- 學位論文
高溫腫瘤治療超音波換能器設計與分析
Design and Analysis of Ultrasound Transducers for Hyperthermia
摘要
實驗顯示，動物組織細胞在42~45℃高溫中，會發生凝固性壞死(coagulation necrosis)，其存活率也會隨著加熱時間的增長環境而降低，並且放射線治療配合高溫治療增加其療效因為熱能可以破壞細胞對輻射能的抵抗能力。利用超音波具有波長短、穿透力強特性，作為高溫腫瘤治療之加熱工具。針對各別的腫瘤深度、大小，運用超音波因壓電片的形狀、半徑的差異所產生不同的能量分佈，從事設計所需的換能器提供腫瘤治療使用。 本文是以波動理論與生物熱傳方程式作為研究理論的推導基礎，分別用來分析超音波在果凍內的強度及熱傳導現像所造成的溫度分佈情況。首先以數值方法求出不同直徑不同放射頻率的超音波換能器所產生波壓分佈，並模擬在果凍內插入熱電偶量在不同位置上超音波能量所造成的溫度上升情形，用數值方法求解以生物熱傳方程式在不同的超音波能量下，整個溫度場變化情形。 本研究除了數值分析超音波換能器所產生的波壓、溫度分佈外，也製作一超音波換能器然後以此換能器作為加熱工具在果凍模型放射超音波波束，模擬超音波高溫治療，利用溫度量測系統量取不同位置溫度上升情形，並實際量測其波壓分佈清況，以AIMS(Acoustic Intensity Measurement System)與溫度量測系統 ( 2701 Ethernet Multimeter / Data Acquisition system)，實驗分析結果作為腫瘤治療所需使用的超音波換能器設計依據。
並列摘要
It has been shown that 60% of animal’s cells can be killed when their temperatures rise to 42℃ between 45℃ for 30 minutes due to the coagulation necrcosis. The survival rate was decreasing when temperature increased. Ultrasound has several characteristics, such as, small wavelength, deep pentration, which make it well suited for hymperthermia. The goodness of the combination of radiation therapy and hyperthermia is enhanced because the heat can decrease the cell’s radiation resistance about radiation. For tumors with different lecations and sizes , one can design appropriate ultrasound transducers with different shapes and sizes to provide ultrasound power distributions for hyperthermia treatments. This study is based on the theoretical studies of the wave theory and the bio-heat transfer equation to analyze the ultrasound intensity and temperature distribution a tissue-mimick material, jello. First, we calculate the transient temperature responses at several locations using the bio-heat transfer equation. Besides, we also fabricate ultrasound transducers and use them as heating sources to simulate the heating process of a hyperthermia treatment. We make a tissue mimck material using jello to simulate a tissue without blood flow. We use AIMS (Acoustic Intensity Measurement System) to measure the acoustic pressure fields of ultrasound transducers, and a data acquisition system (2701Ethernet Multimeter/Data Acquisition system) to measure the temperature responses at different locations during the heating process. Results can provide useful information about the design of ultrasound transducers for hyperthermia.