本文選題：高強度聚焦超聲　切入點：非線性聲場　出處：《南京大學》2012年博士論文　論文類型：學位論文

【摘要】：高強度聚焦超聲(HIFU)技術將聲能量聚焦至靶區(qū),熱消融腫瘤組織而不損傷周圍正常組織。作為一種新興的非侵入式治療腫瘤方法,近年來,HIFU得到了人們極大的關注。本論文的工作主要有兩方面的內容：(1)聲透鏡聚焦換能器的非線性聲傳播模型,(2)HIFU治療中組織損傷形成的掃描方式比較。 聲透鏡式聚焦換能器是常用的聲聚焦方式之一。文中提出了一種計算大張角強聚焦的聲透鏡式聚焦換能器的非線性聲場分布模型。在此模型中,我們使用虛擬球殼式聲源邊界條件來代替聲透鏡邊界條件,虛擬聲源的幾何焦距和孔徑大小先由Snell折射定律確定,再結合Rayleigh積分線性聲場結果微調；然后根據SBE模型,計算聲源的非線性聲場分布。按照此模型計算焦點聲強為7.0kW/cm2時的非線性聲場分布,并與Westervelt方程和KZK方程計算結果相比較；結果表明,此模型能準確的描述焦域附近的非線性聲場分布；對于聲場近場區(qū)域,此模型的計算結果與Rayleigh積分結果以及Westervelt方程結果差異較大。此外,該模型的數(shù)值計算時間約為使用有限差分法計算Westervelt方程所需時間的1/10 HIFU治療較大體積的腫瘤時,換能器需要以一定的掃描模式運動,常用的運動方式有離散序列掃描和連續(xù)掃描兩種。我們將理論建模和實驗結合,比較了這兩種掃描方式下的溫度場和損傷分布。在半透明仿生凝膠中進行實驗研究,聲功率75W,頻率1.12MHz,換能器以不同的掃描速度移動,觀察損傷分布。理論模型中,利用KZK方程描述非線性聲束傳播,利用Pennes傳熱方程描述組織中的溫度變化。理論和實驗結果表明,離散序列掃描模式下,相鄰點間隔增加時,峰值溫度和損傷分布輪廓呈現(xiàn)出鋸齒狀；連續(xù)掃描模式下,峰值溫度和損傷分布的邊界比較光滑；提高掃描速度后,峰值溫度明顯降低。通過控制掃描速度可以控制峰值溫度和損傷分布,這有助于進一步提高HIFU治療效率。此外,和離散序列掃描模式相比,連續(xù)掃描可以在較低的峰值溫度下,達到較高的損傷形成效率(單位時間內形成的損傷面積)。 此外,本論文的其他工作還有：建立了一個聲場、溫度場和微泡相互耦合的數(shù)值模型,以研究焦點溫度達到沸點后,氣化微泡對聲場、溫度場的影響�；赟BE模型,建立強聚焦聲束在多層介質中傳播的非線性模型。 本論文在高強度聚焦超聲的非線性聲場及組織損傷形成方面的理論及實驗研究工作將進一步促進高強度聚焦超聲在臨床上的應用。
[Abstract]:High intensity focused ultrasound (HIFU) technology focuses acoustic energy on the target area, ablation tumor tissue without damaging the surrounding normal tissue. In recent years, great attention has been paid to HIFU. In this paper, there are two main contents: 1) comparing the scanning modes of tissue injury in the treatment of HIFU with the nonlinear acoustic propagation model of lens focusing transducer. The acoustic lens focusing transducer is one of the commonly used acoustic focusing methods. In this paper, a nonlinear sound field distribution model is proposed to calculate the acoustic lens focusing transducer with large angle of tension. The boundary condition of virtual spherical shell sound source is used to replace the boundary condition of acoustic lens. The geometric focal length and aperture of virtual sound source are determined by Snell's refraction law, and then the results of Rayleigh integral linear sound field are fine-tuned, and then according to the SBE model, The nonlinear sound field distribution of the sound source is calculated. The nonlinear sound field distribution is calculated when the focal sound intensity is 7.0 kW / cm ~ 2, and compared with the results of Westervelt equation and KZK equation, the results show that, The model can accurately describe the distribution of nonlinear sound field near focal region, and for the near field of sound field, the results of the model are quite different from the results of Rayleigh integral and Westervelt equation. The numerical calculation time of the model is about 1/10 of the time required to calculate the Westervelt equation by the finite difference method. When HIFU is used to treat large volume tumors, the transducer needs to move in a certain scanning mode. There are two common motion modes: discrete sequence scanning and continuous scanning. The temperature field and damage distribution of these two scanning modes were compared. The experimental study was carried out in a translucent bionic gel. The acoustic power was 75W, the frequency was 1.12MHz, the transducer moved at different scanning speeds, and the damage distribution was observed. The KZK equation is used to describe the nonlinear acoustic beam propagation and the Pennes heat transfer equation is used to describe the temperature change in the tissue. The theoretical and experimental results show that when the interval between adjacent points increases in the discrete sequence scanning mode, The contour of peak temperature and damage distribution is serrated. In continuous scanning mode, the boundary between peak temperature and damage distribution is smooth. The peak temperature and damage distribution can be controlled by controlling the scanning speed, which is helpful to further improve the therapeutic efficiency of HIFU. In addition, compared with discrete sequence scanning mode, continuous scanning can be used at lower peak temperature. To achieve higher damage formation efficiency (damage area per unit time). In addition, the other work of this paper is to establish a numerical model of the coupling of sound field, temperature field and microbubble to study the effect of vaporizing microbubble on sound field and temperature field after the focal temperature reaches boiling point. A nonlinear model for the propagation of a strong focused sound beam in a multilayer medium is established. The theoretical and experimental research on the nonlinear sound field and tissue damage of high intensity focused ultrasound (HIFU) will further promote the clinical application of HIFU.
【學位授予單位】：南京大學
【學位級別】：博士
【學位授予年份】：2012
【分類號】：R310

【共引文獻】

中國博士學位論文全文數(shù)據庫 前1條

1 劉全宏;超聲激活血卟啉抗腫瘤的細胞學研究[D];陜西師范大學;2003年

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本文編號：1586873