In Situ Dose Measurements in Brachytherapy Using Scintillation Detectors Based on the Al2O3:C, Al2O3:C,Mg, and GAGG:Ce Crystals

Currently, the use of scintillation crystals connected via optical fiber to a luminescence spectrometer (so-called fiber-optic dosimeters) offers a promising approach for real-time dosimetric measurements during brachytherapy treatments with γ-ray sources. This study aims to evaluate the applicability of fiber-optic dosimeters for in situ dose measurements during brachytherapy procedures, using Al₂O₃:C and Al₂O₃:C,Mg crystals, which have near-tissue density and effective atomic number (ρ = 3.99 g/cm³, Z_eff = 10.8), as well as heavy GAGG:Ce scintillation crystals (ρ = 6.63 g/cm³, Z_eff = 54.4). Radiation dose delivery was assessed through measurements of the resulting radioluminescence of the aforementioned scintillation crystals, connected via long optical fibers and recorded with highly sensitive, compact luminescence spectrometers. Measurements were performed in a dedicated phantom under clinical conditions at the Oncology Center in Bydgoszcz, Poland. The dosimeters were evaluated for in situ dose monitoring within the 0.5-8 Gy range during brachytherapy procedures using a ¹⁹²Ir (392 keV) source. The results showed a clear linear relationship between the delivered radiation dose and the scintillation output measured by the fiber-optic detector. The Gd₃Al_2.5Ga_2.5O₁₂:Ce crystal detector exhibited excellent linearity, while the Al₂O₃:C and Al₂O₃:C,Mg crystal detectors also showed a nearly linear dose-response relationship.