In vivo visualization of hyaluronic acid injection by high spatial resolution T2 parametric magnetic resonance images

Background/purpose: In recent years, increasing use of injectable resorbable fillings has been reported for facial wrinkle treatment. However, the physiological processes involved such as the localization and subsequent diffusion of the injected product in skin tissues are poorly documented. This may be noninvasively achieved using quantitative magnetic resonance imaging (MRI), which is duly presented in this pilot study. Methods: Hyaluronic acid (HA) was injected intradermally in the forearm of a young male volunteer. High-resolution MRI scans using a surface antenna were performed just after injection, and after 2, 4 and 9 months. Morphological images were compared with transverse relaxation time (T-2) images computed from a pixel-by-pixel analysis. Results: On high-resolution morphological MR images the HA injection is barely visible, but with quantitative MRI the zone of injection is clearly seen. This is due to HA having a distinctly different transverse relaxation time, T-2 similar to 600 ms, compared with dermal and hypodermal tissues, 35 and 80 ms, respectively. Conclusion: These preliminary results demonstrate the ability of the T-2 images for in vivo visualization of the filler agent and also for characterization of tissue modifications. In addition, the diffusion and progressive degradation of the filler agent can be monitored by T-2 measurements over time.