Echo-planar chemical shift imaging of silicone gel prostheses

We have developed an echo-planar (EP) proton chemical shift imaging (CSI) MR technique that allow us to discriminate the polydimethylsiloxane (PDMS, silicone) proton MR signal from that of the fat and water protons found in tissues, in order to map the distribution of PDMA in humans who have silicone gel prostheses. Silicone gel-filled prosthetic implants induce histologic changes in the surrounding tissue which are attributed to the leakage of free PDMS from the prosthesis. The T2 relaxation measurements of three silicone gels show that there are two components in them, each with a different degree of molecular mobility. The presence of free silicone is confirmed by chloroform extraction, which removed 14-28% of the material. This free polymer present in the gel can pass through the intact or ruptured membrane of the implant into the surrounding tissue. Our preliminary imaging results indicate that EP-CSI MR might be useful as a diagnostic technique for implant malfunction.