The meaningful differences are the energy source, whether heating is focal or diffuse, the device's visualization features, and the treatment plan chosen for the individual anatomy.
Ultherapy Prime (MFU-V): Its transducers create discrete thermal coagulation points at nominal depths of 1.5, 3.0, and 4.5 mm. The integrated DeepSEE system visualizes tissue to 8 mm and shows the planned treatment line before delivery. Ultherapy has indication-specific FDA 510(k) clearances; clearance is not the same as a guarantee of outcome.
Korean HIFU platforms: Ultraformer MPT, Doublo Gold, and other systems also use focused ultrasound, but their cartridges, pulse patterns, visualization features, regulatory authorizations, and clinical evidence are not interchangeable. Ultraformer MPT uses normal and micro-pulse modes; Doublo Gold emphasizes bidirectional delivery. Confirm the exact device and model instead of treating "Korean HIFU" as one standardized protocol.
Thermage FLX (monopolar RF): RF current passes between the treatment tip and a return pad while surface cooling protects the epidermis. Unlike the discrete ultrasound points above, monopolar RF produces broader, diffuse heating through dermal and subdermal tissue. A human histometric comparison found HIFU produced the strongest remodeling in the deep reticular dermis while monopolar RF produced collagen changes across multiple dermal layers (Suh et al., 2015). It is therefore misleading to reduce Thermage to an exact 2–3 mm depth or to say RF affects only superficial tissue. Thermage FLX is FDA-cleared under K170758.
The defensible comparison is focal ultrasound at selected depths versus diffuse monopolar RF heating. Neither mechanism alone determines which option is appropriate or how much visible change an individual patient will have.