LITHIUM SILICATE GLASS MICROSPHERES AS REAL-TIME DOSIMETERS FOR HIGH DOSE RATE BRACHYTHERAPY IN PROSTATE CANCER TREATMENT

Abstract

In vivo dosimetry in high dose rate brachytherapy (HDR-BT) faces significant challenges related to high-gradient dose distribution and the need for real-time verification during treatment. This study presents the development, characterization, and clinical validation of a new dosimetry system based on lithium silicate glass microspheres (Li2SiO3:Tb) doped with rare earth elements, capable of providing continuous dose measurements during HDR-BT procedures for prostate cancer. The microspheres, with an average diameter of 350µm ± 50µm, were produced using a modified flame blowing technique and characterized regarding their thermoluminescent properties. Dose readout is performed through a hybrid system that combines laser-induced fluorescence spectroscopy (LIF) with conventional thermoluminescence. Experimental results demonstrated a sensitivity of 12.8 mGy⁻¹, linearity in the range of 0.5 Gy to 25 Gy (R² = 0.998), and reproducibility of 1.3% (1σ). In preliminary dosimetric studies, the system showed excellent agreement with dose planning (γ index < 1.0 for 95.7% of evaluated points) and enabled the detection of positional deviations greater than 3 mm in real time.