MRI
What is the reason for the MRI signal intensity characteristics for biological and synthetic fillers?
Biological fillers and synthetic fillers feature a high water content or water-binding capabilities and thus follow water signal on MRI and hence are hypointense on T1 weighted images and hyperintense on T2 weighted images and are difficult to differentiate on MRI.
What are the MRI signal intensity characteristics of calcium hydroxyapatite and polytetrafluoroethylene dermal fillers and how can one differentiate these?
Calcium hydroxyapatite is a hypointense signal on both T1-weighted and T2-weighted images, with mild gadolinium enhancement. Polytetrafluoroethylene features similar signal characteristics but has a more linear appearance on MR imaging.
What are the signal intensity characteristics of biological fillers on MRI?
Biological fillers like collagen or hyaluronic acid (HA) are hypointense on T1 and hyperintense on T2 imaging.
What are the signal intensity characteristics of synthetic polyalkylimide and polyacrylamide hydrogels (PAAG) on MRI?
Synthetic PAAG fillers are hypointense on T1 and hyperintense on T2 imaging.
What is the T2 MRI signal intensity characteristic of Poly-l-lactic acid (PLLA) and what happens on FDG PET CT?
Poly-l-lactic acid (PLLA) is hypointense on T2 weighted imaging. On FDG PET CT, there is increased uptake due to the filler-induced subclinical inflammation.
What are the MRI signal intensity characteristics of silicone dermal fillers?
The MRI appearance of silicon facial fillers differs according to viscosity and purity. The low viscosity silicone oil is slightly hyperintense to water on T1 W images, iso- or slightly hypointense to water on T2 W images, and hyperintense on the “silicone only” sequence. High viscosity silicone oil is hypointense on T2 W images. A “silicone-only” sequence is designed to suppress all tissues except silicone. On fat-saturated T1 W images silicone may appear hyperintense and show chemical shift artefact. Post contrast fat-saturated TIW images may show variable enhancement depending on the inflammatory or reactive changes in the surrounding tissues.
Incidental symmetric facial dermal filler globules.
Contrast-enhanced MRI brain is otherwise normal.