In vivo localized proton NMR spectroscopy of silicone

1H NMR localized spectroscopy (STEAM) can assess unambiguously the presence of free chemically unchanged silicone in animal tissue after injection of silicone oil. Although the signal-to-noise ratio obtained in 1H imaging is sufficient to detect the distribution of relatively large amounts of silicone in vivo, the specificity of silicone detection can be improved by using 1H localized spectroscopy techniques. The sensitivity of the STEAM experiments is sufficient to detect silicone at a concentration of 0.5% in a voxel of 27 mm3. Preliminary results from rats with silicone gel-filled implants show no detectable amounts of silicone in sites such as lymph nodes, the liver or the spleen, 3 or 6 months after implantation.