陳俊杉臺灣大學:土木工程學研究所范紋鳳Fan, Wen-FengWen-FengFan2010-07-012018-07-092010-07-012018-07-092009U0001-3107200906375100http://ntur.lib.ntu.edu.tw//handle/246246/187913高強度聚焦型超音波(high intensity focused ultrasound, HIFU)治療的置入氣泡的角色扮演加熱機制為一個當前有趣的議題。在高頻率時，非線性傳播導致在毫秒之內產生汽化氣泡；在較低的頻率，空化氣泡可能透過黏性逸散、聲學輻射和熱傳導提高溫度。本研究中，旨在探討含氣泡與不含氣泡的仿體燒灼效果。快速多極法(fast multipole method, FMM)用於計算壓力場。溫度場的計算則以壓力場的結果代入生物熱傳導方程式中計算(bio-heat transfer equation, BHTE)。BHTE則是使用商用有限元素分析軟體ANSYS求解。此外，並架設一個研究觀察燒灼效果的必要實驗平台。實驗中變化換能器的趨動頻率及和輸出電功率研究氣泡的影響。於不含氣泡的仿體，紡錘形的焦斑在實驗可觀察並且模擬上可預測。對於含單一氣泡仿體，焦斑在氣泡之前積累並且形成蝌蚪形狀。而微小的空化氣泡在低頻率產生並且在模擬中能合理地被簡化作單一氣泡。我們發現單一氣泡的半徑愈大將導致更大的焦斑。本研究認為空化氣泡和汽化氣泡同樣重要，並且同時提高HIFU的焦斑大小和形狀。A current topic of interest for high intensity focused ultrasound (HIFU) treatments involves the role of bubbles as a heating mechanism. At high amplitudes, nonlinear propagation leads to the generation of boiling bubbles within milliseconds; at lower amplitudes, cavitation bubbles can enhance heating through viscous dissipation, acoustic radiation, and heat conduction.n this study, ablation effects of phantom with and without bubbles were studied. The fast multipole method (FMM) was used to calculate the pressure field. The temperature field was calculated using a bio-heat transfer equation (BHTE) that took the pressure field as the input source. The BHTE was solved using ANSYS. In addition, an experimental platform was set up where critical experiments were conducted to study the ablation effects. Frequency of transducer and output electric power were varied to study the bubble effects. or the cased without bubbles, a cigar-shaped was observed in experiments and predicted in simulation. For the case with a single bubble, lesion was accumulated before the bubble and formed a tadpole-shape. The tiny cavitation bubbles occurred at low frequency could be reasonably simplified as a single bubble in simulation. We found that a larger radius of a single bubble would produce a larger lesion size. We concluded that cavitation bubbles and boiling bubbles share important characteristics and both enhance the lesion size and shape for HIFU.口試委員會審定書 ii 謝 iv 要 vbstract vi 錄 viii目錄 xi目錄 xvi 1 章 緒論 1.1 研究背景 1.2 研究動機與目的 3.3 論文架構 4 2 章 HIFU的基本熱傳原理及模擬理論 5.1 HIFU熱消融(thermal ablation)的機制 5.2 快速多極法（Fast Multipole Method） 6.3 生物熱傳導方程式 12.4 熱劑量計算 14 3 章 實驗的系統設計與準備 15.1 超音波系統架構 15.2 材料準備 20.2.1 超音波介質─去氣水(degassed water) 20.2.2 超波波試體─仿體(phantom) 21.3 溫度量測裝置 27.4 熱傳導係數之量測 28.4.1 穩定外熱源熱傳實驗 29.4.2 穩定內熱源熱傳實驗 32.5 衰減係數之量測 34.6 熱劑量門檻值之量測 36 4 章 燒灼實驗與模擬的方法 39.1 電功率及時間參數的決定 40.2 探討蝌蚪型焦斑形狀之成因 41.3 探討單一氣泡對燒灼效果的影響 43.3.1 單一氣泡燒灼實驗 43.3.2 單一氣泡燒灼模擬 45 5 章 實驗與模擬的結果 48.1 電功率及時間等參數的決定 49.2 探討蝌蚪型焦斑形狀之成因 50.3 探討單一氣泡對燒灼效果的影響 53.3.1 驅動頻率為1.1 MHz時單一氣泡的燒灼效果 55.3.2 驅動頻率為3.17 MHz時單一氣泡的燒灼效果 61.4 成果之討論及建議 68.4.1 焦斑形狀的模擬 68.4.2 電功率與最大壓力的正規化關係 69.4.3 單一氣泡的放大效應 70 6 章 結論 71.1 研究成果與貢獻 71.2 未來研究方向 72考文獻 733563252 bytesapplication/pdfen-US氣泡高能聚焦超音波快速多集法bubblesHIFUFMMthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/187913/1/ntu-98-R95521610-1.pdf