ECHO-PLANAR CHEMICAL-SHIFT IMAGING OF SILICONE GEL PROSTHESES

We have developed an echo-planar (EP) proton chemical shift imaging (C SI) MR technique that allow us to discriminate the polydimethylsiloxan e (PDMS, silicone) proton MR signal from that of the fat and water pro tons found in tissues, in order to map the distribution of PDMS in hum ans who have silicone gel prostheses. Silicone gel-filled prosthetic i mplants induce histologic changes in the surrounding tissue which are attributed to the leakage of free PDMS from the prosthesis. The T2 rel axation measurements of three silicone gels show that there are two co mponents in them, each with a different degree of molecular mobility. The presence of free silicone is confirmed by chloroform extraction, w hich removed 14-28% of the material. This free polymer present in the gel can pass through the intact or ruptured membrane of the implant in to the surrounding tissue. Our preliminary imaging results indicate th at EP-CSI MR might be useful as a diagnostic technique for implant mal function.