In situ dose measurements in brachytherapy using scintillation detectors based on the Al2O3:C, Al2O3:C,Mg and GAGG:Ce crystals

Conventional detectors based on ionization chambers, semiconductors or thermoluminescent materials, in principle, cannot be used to verify in vivo the radiation dose delivered during brachytherapy treatments with γ-ray sources. The best approach to use for this purpose of the dosimetric materials based on scintillation crystals. The delivered radiation dose was registered using the radioluminescence response of the crystal scintillator and recorded using very sensitive compact luminescence spectrometers connected to the scintillator via a long optical fiber (so-called fiber-optic dosimeter). This measurement method is completely non-invasive, safe and can be performed in real time. The scintillation crystals can be embedded in the patient's body using a long optical fiber placed intra-cavernously in front of or next to the tumor. The crystals with close-to tissue density can be used in any location, including the respiratory ways, because they do not interfere with dose distribution. However, in the cases of radiation therapy where the detector can be located behind the target, the use of high-density and high-Zeff scintillators is strongly preferred.For the realization of above mentioned task, the scintillation detectors based on the Al2O3:C and Al2O3:C,Mg sapphire crystals with close-to tissue density ρ=3.99 g/cm³ and effective atomic number Zeff=10.8 as well as Gd3Al2.5Ga2.5O12:Ce garnet crystal with high ρ=6.63 g/cm3 and Zeff=54.4 were used in this work. The obtained results are very promising. We observed a very good linear correlation between the dose and scintillation signal registered by detector system based on the Gd3Al2.5Ga2.5O12:Ce garnet crystals. Close to liner dependence dose/scintillation output was obtained also for Al2O3:C and Al2O3:C,Mg crystal detectors. These measurements were performed on specially prepared phantom in the clinical conditions of the Oncology Center in Bydgoszcz, Poland for in-situ measurement of applied dose in the 0.5-8 Gy range at brachytherapy treatment procedure with of 192Ir (392 keV) source.