MRI of silicone vitreous ocular implants with phantom correlation.

We imaged two patients who had silicone oil injected their vitreous cavities. The images demonstrated an increased chemical shift artifact. We developed and tested an in vitro silicone oil model in an attempt to explain this. To our knowledge, this artifact has not been previously described. We constructed a phantom using medication cups containing water, lard and two types of silicone. Background control baths of water and lard were used to simulate different local environments. The phantoms were imaged with T1-and T2-weighted and T1-weighted fat suppression sequences. The artifacts were due to the pronounced chemical shift of silicone in relation to intraconal fat. Our model accurately reproduced our clinical images. Spectral analysis of the silicone model revealed different resonating frequencies for fat/silicone, thereby explaining the pronounced chemical shift artifact.