# Thermal Accumulation and Collagen Remodeling in Porcine Models: Parameter‐Dependent Efficacy of Micro‐Focused Ultrasound for Human Facial Skin Tightening

## TL;DR

This study explores how micro-focused ultrasound can tighten facial skin by using precise thermal energy in porcine models and human patients.

## Contribution

The study introduces parameter-dependent thermal accumulation and safety thresholds for optimizing micro-focused ultrasound protocols.

## Key findings

- Peak temperatures align with preset focal depths using different handpieces and energy levels.
- MFU achieves significant facial skin tightening with minimal adverse effects.
- Thermal accumulation increases with higher energy and longer exposure durations.

## Abstract

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.

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.

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.

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.

MFU‐induced thermal peaks align with preset focal depths, demonstrating parameter‐dependent thermal accumulation. The procedure safely achieves clinically significant facial skin tightening.