The aim of this project is to fabricate hydrogen-rich silicone doped with magnetic nanoparticles for use as a temperature change indicator in magnetic resonance imaging-guided (MRIg) thermal ablations. To avoid clustering, the particles of mixed MnZn ferrite were synthesized directly in a medical-grade silicone polymer solution. The particles were characterized by transmission electron microscopy, powder X-ray diffraction, soft X-ray absorption spectroscopy, vibrating sample magnetometry, temperature-dependent nuclear magnetic resonance relaxometry (20 °C to 60 °C, at 3.0 T), and magnetic resonance imaging (at 3.0 T). Synthesized nanoparticles were the size of 4.4 nm ± 2.1 nm and exhibited superparamagnetic behavior. Bulk silicone material showed a good shape stability within the study's temperature range. Embedded nanoparticles did not influence spin-lattice relaxation, but they shorten the longer component of spin-spin nuclear relaxation times of silicone's protons. However, these protons exhibited an extremely high r2* relaxivity (above 1200 L s-1 mmol-1) due to the presence of particles, with a moderate decrease in the magnetization with temperature. With an increased temperature decrease of r2*, this ferro-silicone can be potentially used as a temperature indicator in high-temperature MRIg ablations (40 °C to 60 °C).
Keywords: MRI; MRI-guided surgery; NMR; ferrite; nanoparticles; silicone.