Subcutaneous Layer

The subcutaneous layer is the tissue beneath the dermis, made up mainly of fat and connective structures, and it's the deepest layer that HIFU devices can be calibrated to reach. Using deeper cartridge settings, focused ultrasound energy can be directed into this layer to heat and tighten the fibrous septa (the connective bands running through subcutaneous fat), which can contribute to a firmer, more contoured appearance in areas where localised fat and skin laxity occur together — such as under the chin or along the jawline. This is a different mechanism from the collagen stimulation that happens in the dermis: here, the focus is on the connective tissue structure surrounding fat cells rather than collagen density in the skin itself. On ULTRAISER devices, subcutaneous-depth treatment requires the deeper cartridge settings (4mm and beyond), rather than the standard 2mm cartridge used for general facial skin tightening.