研發應用於皮膚拉提治療之聚焦超音波系統

Abstract

本研究的目的為針對臉部拉提，開發聚焦型超音波系統來做為治療。高強度聚焦型超音波換能器能使能量集中於焦區內，在短時間內使焦區內的組織產生急遽的溫度上升，以高溫燒灼皮下組織及肌肉筋膜層(Superficial Muscular Aponeurotic System, SMAS)，破壞膠原蛋白鍵結，來達到促進膠原蛋白新生的效果。再者，超音波具有良好的組織穿透能力，能夠以非侵入的方式進行治療。 聚焦型超音波換能器使用純壓電陶瓷，切割後填入環氧樹脂(Epoxy)，再利用模具壓製成型，使其成為聚焦式壓電複合材料。換能器大小為直徑10.0 mm之圓形，曲率半徑為12.0 mm，操作頻率為5.0 MHz。利用函數產生器搭配功率放大器來驅動換能器，透過匹配電路達到最佳輸出功率，並藉由微量天秤來測量其電聲轉換效率。本研究利用溫感水膠燒灼實驗、豬肉離體實驗及大鼠活體實驗來驗證其加熱效果及聚焦特性。此外，透過Labview軟體完成聚焦超音波換能器與機械式掃描機構的系統整合，機械式掃描系統能夠使聚焦超音波換能器一次進行多點精準治療，並有效縮短整體療程時間。 實驗結果顯示，換能器之電聲轉換效率約為44%，在焦區強度1591.5 W/cm2下作用1秒內使52°C溫度感應型水膠產生變色反應。在豬肉離體實驗及大鼠活體實驗中也證實本聚焦型超音波系統能有效破壞皮下膠原蛋白纖維。

In this study, a focused ultrasound system for skin tightening therapy was developed. Focused ultrasound has the ability to concentrate acoustic power to generate a steep temperature elevation at the subcutanous tissue and superficial muscular aponeurotic system (SMAS) to cause collagen denaturation, contraction and remodeling. In addition, ultrasound has a great ability of soft tissue penetration for non-invasive treatments. Piezoelectric ceramics elements were cut and then filled with epoxy. After that, the elements were compressed with a designed mold to make them become focused piezoelectric-composite. The transducer was made with a diameter of 10.0 mm, a radius of curvature of 12.0 mm and operated at a frequency of 5.0 MHz. A function generator was connected to a power amplifier to drive the transducer, and a matching circuit was made to achieve a better output power. The electro-acoustic transfer ratio was measured by a radiation force meter. In this study, we used thermo-sensitive phantom to observe the heating effect, an ex vivo porcine model and an in vivo rat model were used to confirm the heating effect and the characteristics of focal zones. We combined the focused ultrasound system with a mechanical scanning system using Labview software. The focused ultrasound system can treat multiple points precisely to reduce the total treatment time by using the mechanical scanning system. The results showed that the electro-acoustic transfer ratio was about 44% and could reach the lower critical solution temperature (LCST) of the thermo-sensitive hydrogel. Experimental studies in ex vivo porcine model and in vivo rat model showed that the focused ultrasound transducer could effectively cause tissue denaturation. In this study, we developed a focused ultrasound system for skin tightening therapy. The manufacturing process of piezoelectric-composite material and the feasibility of effective sonication were verified. The characteristics of focal zones and the heating effects on tissues by the transducer were confirmed.