發展自適性超音波溫度影像監控射頻燒灼

目前治療肝癌較主流的方式中，不外乎手術切除、射頻燒灼療法、經動脈栓塞、化療，以及近來新興之標靶療法等。其中射頻燒灼療法屬於根除性治療中較簡易且有效率的療法，但治療過程中，若血管的冷卻效應使溫度提升不足或持續時間不夠，便會導致治療不完全。本研究採用以超音波為媒介發展具有即時性與自適性的溫度影像監控系統；利用互相關分析方法計算回音訊號偏移，並藉此估測溫度變化。回音訊號偏移主要原因來自於聲速改變與組織的熱膨脹，此兩種效應交互作用對回音訊號造成的影響由係數k代表，但隨著溫度超過43℃或組織結構差異等因素，係數k往往不為常數或固定函數。基於上述情況，本研究透過自適性的概念找出係數k的變化趨勢，藉此達成即時性的溫度監控。實驗中使用不同射頻燒灼的功率對豬肝組織表面進行加熱，並利用紅外線攝影機與熱電偶呈現空間溫度分佈，做為超音波溫度影像結果的對照。由結果顯示，自適性係數k的計算方法於溫度超過45℃後依然能有效估測溫度分佈；有效估測溫度可達70℃，為超音波溫度影像提供一個可行概念。

關鍵字

自適性；超音波溫度影像；射頻燒灼；回音訊號偏移；互相關演算

並列摘要

The main therapeutic method of hepatic tumors includes surgery, ethanol injection, RF ablation, arterial embolization, chemotherapy and targeted therapy. RF ablation is a useful method with several advantages. But cooling effect of the artery may cause the therapy incompletely which may be due in part to the inability to monitor accurately temperature profiles in the tissue being ablated, and to visualize the subsequent zone of necrosis formed. The goal of this study is investigate self-adaptive ultrasonic methods for the real-time and in vivo monitoring of the spatial distribution of heating and temperature elevation. Temperature estimates are obtained using a cross-correlation algorithm to calculate the echo shift applied to ultrasound echo signal data acquired at discrete intervals during heating. The change of the temperature is proportional to the echo shift by coefficient k which is combination of sound speed dependent temperature and thermo expansion of tissues. According to the difference of the temperature and the structure of tissue, coefficient k isn’t always a constant, especially as the temperature is over 43 degree. So we find the coefficient k at different temperature through the self-adaptive concept to monitor the real time temperature change. We use the different power of RF ablation to heating the vitro liver of pigs, and measuring the special temperature profile by infrared camera and thermocouple at the same time. The results showed that, method of self-adaptive coefficient k can estimates temperature accurately even if the temperature is over 43 degree reached to 70 degree.

並列關鍵字

self-adaptive ； ultrasonic temperature image ； RF ablation ； echo shift ； cross correlation

參考文獻

15. 蕭洪岳, 以離體組織實驗模式發展逆散射能量變化為基礎之超音波溫度影像, 2010, 國立台灣大學: 應用力學研究所.

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國際替代計量

發展自適性超音波溫度影像監控射頻燒灼

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