【摘要】：高強(qiáng)度聚焦超聲(HIFU)治療目前已經(jīng)被成功地用于多種腫瘤治療之中。其原理是：運(yùn)用超聲換能器將聲能匯聚到生物體腫瘤所在區(qū)域,通過各種效應(yīng),尤其是熱效應(yīng),使該區(qū)域腫瘤細(xì)胞發(fā)生蛋白質(zhì)變性,且盡可能不損傷周邊正常組織,從而達(dá)到治療目的。在臨床應(yīng)中,由于延時(shí)、超調(diào)、振蕩、用時(shí)過長等原因,皮膚燒傷、鈣化、治療不徹底、神經(jīng)損傷等問題時(shí)有出現(xiàn),因此治療目標(biāo)區(qū)域的聲強(qiáng)和溫度控制非常重要。 本文以生物熱傳導(dǎo)模型為基礎(chǔ),對不同換能器在生物組織中產(chǎn)生的聲場和溫度場進(jìn)行了仿真,分析了各種參數(shù)對聲聚焦的影響,并提出了溫度控制方法。所做工作如下： 1.建立生物組織模型,研究了生物熱傳導(dǎo)問題、聚焦聲場的計(jì)算方法和模糊控制有關(guān)理論。 2.研究了凹球面換能器在單層和多層生物媒質(zhì)中產(chǎn)生的聲場,分析了聲源及組織參數(shù)對聲場影響。結(jié)果表明：聲速越大或頻率越低,其最大聲壓值越大、焦距越短；初始聲壓越大或吸收系數(shù)越小,其最大聲壓值越大、焦距幾乎不變；多層媒質(zhì)中某層厚度的變化對焦域最大聲壓值有一定的影響。 3.運(yùn)用偽逆算法研究了相控陣換能器在生物媒質(zhì)中實(shí)現(xiàn)聚焦時(shí)的聲場,分析了不同參數(shù)對聲場特征的影響。結(jié)果表明：換能器陣元間距變大或者陣元寬度變小,焦點(diǎn)處聲壓會變小；換能器頻率不同時(shí),不能采用相同信號進(jìn)行驅(qū)動；生物媒質(zhì)參數(shù)相差較大時(shí),其焦域面積也相差較大；某層的吸收系數(shù)或厚度發(fā)生變化時(shí),其焦點(diǎn)聲壓會受到影響；通過改變陣元驅(qū)動信號,換能器能形成多個(gè)焦點(diǎn),適用于治療大腫瘤。 4.將模糊控制方法用于HIFU治療時(shí)溫度控制,研究了凹球面換能器加熱單層媒質(zhì)和多層媒質(zhì)時(shí)溫度控制效果,及相控陣換能器加熱時(shí)單點(diǎn)和多點(diǎn)溫度控制效果,并與傳統(tǒng)PID控制進(jìn)行了比較。結(jié)果表明模糊控制優(yōu)于傳統(tǒng)PID控制,避免了傳統(tǒng)控制中出現(xiàn)的延時(shí)、超調(diào)、振蕩、用時(shí)過長等問題。 本文做了大量的仿真研究,分析得出了不同參數(shù)對聲場的影響以及聲場優(yōu)化方法；在HIFU加熱治療中提出了模糊控制方法,能有效提高治療的安全性和效率。所做工作對HIFU治療應(yīng)用有重要意義,其結(jié)果對治療劑量選取有參考價(jià)值。
[Abstract]:High intensity focused ultrasound (HIFU) therapy has been successfully used in many kinds of tumor therapy. The principle is that ultrasonic transducers are used to gather sound energy into the area where the tumor is located, and through various effects, especially the thermal effect, the tumor cells in the region undergo protein denaturation without damaging the surrounding normal tissue as much as possible. So as to achieve the purpose of treatment. In clinical practice, due to the causes of delay, overshoot, oscillation, prolonged use, skin burn, calcification, incomplete treatment, nerve injury and so on, it is very important to control the sound intensity and temperature of the target area. Based on the biological heat conduction model, the sound field and temperature field produced by different transducers in biological tissues are simulated, the influence of various parameters on acoustic focusing is analyzed, and a temperature control method is proposed. The work done is as follows: 1. The biological tissue model is established, the biological heat conduction problem, the calculation method of focused sound field and the theory of fuzzy control are studied. 2. The sound field produced by concave spherical transducer in single-layer and multi-layer biological media is studied. The influence of sound source and structure parameters on sound field is analyzed. The results show that the larger the sound velocity or the lower the frequency, the greater the maximum sound pressure and the shorter the focal length, the larger the initial sound pressure or the smaller the absorption coefficient, the greater the maximum sound pressure and the focal length. The variation of the thickness of a certain layer in multilayer medium has a certain influence on the maximum sound pressure in focal region. 3. The sound field of phased array transducer focusing in biological medium is studied by using pseudo-inverse algorithm, and the influence of different parameters on sound field characteristics is analyzed. The results show that the distance between the array elements of the transducer becomes larger or the width of the array becomes smaller, the sound pressure at the focal point becomes smaller, the frequency of the transducer is different, the same signal can not be used to drive the transducer, and the focal area of the transducer varies greatly when the parameters of biological medium differ greatly. When the absorption coefficient or thickness of a certain layer changes, the focus sound pressure will be affected, and by changing the driving signal of the array element, the transducer can form multiple focal points, which is suitable for the treatment of large tumors. 4. The fuzzy control method is applied to the temperature control of HIFU treatment. The effect of temperature control on single layer and multi layer media heated by concave spherical transducer and single and multi point temperature control effect on phase array transducer heating is studied. And compared with the traditional PID control. The results show that the fuzzy control is superior to the traditional PID control, and avoids the problems of delay, overshoot, oscillation and long time in the traditional control. In this paper, the influence of different parameters on the sound field and the sound field optimization method are analyzed, and the fuzzy control method is put forward in the HIFU heating therapy, which can effectively improve the safety and efficiency of the treatment. The results are of great significance to the application of HIFU, and the results are of reference value to the selection of therapeutic dose.
【學(xué)位授予單位】：湖南師范大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TB553;R730.5

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