Dynamic high-resolution ultrasound in vivo imaging of hyaluronic acid filler injection.

[BACKGROUND] High-resolution ultrasound (HRU) imaging is a useful tool to study hyaluronic acid (HA) filler injected in the face.

[OBJECTIVE] To observe real-time injection of HA using HRU and describe behavior of the gel injection in various anatomic layers and the effect of massage.

[METHODS] Deep (preperiosteal), intermediate (subdermal), and superficial (dermal) injections of HA were performed in the supraclavicular area under ultrasonography visualization on a healthy volunteer. Videos were obtained during injection and static images at several time points, including during injection, immediately after injection, 5 minutes after massage of the treated area, and at 2 weeks after injection.

[RESULTS] During injection, dermally injected HA stayed within the dermis, increasing its echogenicity; subdermally injected HA formed multiple anechoic pearls; and preperiosteal HA produced a single anechoic bubble with diffuse margins. No vertical transection of the planes was observed during injection or after massage. Two-week postinjection imaging showed persistence of the varying HA morphology in each plane.

[CONCLUSIONS] High-resolution ultrasound allows in vivo study of HA injection behavior. HA adopts different morphology within the tissue depending on the density and compliance of the tissues in the plane of injection.