Ultrasound patterns of different dermal filler materials used in aesthetics.

Background Hyaluronic acid (HA) injection procedures has experienced an unprecedented increase. Aims To assess and determine, by using ultrasound examinations, the patterns corresponding to different dermal fillers. Patients/Methods Observational and retrospective bicenter study conducted on patients who underwent previous aesthetic treatments with dermal fillers. Ultrasound examinations were performed, at each study center, by one experienced observer. Results Sixty patients were included in the analysis. Among them, 48 patients showed a well-defined ultrasound pattern, while 12 exhibited a mixed one. According to ultrasound images, 4 different patterns were identified: [1] Heterogeneous, characterized by alternating hyperechoic and anechoic areas, which are visualized in the tissue in a heterogeneous way. This pattern is associated with healthy skin/subcutaneous cellular tissue and with fully integrated HA fillers. [2] Fine grain snowfall, characterized by alternating hyperechoic imaging, with posterior echogenic shadows. It is typical of liquid injectable silicone. [3] Coarse grain snowfall, characterized by hyperechoic images distributed all over the tissue. This is typical of calcium hydroxyapatite and polymethyl methacrylate-based fillers. [4] Globular, typical "cystic" imaging, with anechoic images indicative of liquid semi-liquid content. This pattern is characteristic of polyalkylamides and polyacrylamides, and HA-based fillers immediately after their injection. The presence of "mixed" patterns is mainly due to different aesthetic procedures performed at different times. Conclusions Ultrasound imaging may be a valuable tool for assessing the nature of former dermal filler procedures in daily practice. The identification of these patterns will allow specialists to choose the best therapeutic approach in patients who underwent previous aesthetictreatments.