ABSTRACT Background Skin laxity, driven by collagen/elastin degradation and aging, is targeted by micro‐focused ultrasound (MFU) through depth‐specific thermal coagulation to induce collagen remodeling, yet parameter‐dependent thermal kinetics and safety thresholds remain underexplored, limiting protocol optimization. Aims To validate the dose‐effect relationship of MFU using in vitro porcine skin tissues and evaluate its safety and efficacy for human facial skin tightening. Methods Porcine skin tissues containing intact skin, fat, and muscle layers were treated with 8D‐DL 3.0, 8D‐DL 4.5, Vmax‐DL 3.0, and Vmax‐DL 4.5 handpieces. Subcutaneous temperatures at depths of 2.0 mm, 3.0 mm, 4.5 mm, and 6.0 mm were recorded under varying parameters (energy levels and exposure durations). Twenty patients undergoing single‐session MFU facial treatment between June and August 2024 were enrolled. Skin tightening outcomes were assessed at 30‐ and 90‐days post‐treatment. Results For 8D‐DL 3.0 and Vmax‐DL 3.0 handpieces, peak temperatures occurred at 3.0 mm depth across all energy levels and exposure durations. For 8D‐DL 4.5 and Vmax‐DL 4.5 handpieces, peak temperatures localized at 4.5 mm. Focal depth temperatures increased significantly with higher energy levels and prolonged exposure. At 30‐ and 90‐days post‐treatment, upward displacement and volume reduction in bilateral cheek and jawline regions were observed. Mild procedural pain was reported, with no adverse events. Conclusion MFU‐induced thermal peaks align with preset focal depths, demonstrating parameter‐dependent thermal accumulation. The procedure safely achieves clinically significant facial skin tightening.
Qi et al. (Sun,) studied this question.