基于热效应的深度光声成像研究

发布时间：2018-05-30 02:17

本文选题：热效应 + HIFU　；参考：《电子科技大学》2015年硕士论文

【摘要】：光声成像(Photoacoustic Tomography,PAT)是指以激光作为激发源,利用目标介质内部光吸收差异,进而产生不同频率的超声波,通过超声探测器接收,采用图像重建算法进行图像重建的成像方法。因此光声成像方法兼具超声波成像的高分辨率和光学成像的高对比度优势。然而光声成像方法的成像质量仍有待加强,临床尚不能满足生物组织的深层次的高分辨率成像。虽然光声成像模式开辟了避免光散射效应的有别于纯光学成像的新的成像方法,但光声信号尤其是高频或组织深处的光声信号常因强烈的衰减而难以被探测,这限制了光声成像对组织深处的高质量成像。因此本文提出一种新型的基于热效应的光声成像方式。利用外界激励源(激光,聚焦超声或者微波)加热目标,产生一个有别于周围温度的区域,温度的差异导致声速的差异,从而形成一个热致声透镜。再利用透镜的聚焦作用,获取深层次的光声信号,从而达到加深成像深度和改善成像质量的目的。本论文首次将激励源产生的热效应嫁接于光声成像,具体内容如下:1.分析了光声成像技术的优点和目前发展中面临的问题,拣选了应对所面临的问题的现有的办法,重点提出了本文解决这些问题的办法以及本文的研究意义。2.梳理了光声成像技术理论,重点分析了光声信号产生的物理过程,对影响光声成像质量的因素做了细致的研究。3.从理论和实验上分析了和验证了热效应的产生。重点分析了高强度聚焦超声(HIFU,High intensity focus ultrasound)产生的热效应。理论部分主要分析了热效应物理过程以及热效应对目标介质物理性质尤其是声学性质的影响;实验部分着重分析和验证了高强度聚焦超声照射目标介质时所产生热效应的情况,即所产生焦斑形状大小以及焦斑对声束的聚焦能力。4.对基于热效应的深度光声成像技术进行了实验研究。搭建了光声成像实验的硬件系统,开展了光声成像实验、基于热效应的光声成像实验,实验验证并证实了热效应对光声成像的改善作用。
[Abstract]:Photoacoustic Tomography (Pat) is an imaging method which uses laser as the source of excitation, uses the difference of light absorption in the target medium, and then produces ultrasonic waves of different frequencies, receives by ultrasonic detector, and uses image reconstruction algorithm to reconstruct the image. Therefore, photoacoustic imaging has the advantages of high resolution of ultrasonic imaging and high contrast of optical imaging. However, the imaging quality of photoacoustic imaging still needs to be improved, and the clinical application can not meet the high resolution imaging of biological tissue. Although photoacoustic imaging modes have opened up new imaging methods different from pure optical imaging that avoid light scattering effects, photoacoustic signals, especially those in high frequency or deep tissue, are often difficult to detect because of strong attenuation. This limits the quality of photoacoustic imaging in deep tissue. Therefore, a new photoacoustic imaging method based on thermal effect is proposed. Using external excitation sources (laser, focused ultrasound or microwave) to heat the target, a region different from the surrounding temperature is produced. The difference of temperature leads to the difference of sound velocity, thus forming a thermoacoustic lens. Then, the deep photoacoustic signal is obtained by focusing the lens, so as to deepen the imaging depth and improve the imaging quality. In this paper, the thermal effect of excitation source is grafted into photoacoustic imaging for the first time, as follows: 1. This paper analyzes the advantages of photoacoustic imaging technology and the problems in its development, selects the existing methods to deal with the problems, and puts forward the methods to solve these problems and the significance of the research in this paper. The theory of photoacoustic imaging technology is combed, the physical process of photoacoustic signal generation is analyzed emphatically, and the factors influencing the quality of photoacoustic imaging are studied in detail. The thermal effect is analyzed and verified theoretically and experimentally. The thermal effect of high intensity focused ultrasound (HIFU) high intensity focus ultrasound) was analyzed. The theoretical part mainly analyzes the physical process of thermal effect and the influence of thermal effect on the physical properties of target medium, especially the acoustic properties. That is, the shape and size of the focal spot and the focusing ability of the focal spot to the sound beam. 4. The depth photoacoustic imaging technology based on thermal effect is studied experimentally. The hardware system of the photoacoustic imaging experiment is built, the photoacoustic imaging experiment is carried out, and the photoacoustic imaging experiment based on the thermal effect is carried out, which verifies and verifies the improvement effect of the thermal effect on the photoacoustic imaging.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TP391.41;TN249

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