Longevity and Volume Expansion of Hyaluronic Acid Dermal Fillers: A Cross-sectional 3-dimensional Magnetic Resonance Imaging Study

Background: This investigation aims to analyze the volumetric expansion of injectable facial fillers over time using volumetric magnetic resonance imaging (MRI) analysis. Methods: A retrospective cross-sectional study of 14 patients with a recorded history of filler injections underwent quantitative MRI evaluations. The volume measured was then compared with the documented volume of filler injected. This study focused on detailed volume measurements in anatomically critical zones, including the tear trough, malar region, midcheek, zygoma, and nasolabial region. Results: Volumetric analysis revealed that MRI-measured volumes substantially exceeded the injected volume of filler, with a ratio of 1:2.8. Specifically, total MRI-measured volumes varied from 0.7 to 38 cm 3 , contrasting with initial injected volumes ranging from 0.55 to 11 cm 3 . Conclusions: This is the first study to compare the initial volume of injected hyaluronic acid (HA) filler with the volume detected using 3-dimensional MRI. Certain HA fillers may undergo significant volumetric expansion after administration rather than gradual diminution. These findings contribute to our understanding of the behavior of HA fillers and may explain postinjection edema. This phenomenon should be carefully considered when planning such treatments. These results also demonstrate the benefits of using advanced imaging modalities such as MRI to aid accurate topographical analysis, assessment of residual filler, and prediction of long-term volumetric outcomes in the relevant aesthetic patient.