本文選題：高強(qiáng)度聚焦超聲 + 非線性聲場(chǎng)�。� 參考：《南京大學(xué)》2014年博士論文

【摘要】：高強(qiáng)度聚焦超聲(High Intensity Focused Ultrasound, HIFU)是一種治療實(shí)體良／惡性腫瘤的非侵入性新興治療技術(shù),焦點(diǎn)的聲強(qiáng)可高達(dá)103W/cm2,能夠在短時(shí)間內(nèi)(秒級(jí))使焦域組織凝固性壞死。為了更好的控制HIFU治療過(guò)程中的臨床效果,需要對(duì)HIFU的非線性聲場(chǎng)進(jìn)行準(zhǔn)確描述。本文首先介紹了HIFU非線性聲場(chǎng)的測(cè)量方法和相關(guān)理論模型,在此基礎(chǔ)上討論了沖擊波產(chǎn)生后,HIFU聲場(chǎng)的定征方法。 針對(duì)大張角強(qiáng)聚焦換能器,本論文提出了頻域-時(shí)域結(jié)合算法計(jì)算其非線性聲場(chǎng)分布的方法。利用橢球坐標(biāo)系非線性方法(SBE)描述聲場(chǎng)分布,在頻域計(jì)算聲場(chǎng)衍射和衰減效應(yīng),在時(shí)域計(jì)算非線性效應(yīng)。該方法計(jì)算結(jié)果與Rayleigh積分及傳統(tǒng)頻域算法計(jì)算結(jié)果吻合的很好,證明了該計(jì)算方法的可靠性。沖擊波產(chǎn)生后,傳統(tǒng)頻域算法計(jì)算時(shí)會(huì)產(chǎn)生明顯的波形振蕩,利用該方法不僅可以有效的避免沖擊波波形振蕩而且還縮短了計(jì)算時(shí)間。 沖擊波產(chǎn)生后,由于其極限條件(強(qiáng)聲壓,寬頻譜,高空間分辨率),直接測(cè)量其聲場(chǎng)分布不僅耗時(shí)且對(duì)測(cè)量設(shè)備的要求較高。本論文提出實(shí)驗(yàn)測(cè)量與理論計(jì)算相結(jié)合的方式定征大張角強(qiáng)聚焦換能器的非線性聲場(chǎng)。首先,忽略換能器封裝等因素,將其視作表面均一振動(dòng)的振子,在線性聲場(chǎng)條件下確定其有效參數(shù)；其次,利用焦點(diǎn)波形二次諧波與基波之比,結(jié)合實(shí)驗(yàn)測(cè)量結(jié)果和模型計(jì)算結(jié)果得到驅(qū)動(dòng)電壓與聲源表面聲壓幅值的關(guān)系；最后,利用SBE模型計(jì)算在任意驅(qū)動(dòng)下的非線性聲場(chǎng)分布。將本方法得到的焦點(diǎn)波形與光纖水聽器測(cè)量結(jié)果做對(duì)比,結(jié)果表明：在較低驅(qū)動(dòng)下,由于非線性效應(yīng)不足以產(chǎn)生足夠高的二次諧波,本方法不能用于描述低驅(qū)動(dòng)下的聲場(chǎng)分布；當(dāng)沖擊波產(chǎn)生后,測(cè)量波形與仿真結(jié)果在峰峰值以及相位上存在差距,兩者的頻譜在50MHz范圍內(nèi)吻合的很好,這說(shuō)明沖擊波產(chǎn)生后,光纖水聽器的測(cè)量波形可能受限于帶寬等原因,與實(shí)際結(jié)果存在一定的差距。本章中提出的方法有助于準(zhǔn)確定征沖擊波產(chǎn)生后的HIFU聲場(chǎng)。 本論文利用實(shí)驗(yàn)測(cè)量與理論計(jì)算相結(jié)合的方法定征HIFU非線性聲場(chǎng),該工作將進(jìn)一步推進(jìn)對(duì)HIFU聲場(chǎng)非線性分布的研究,更加準(zhǔn)確的預(yù)測(cè)超聲在活體組織中的傳播,從而促進(jìn)高強(qiáng)度聚焦超聲在臨床的應(yīng)用。
[Abstract]:High intensity focused ultrasound (HIFU) high Intensity Focused Ultrasound, HIFU) is a new non-invasive treatment technique for solid benign and malignant tumors. The focal sound intensity can be up to 103 W / cm ~ 2 and can cause coagulation necrosis of focal area tissue in a short time (second order). In order to better control the clinical effect of HIFU, it is necessary to accurately describe the nonlinear sound field of HIFU. In this paper, the measurement method and related theoretical model of HIFU nonlinear sound field are introduced, and the method of determining the acoustic field after shock wave is discussed. In this paper, a method for calculating the nonlinear acoustic field distribution of a large angle strong focusing transducer is proposed by combining frequency-domain and time-domain algorithm. The nonlinear method of ellipsoidal coordinate system (SBE) is used to describe the distribution of sound field. The diffraction and attenuation effects of sound field in frequency domain and nonlinear effect in time domain are calculated. The calculated results of this method are in good agreement with the Rayleigh integral and the traditional frequency domain algorithm, which proves the reliability of the method. After the shock wave is produced, the traditional frequency-domain algorithm will produce obvious waveform oscillation, which can not only effectively avoid the shock wave oscillation but also shorten the calculation time. After the shock wave is produced, due to its limit conditions (strong sound pressure, wide frequency spectrum, high spatial resolution), it is not only time consuming to measure the sound field distribution directly, but also the requirement of measuring equipment is high. In this paper, the nonlinear sound field of the strong focus transducer with large angle of tension is determined by combining the experimental measurement with the theoretical calculation. First of all, the transducer packaging is ignored, and it is regarded as a vibrator with homogeneous surface vibration, and its effective parameters are determined under the condition of linear sound field. Secondly, the ratio of the second harmonic to the fundamental wave of the focus waveform is used. The relationship between the driving voltage and the amplitude of sound pressure on the sound source surface is obtained by combining the experimental results with the results of the model calculation. Finally, the nonlinear sound field distribution under arbitrary driving is calculated by using the SBE model. The focus waveform obtained by this method is compared with the measurement results of fiber-optic hydrophone. The results show that the method can not be used to describe the sound field distribution under low driving because the nonlinear effect is not enough to produce high second harmonic. When the shock wave is produced, there is a gap between the measured waveform and the simulation result in peak, peak and phase. The spectrum of the two waves is in good agreement in the range of 50MHz, which indicates that after the shock wave is produced, The measurement waveform of fiber-optic hydrophone may be limited by bandwidth, which is far from the actual results. The method proposed in this chapter is helpful to determine the HIFU sound field after the shock wave is produced. In this paper, the nonlinear acoustic field of HIFU is characterized by the combination of experimental measurement and theoretical calculation. This work will further promote the study of the nonlinear distribution of HIFU sound field, and more accurately predict the propagation of ultrasound in living tissue. So as to promote the clinical application of high intensity focused ultrasound.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：R445.1

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相關(guān)期刊論文 前1條

1 李全義;李發(fā)琪;壽文德;;高強(qiáng)度聚焦超聲(HIFU)的聲場(chǎng)檢測(cè)[J];世界科技研究與發(fā)展;2007年06期

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本文編號(hào)：1913534