研發應用於皮膚拉提治療用之二維加熱系統及聚焦超音波換能器

Abstract

本研究利用壓電複合材料研發用於皮膚拉提的聚焦式超音波系統，高強度聚焦式超音波換能器使能量集中在皮下組織的表淺筋膜層(SMAS)，使該層的膠原蛋白分子鏈結因高溫而造成破壞，而產生的熱效應讓鬆散的膠原蛋白重新聚集、緊實來達到皮膚緊緻拉提的效果，並因為超音波在高頻驅動下衰減系數會增高的特性，來將聚焦位置達到皮膚組織，故設定換能器的驅動頻率為5.0 MHz。 本研究製作的超音波聚焦換能器比前人所製作的換能器差異在於探頭的面積，前人所製作的換能器探頭面積過小(探頭直徑為10.0 mm、曲率半徑為12.0 mm、驅動頻率為5.0 MHz)，其耐受性較低，因此與機械式掃描系統搭配時無法完整的進行多點連續治療。本研究製作之超音波換能器面積為前人所製作的四倍(直徑為20.0 mm、曲率半徑為16.0 mm、驅動頻率為5.0 MHz)，其耐受性更好，並且開發搭配超音波換能器的二維機械式掃描系統，除了增加治療精準度及減少治療時程之外，並利用二維掃描的方式達到一次性大面積的廣域治療。 實驗結果顯示，利用PZT841所製作換能器的電聲轉換效率僅約15 %，不足以讓52 °C溫度感應型水膠產生熱效應；而利用PZT880所製作換能器的電聲轉換效率有達到46 – 57 %，能夠使水膠在聚焦區的位置從透明狀變為白色混濁狀，確定有產生熱效應。除了完成自製的聚焦式超音波換能器搭配前人設計一維機械式掃描系統在水膠中進行一次性的多點治療之外，成功開發二維機械式掃描系統並利用Labview軟體與NI myRIO進行系統整合，成功的在雙液型矽膠中達到一次性的大面積廣域掃描，並確認在矽膠中的聚焦效果。

In this study, a focused ultrasound system for skin tightening therapy was developed with piezoelectric-composite. High intensity 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. Ultrasound has a higher absorption coefficient for a higher driving frequency. For the skin tightening, the focus position is reached the skin tissue and the driving frequency of the transducer was set to 5.0 MHz . In this study, the surface area of ultrasound transducer is four times larger than the previous one (Diameter of 20.0 mm, a radius of curvature of 16.0 mm and operated at a frequency of 5.0 MHz). A two-dimensional (2-D) mechanical scanning system was also developed to couple with the ultrasound transducer for a 2-D sequential heating. The use of 2-D scanning can increase treatment accuracy and reduce the treatment time for a large skin area treatment. The results showed that the electro-acoustic transfer ratio was only about 15% for a PZT-841 transducer and it was not able to reach the lower critical solution temperature (LCST) of the thermo-sensitive hydrogel. While the electro-acoustic transfer ratio was about 46-57 % for a transducer made of PZT-880, and it could reach LCST at the transducer focal zone to produce an effective thermal response. In this study, we use the homemade focused ultrasound transducer with the previously designed one-dimensional mechanical scanning system for multi-point treatment in hydrogel. We also developed a 2-D mechanical scanning system and used Labview software with NI myRIO system integration, to achieve a wide-area scanning and confirmed 2-D scanning therapy in the silicone.