脈沖高強(qiáng)度聚焦超聲脈沖參數(shù)與焦點(diǎn)聲壓的關(guān)系研究
發(fā)布時(shí)間：2018-08-27 12:21
【摘要】：高強(qiáng)度聚焦超聲（HighIntensity Focused Ultrasound，HIFU）技術(shù)是一種新興的發(fā)展迅速的非侵入治療技術(shù)，目前已經(jīng)被用于多種腫瘤、非腫瘤疾病的臨床治療中，并取得了很好的療效。HIFU的作用機(jī)制主要是熱效應(yīng)、空化效應(yīng)和機(jī)械效應(yīng)，臨床上主要依靠HIFU的熱效應(yīng)及空化效應(yīng)達(dá)到腫瘤消融的目的。HIFU治療過(guò)程中，空化現(xiàn)象產(chǎn)生的空化氣泡能促使靶區(qū)溫度的進(jìn)一步升高，一定程度上有助于目標(biāo)的消融，但持續(xù)的HIFU輻照過(guò)程中，大量的空化氣泡使聲波在焦前區(qū)發(fā)生散射產(chǎn)生屏蔽作用，熱量隨之在焦前區(qū)累積，使輻照的損傷橫向面積變得更大，同時(shí)損傷位置向換能器方向移動(dòng)，損傷形狀也由分布均勻的“雪茄型”變化為“蝌蚪形”，影響治療的精度。隨著HIFU研究的不斷深入和臨床應(yīng)用，人們發(fā)現(xiàn)低占空比、短 持續(xù)時(shí)間的脈沖高強(qiáng)度聚焦超聲（Pulsed High Intensity FocusedUltrasound,PHIFU）輻照生物組織時(shí)，能夠依靠超聲的機(jī)械效應(yīng)精準(zhǔn)地摧毀靶區(qū)組織而不引起焦區(qū)溫度的顯著上升，PHIFU輻照過(guò)程中由于脈沖持續(xù)時(shí)間短，空化現(xiàn)象未及發(fā)生或者會(huì)有少量空化出現(xiàn)，但少量的空化氣泡不會(huì)對(duì)聲能產(chǎn)生顯著的屏蔽作用，同時(shí)焦點(diǎn)聲壓值能夠瞬時(shí)達(dá)到很高數(shù)值，依靠PHIFU焦區(qū)的高聲壓作用達(dá)到對(duì)摧毀靶區(qū)組織的目的，這對(duì)于提高治療精確性和操作可控性具有潛在優(yōu)勢(shì)。PHIFU輻照過(guò)程中不同脈沖寬度及占空比參數(shù)對(duì)焦點(diǎn)聲壓會(huì)有怎樣的影響、空化現(xiàn)象出現(xiàn)后焦區(qū)聲壓的具體變化，成為目前亟待研究的問(wèn)題。 基于此，本文分析了現(xiàn)有聲場(chǎng)測(cè)量的方法，并對(duì)聲光折射法進(jìn)行了近似，用于測(cè)量脈沖聚焦聲場(chǎng)的焦點(diǎn)聲壓；針對(duì)現(xiàn)有超聲換能器不能方便地進(jìn)行脈沖參數(shù)調(diào)整，，本文提出了一種基于AD9850的可調(diào)脈沖信號(hào)發(fā)射器，可方便進(jìn)行脈沖寬度的調(diào)整，最小脈沖寬度可至0.1ms，在此基礎(chǔ)上測(cè)量了不同脈沖寬度參數(shù)，及脈沖間隔參數(shù)下，焦點(diǎn)聲壓隨輸入電壓的變化數(shù)據(jù)，并與連續(xù)波輻照下進(jìn)行對(duì)比，得出不同的脈沖參數(shù)下，焦點(diǎn)聲壓的變化規(guī)律及焦點(diǎn)的聲壓極值，為后續(xù)臨床實(shí)驗(yàn)及儀器開(kāi)發(fā)提供基礎(chǔ)，結(jié)果顯示在脈沖寬度大于1ms時(shí)，不同的脈沖寬度參數(shù)及脈沖間隔參數(shù)輸入下，焦點(diǎn)聲壓隨電壓變化規(guī)律一致，空化現(xiàn)象出現(xiàn)后焦點(diǎn)聲壓仍會(huì)繼續(xù)升高并達(dá)到極值，空化氣泡大量出現(xiàn)后焦區(qū)聲壓下降，焦區(qū)聲壓極值達(dá)10MPa。
[Abstract]:High intensity focused ultrasound (HighIntensity Focused Ultrasound,HIFU) is a new and rapidly developing non-invasive treatment technique, which has been used in clinical treatment of many kinds of tumor and non-tumor diseases. The effect of cavitation and mechanical effect, mainly depends on the thermal effect and cavitation effect of HIFU to achieve the purpose of tumor ablation. During the treatment of HIFU, cavitation bubbles produced by cavitation can further increase the temperature of target area. To some extent, it is helpful to the ablation of the target, but during the continuous HIFU irradiation, a large number of cavitation bubbles cause the scattering of sound waves in the prefocal region to produce shielding effect, and the heat accumulates in the prefocal region, which makes the transverse area of radiation damage become larger. At the same time, the damage position moved to the direction of transducer, and the damage shape changed from "cigar shape" to "tadpole shape", which affected the treatment accuracy. With the development of HIFU research and clinical application, it has been found that when low duty cycle, short duration of pulsed high-intensity focused ultrasound (Pulsed High Intensity FocusedUltrasound,PHIFU) irradiation of biological tissue, It is possible to destroy the target tissue accurately by the mechanical effect of ultrasound without causing a significant rise in the temperature of the focal area. Due to the short duration of the pulse, cavitation does not occur or a small amount of cavitation occurs during PHIFU irradiation. However, a small amount of cavitation bubbles will not have a significant shielding effect on the sound energy, and the focal sound pressure can reach a very high value at the same time, which depends on the hypersonic pressure in the PHIFU focal region to destroy the target tissue. This has potential advantages for improving treatment accuracy and operational controllability. How do different pulse width and duty cycle parameters affect focal sound pressure during PHIFU irradiation, and the specific changes of sound pressure in focal area after cavitation occur. It has become an urgent problem to be studied at present. Based on this, the existing methods of sound field measurement are analyzed, and the acousto-optic refraction method is approximated to measure the focus sound pressure of the pulse focusing sound field, and the current ultrasonic transducer can not easily adjust the pulse parameters. In this paper, an adjustable pulse signal transmitter based on AD9850 is proposed, which can easily adjust the pulse width. The minimum pulse width can be up to 0.1 ms. on this basis, different pulse width parameters and pulse interval parameters are measured. The variation of focus sound pressure with input voltage is compared with that of continuous wave irradiation. The variation law of focus sound pressure and the sound pressure extremum of focus under different pulse parameters are obtained, which provides the basis for subsequent clinical experiment and instrument development. The results show that when the pulse width is larger than 1ms, under the input of different pulse width parameters and pulse interval parameters, the variation rule of focus sound pressure with voltage is the same, and the focus sound pressure will continue to rise and reach the extreme value after cavitation. The sound pressure of the focal region decreases after the cavitation bubble appears in large numbers, and the maximum of the sound pressure in the focal region reaches 10 MPA.
【學(xué)位授予單位】：重慶醫(yī)科大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2012
【分類(lèi)號(hào)】：R318.0
本文編號(hào)：2207265
[Abstract]:High intensity focused ultrasound (HighIntensity Focused Ultrasound,HIFU) is a new and rapidly developing non-invasive treatment technique, which has been used in clinical treatment of many kinds of tumor and non-tumor diseases. The effect of cavitation and mechanical effect, mainly depends on the thermal effect and cavitation effect of HIFU to achieve the purpose of tumor ablation. During the treatment of HIFU, cavitation bubbles produced by cavitation can further increase the temperature of target area. To some extent, it is helpful to the ablation of the target, but during the continuous HIFU irradiation, a large number of cavitation bubbles cause the scattering of sound waves in the prefocal region to produce shielding effect, and the heat accumulates in the prefocal region, which makes the transverse area of radiation damage become larger. At the same time, the damage position moved to the direction of transducer, and the damage shape changed from "cigar shape" to "tadpole shape", which affected the treatment accuracy. With the development of HIFU research and clinical application, it has been found that when low duty cycle, short duration of pulsed high-intensity focused ultrasound (Pulsed High Intensity FocusedUltrasound,PHIFU) irradiation of biological tissue, It is possible to destroy the target tissue accurately by the mechanical effect of ultrasound without causing a significant rise in the temperature of the focal area. Due to the short duration of the pulse, cavitation does not occur or a small amount of cavitation occurs during PHIFU irradiation. However, a small amount of cavitation bubbles will not have a significant shielding effect on the sound energy, and the focal sound pressure can reach a very high value at the same time, which depends on the hypersonic pressure in the PHIFU focal region to destroy the target tissue. This has potential advantages for improving treatment accuracy and operational controllability. How do different pulse width and duty cycle parameters affect focal sound pressure during PHIFU irradiation, and the specific changes of sound pressure in focal area after cavitation occur. It has become an urgent problem to be studied at present. Based on this, the existing methods of sound field measurement are analyzed, and the acousto-optic refraction method is approximated to measure the focus sound pressure of the pulse focusing sound field, and the current ultrasonic transducer can not easily adjust the pulse parameters. In this paper, an adjustable pulse signal transmitter based on AD9850 is proposed, which can easily adjust the pulse width. The minimum pulse width can be up to 0.1 ms. on this basis, different pulse width parameters and pulse interval parameters are measured. The variation of focus sound pressure with input voltage is compared with that of continuous wave irradiation. The variation law of focus sound pressure and the sound pressure extremum of focus under different pulse parameters are obtained, which provides the basis for subsequent clinical experiment and instrument development. The results show that when the pulse width is larger than 1ms, under the input of different pulse width parameters and pulse interval parameters, the variation rule of focus sound pressure with voltage is the same, and the focus sound pressure will continue to rise and reach the extreme value after cavitation. The sound pressure of the focal region decreases after the cavitation bubble appears in large numbers, and the maximum of the sound pressure in the focal region reaches 10 MPA.
【學(xué)位授予單位】：重慶醫(yī)科大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2012
【分類(lèi)號(hào)】：R318.0
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