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| Dermal fillers | Imaging patterns |
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| Autologous fat fillers | The filler has the appearance of low attenuation soft tissue using CT.
On MRI, it appears as a thin pseudocapsule [10]. |
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| Collagen fillers | On CT, collagen appears as fluid attenuation, and the infiltered subcutaneous fat shows a streaky appearance.
MRI may show hypointense on T1 W images and hypertense on T2 W and STIR images because of its high water content [10, 14]. |
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| Calcium hydroxyapatite (CHA) fillers | On CT, CHA presents as intense defined linear streaks or masses that are rounded. After 12 months, the CT filler density diminishes because microspheres get absorbed, and after 24 months, the filler can disappear.
On MRI, T1 W, and T2 W images, CHA fillers exhibit a low to intermediate signal intensity [10, 17]. |
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| Hyaluronic acid (HA) fillers | On CT, soft tissue attenuation is a common sign of HA fillers.
On MRI, HA fillers show substantially hyperintense on T2 W and STIR sequences and hypointense on T1 W sequences due to their high water content. In the first six months after injection, minor postcontrast enhancement is visible, indicating increasing vascularization of the injected tissue [10, 15]. |
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| Poly-l-lactic acid (PLLA) | On CT, it shows soft-tissue attenuation.
On MRI, T2 W images appear hypointense. |
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| Polyalkylimide and polyacrylamide hydrogels (PAAG) | On MRI, PAAG fillers show as hyperintense on T2 W and hypointense on T1 W sequences, and there is no evidence of postcontrast enhancement [10, 16]. |
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| Silicone oil filler | On MRI, its appearance varies depending on its viscosity and purity. On T1 W images, the low viscosity silicone oil appears somewhat hyperintense to water, iso- or slightly hypointense on T2 W images, and hyperintense on the “silicone only” sequence.
On T2 W images, high viscosity silicone oil is hypointense. All tissues except silicone are suppressed in a “silicone-only” sequence
On CT, silicone seems slightly hyperdense [10, 14]. |
| Paraffin | Calcific spherical foci and soft tissue density nodules with a calcific rim are CT findings of “paraffinoma” [10]. |
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