At this point, the MFU-V depth to achieve the desired outcome needs to be decided. There are two possible goals with MFU-V: skin lifting or skin tightening. For a lifting effect, the SMAS or superficial fascia system (SFS) needs to be targeted. The number of TCPs required to create sufficient tightening and to deposit sufficient new collagen and elastin to achieve a lifting effect needs to be determined. Skin tightening can be achieved by making the skin thicker and, therefore, denser and firmer.To decide the depth of the SMAS and SFS, the physician must master the ability to identify these layers through real-time ultrasound visualization. This is important because a recent study by Casabona et al34 showed that the SMAS and SFS can change with age, gender, and body mass index (BMI), and in different areas of the face and body (Figures 4 A,B).35,37Another study38 showed that patients who received a customized transducer selection based on ultrasound visualization were far more satisfied with results after MFU-V alone (Figures 5 A–C). In conclusion, if the MFU-V treatment lines are not directed exactly to the appropriate tissue layers, the procedure can be less effective, leading to frustration with the final results.
In this step, the physician should check the number of lines needed based on two parameters: the transducer to use and the coverage area provided by each one, according to appearance, severity, and treatment goal. The amount of collagen that MFU-V can produce depends on the number of lines and therefore the linear coverage or density of lines in the same area (Figures 6 A,B). A recent study published by Sasaki et al39 showed more treatment lines produce better clinical results. It would be logical to conclude that different severities would require different density of lines or even different number of