利用低頻超音波產生空蝕化現象強化高頻熱效應之研究

Abstract

本篇論文主要在探討，空蝕化現象(Cavitation)對焦斑(Lesion)形成的影響。我們使用不同高低頻(1.155KHz+0.577MHz 1.155MHz+28KHz)，以及波源輻照特性(0.577MHz為聚焦型換能器，28KHz為平面型換能器)的搭配去對仿體與豬肉組織進行燒灼，比較經超音波燒灼後，焦斑的大小和差異。從實驗結果可以發現，高頻結合聚焦型低頻超音波產生的焦斑，可以做到區域性增強加熱並保護重要組織的功能；高頻結合平面型低頻超音波產生的焦斑，可在組織深部變長變寬而不會造成前場過熱。我們利用水診器(Hydrophone)去測量子諧波訊號(Sub-harmonic)的方式驗證空蝕化現象是否真的發生。未來在臨床治療運用上，如果可以適當的利用這兩種治療策略，便可以有效地增進整體熱治療的效果。

This study is focused on the effect of cavitation on the process of thermal lesions formation. Different frequencies (1.155MHz + 0.577MHz,1.155MHz + 28KHz) and different types of transducers (focused transducer for 0.577MHz frequency, plan transducer for 28KHz frequency) were applied for heating phantoms and porcine muscle tissue. The differences in size and shape of the formed lesions were compared. The experimental results showed that the combination of high frequency and low-frequency focused transducer produced thermal lesion locally. On the other hand, the combination of high frequency and low-frequency plane transducer produced lager and wider lesion without over heating. The existence of cavitation was monitored by detecting the emitting signals using a hydrophone placed inside the tested samples. If use these novel strategies properly, the efficiency of thermal therapy in the clinical application would be enhanced.