Treatment for retinal detachment

Silicone implant for retinal detachment

on CT silicone is hyperdense

on MR silcone is bright on T1 and T2 and demonstrates "super chemical shift" artifact

Chemical Shift

silicone 0.33 ppm

fat about 1.3 ppm

water 4.7 ppm

Larmor frequency at 1.5 T for H nuclei is 63.87 MHz

The difference of 3.4 ppm =217 or close to the 220 Hz that you often see quoted for the frequency difference for fat and water at 1.5 T

The difference between silcone and water is 4.4 ppm. That is why you see "super chemical shift" with silicone.

Q: Silicone is hyperdense on CT. How do patients see if it is so dense?

A: Radiodensity/physical density has nothing to do with the ability to transmit light. Glass is quite dense, yet can be clear.

Scleral band/buckle

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