基于微納米顆粒的光聲多普勒微循環(huán)流速測(cè)量
發(fā)布時(shí)間：2018-08-07 15:09
【摘要】：人體的微循環(huán)系統(tǒng)主要在微血管，微血管也叫毛細(xì)血管，是血液與周?chē)M織進(jìn)行物質(zhì)交換的場(chǎng)所，而流速是表征血管性能的一個(gè)重要參數(shù)，微血管或周?chē)M織的病變會(huì)導(dǎo)致血流發(fā)生變化。微血管的流速測(cè)量和成像對(duì)于心腦血管等疾病的預(yù)防及治療有著非常重要的作用。 目前的血液流速測(cè)量主要是利用多普勒技術(shù)，主要包括超聲多普勒和激光多普勒流速測(cè)量。超聲多普勒測(cè)速的原理是利用流體中運(yùn)動(dòng)微粒散射聲波的多普勒頻移來(lái)獲得液體流速信息，由于人體內(nèi)組織的緩慢運(yùn)動(dòng)，在測(cè)量低流速時(shí)，獲得的多普勒信號(hào)不只來(lái)自于流動(dòng)的微粒還有管壁的影響，因此在低流速下超聲多普勒的測(cè)量受到很大制約；激光多普勒的原理與超聲多普勒相似，也是利用了運(yùn)動(dòng)微粒的光散射，雖然它能夠測(cè)得較低的流速，但是測(cè)量深度有限，并且不能獲得流速的方向信息。光聲多普勒技術(shù)很好的解決了這一問(wèn)題，它兼有聲學(xué)測(cè)量和光學(xué)測(cè)量的優(yōu)點(diǎn)，有很高的光學(xué)對(duì)比度和較低的背景噪聲。 本課題根據(jù)光聲多普勒頻移與流速的線性關(guān)系，設(shè)計(jì)了一套以鎖相放大器為核心的低流速測(cè)量系統(tǒng)，通過(guò)光聲多普勒信號(hào)與參考信號(hào)混頻運(yùn)算得到光聲多普勒頻移信號(hào)，然后對(duì)其進(jìn)行快速傅里葉變換得到多普勒頻移，進(jìn)而計(jì)算出平均流速；為了驗(yàn)證流速與超聲探頭的夾角（多普勒角度）對(duì)多普勒頻移的影響，以豐富和補(bǔ)充光聲多普勒理論，對(duì)原有的實(shí)驗(yàn)系統(tǒng)做了改進(jìn)，，利用步進(jìn)電機(jī)帶動(dòng)超聲探頭的旋轉(zhuǎn)，完成了對(duì)多普勒角度的掃描。 實(shí)驗(yàn)結(jié)果表明，多普勒角度的余弦值與多普勒頻移呈線性關(guān)系，本文提出的方法適用于低流速的測(cè)量，相比于其它多普勒流速測(cè)量技術(shù)，不但有較好的測(cè)量準(zhǔn)確性，還能判斷流速方向，并討論了多普勒角度與多普勒頻移的關(guān)系，作為一種新技術(shù)它可能為微血管低流速測(cè)量提出了一種新的無(wú)創(chuàng)測(cè)量手段。
[Abstract]:The microcirculation system of the human body is mainly in the microvessels, which are also called capillaries. They are the places where the blood exchanges substances with the surrounding tissues, and the velocity of flow is an important parameter to characterize the performance of blood vessels. Changes in blood flow can result from changes in microvessels or surrounding tissues. Microvascular velocity measurement and imaging play an important role in the prevention and treatment of cardiovascular and cerebrovascular diseases. At present, Doppler technique is mainly used to measure blood velocity, including ultrasonic Doppler and laser Doppler velocity measurement. The principle of ultrasonic Doppler velocimetry is to obtain the velocity information of liquid by Doppler frequency shift of moving particles scattering sound wave in fluid. Because of the slow movement of human body tissue, when measuring low velocity of velocity, The Doppler signal is obtained not only from the flowing particles but also from the tube wall, so the measurement of ultrasonic Doppler at low velocity is greatly restricted; the principle of laser Doppler is similar to that of ultrasonic Doppler. The light scattering of moving particles is also used. Although it can measure low velocity, the depth of measurement is limited, and the direction information of velocity can not be obtained. Photoacoustic Doppler technique solves this problem very well. It has the advantages of both acoustic measurement and optical measurement. It has high optical contrast and low background noise. According to the linear relationship between photoacoustic Doppler frequency shift and velocity, a low velocity measurement system with phase-locked amplifier as the core is designed in this paper. The photoacoustic Doppler frequency shift signal is obtained by mixing the photoacoustic Doppler signal with the reference signal. Then the Doppler frequency shift is obtained by fast Fourier transform, and the average velocity is calculated. In order to verify the influence of the angle between the velocity and the ultrasonic probe (Doppler angle) on the Doppler frequency shift, the photoacoustic Doppler theory is enriched and supplemented. The original experimental system was improved and the ultrasonic probe was rotated by stepper motor, and the Doppler angle was scanned. The experimental results show that there is a linear relationship between the Doppler angle cosine value and the Doppler frequency shift. The proposed method is suitable for low velocity measurement. Compared with other Doppler velocity measurement techniques, the proposed method not only has a good accuracy. The relationship between Doppler angle and Doppler frequency shift is also discussed. As a new technique, it may provide a new non-invasive method for microvascular low velocity measurement.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2012
【分類號(hào)】：R318.6
[Abstract]:The microcirculation system of the human body is mainly in the microvessels, which are also called capillaries. They are the places where the blood exchanges substances with the surrounding tissues, and the velocity of flow is an important parameter to characterize the performance of blood vessels. Changes in blood flow can result from changes in microvessels or surrounding tissues. Microvascular velocity measurement and imaging play an important role in the prevention and treatment of cardiovascular and cerebrovascular diseases. At present, Doppler technique is mainly used to measure blood velocity, including ultrasonic Doppler and laser Doppler velocity measurement. The principle of ultrasonic Doppler velocimetry is to obtain the velocity information of liquid by Doppler frequency shift of moving particles scattering sound wave in fluid. Because of the slow movement of human body tissue, when measuring low velocity of velocity, The Doppler signal is obtained not only from the flowing particles but also from the tube wall, so the measurement of ultrasonic Doppler at low velocity is greatly restricted; the principle of laser Doppler is similar to that of ultrasonic Doppler. The light scattering of moving particles is also used. Although it can measure low velocity, the depth of measurement is limited, and the direction information of velocity can not be obtained. Photoacoustic Doppler technique solves this problem very well. It has the advantages of both acoustic measurement and optical measurement. It has high optical contrast and low background noise. According to the linear relationship between photoacoustic Doppler frequency shift and velocity, a low velocity measurement system with phase-locked amplifier as the core is designed in this paper. The photoacoustic Doppler frequency shift signal is obtained by mixing the photoacoustic Doppler signal with the reference signal. Then the Doppler frequency shift is obtained by fast Fourier transform, and the average velocity is calculated. In order to verify the influence of the angle between the velocity and the ultrasonic probe (Doppler angle) on the Doppler frequency shift, the photoacoustic Doppler theory is enriched and supplemented. The original experimental system was improved and the ultrasonic probe was rotated by stepper motor, and the Doppler angle was scanned. The experimental results show that there is a linear relationship between the Doppler angle cosine value and the Doppler frequency shift. The proposed method is suitable for low velocity measurement. Compared with other Doppler velocity measurement techniques, the proposed method not only has a good accuracy. The relationship between Doppler angle and Doppler frequency shift is also discussed. As a new technique, it may provide a new non-invasive method for microvascular low velocity measurement.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2012
【分類號(hào)】：R318.6
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