Ho₂O₃-Al₂O₃-SiO₂ Glasses for in vivo Radiotherapy

Glass formation region in the Ho2O3-Al2O3-SiO2 system extended from 9 to 30 mol% Ho2O3. The chemical durability of these glasses was measured in simulated physiological solutions to determine their usefulness for in-vivo radiotherapeutic applications. The dissolution rates of glass plates were barely measurable in distilled water at 37 or 70°C being no more than 4×10^-9 g/cm2 min. Analysis of the test solutions and glass surfaces showed that little if any holmium leached from glass plates or microspheres into distilled water or saline solutions at 37 or 70°C. The dissolution rates of these glasses in 0·1N HCl increased with temperature and with the substitution of Ho2O3 for Al2O3 or SiO2. The density, refractive index, thermal expansion and Vickers hardness increased with Ho2O3 content