the scored energy for helium appears to be underestimated, which requires further
investigation. References:
[1] Kretschmer J, Dulkys A, Brodbek L, Stelljes TS, Looe HK, and Poppe B: Monte Carlo simulated beam quality and perturbation correction factors for ionization chambers in monoenergetic proton beams. Med Phys. 47 (2020), S. 5890-5905. [2] Blum I, Wong JS, Padre KG, Stolzenberg J, Fuchs H, Baumann KS, Poppe B, and Looe HK: Fano cavity test and investigation of the response of the Roos chamber irradiated by proton beams in perpendicular magnetic fields up to 1 T, Phys. Med. Biol., 69 (2024). Keywords: Fano test, MR-guided particle therapy, heavy ions
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