声人工结构增强医学超声换能器聚焦性能的研究

发布时间：2018-03-11 04:36

本文选题：声人工结构　切入点：倏逝波　出处：《南京大学》2016年博士论文　论文类型：学位论文

【摘要】：医学超声的迅速发展对声学设备提出了更高的要求,聚焦换能器作为医学超声中的一种重要元件,由于其工作原理和性能的限制,已难以满足医学超声发展的需求。声人工结构因其具有普通材料无法实现的功能、可产生奇特的物理效应而得到人们的广泛关注。随着声人工结构研究的蓬勃发展,其在生物医学超声中的应用也受到学术界的极大关注。本论文主要研究声人工结构材料中特殊的物理效应在医疗聚焦超声方面的潜在应用,主要内容包括：(1)亚波长聚焦,(2)艾里声束聚焦,(3)声超常聚焦透镜。传统的聚焦换能器,受到衍射极限的限制无法获得半波长以下尺寸的焦点,影响了超声治疗的治疗精度。一般而言,物体的散射声波中包括行波与倏逝波,其中倏逝波的幅值会随着传播距离呈指数衰减。传统声学成像技术中接收换能器无法获得倏逝波的信息。人们在研究声人工结构时发现其对倏逝波的放大效应,在此基础上实现了突破衍射极限的超分辨率成像。本论文以声人工结构的倏逝波放大效应为基础,设计了一种多通道结构,实现了声亚波长聚焦。该结构在提高医学超声成像质量、高强度聚焦超声(HIFU)青细聚焦等方面有着潜在的应用。在使用HIFU治疗胸腹部的组织时,肋骨常在声传播路径上,会对治疗效果造成极大影响,为了能够使声束弯曲绕开骨骼治疗骨后组织,同时也为了进一步对聚焦声束进行精确操控,我们研究了艾里声束的实现方法。作为一类典型的弯曲无衍射束,艾里束在医学超声的应用中有着重要的意义。然而由于艾里函数的复杂性,以及工艺制造水平限制,使用传统的方式激发艾里声束存在着极大的困难。声人工结构中的声超表面结构具有良好的调控声波相位的能力,因此我们通过在传统活塞振子表面设计与艾里函数相位对应的声人工结构,对波阵面的相位进行调控,通过数值模拟阐明了实现了艾里声束的方法。相对于其他的方法,我们所提出的方法具有简单、易实现的优势。最后,本论文探讨了利用一类特殊声透镜对聚焦效果进行优化的方法。声透镜式聚焦换能器因其应用简便、制作简单,是最常用的聚焦器件之一。本论文提出,在传统的聚焦声透镜的球形表面,根据声准直理论设计人工结构形成声超常透镜。数值模拟和实验测量结果均表明,该透镜能够有效地改善聚焦性能,实现旁瓣抑制,因而对于提高HIFU治疗的安全性和治疗精度有潜在的应用价值。声人工结构可用于产生奇特的物理效应,但更重要的问题是将其与实际应用相结合。本论文所提提出的三类结构对超声诊断及治疗有重要的应用价值,例如：利用亚波长聚焦透镜可实现亚波长超声成像,利用非衍射艾里声束聚焦和声超常透镜可以提高超声治疗的安全性。本论文的研究工作对于推动医学超声设备的发展有着积极的作用,另一方面,也为声人工结构的研究开辟了新的应用领域。
[Abstract]:The rapid development of medical ultrasound has put forward higher requirements on the acoustic equipment, as an important element focused transducer in medical ultrasound, because of its working principle and performance constraints, has been difficult to meet the needs of the development of medical ultrasound. The sound of artificial structure because of its common materials can not be achieved, can produce peculiar physical effects get people's attention. With the rapid development of artificial structure sound, its application in biomedical ultrasound has attracted much attention in academic circles. The potential application of special physical effects, this thesis mainly studies the sound artificial structural materials in medical ultrasound aspects, the main contents include: (1) subwavelength focusing. (2) AI Lisheng focused beam (3) abnormal sound focusing lens. The focal point of the traditional transducer, unable to obtain the half wavelength size is below the diffraction limit, the effect of ultrasound The treatment of accuracy. In general, the scattered wave objects include traveling wave and evanescent wave, the amplitude of the evanescent wave will decrease exponentially with propagation distance. The traditional acoustic imaging technology in receiving transducer cannot obtain the evanescent wave information. It has been found on the amplification of the evanescent wave effect in the study of acoustic artificial structure when implemented on the basis of super-resolution imaging beyond the diffraction limit. In this paper, the structure of artificial acoustic evanescent wave amplification effect as the basis for the design of a multi-channel structure, to achieve sound subwavelength focusing. The structure in the improvement of medical ultrasonic imaging quality, high intensity focused ultrasound (HIFU) with the potential application of green fine focusing etc. in the treatment of thoracic and abdominal HIFU tissue, ribs often in the sound path, will cause a great impact on the treatment effect, in order to make the beam bending around the bone after bone treatment group Fabric, at the same time in order to further accurate manipulation of the focused beam, we study the implementation method of AI Lisheng beam. As a kind of typical bending non diffraction beam and Airy beam in the application of medical ultrasound has important significance. However, due to the complexity of the Airy function, and level of manufacturing process, the use of the traditional way to stimulate the AI Lisheng beam there are great difficulties. The sound of artificial structure in the acoustic structure has good control over the surface acoustic wave phase ability, so we passed in a traditional piston vibrator surface design and Airy function phase corresponding to the sound of artificial structures, the regulation of wavefront phase, through the numerical simulation to illustrate the realization method of AI Lisheng beam. Compared with other methods, the proposed method is simple and easy to realize the advantages. Finally, this paper discusses on the focus by using a special class of acoustic lens Optimization method. The acoustic lens type focusing transducer because of its simple application, simple production, is one of the most commonly used focusing device. In this paper, the spherical surface focusing lens of the traditional theory, based on the sound design of artificial collimation structure formed abnormal sound lens. Numerical simulation and experiment results show that the lens can effectively improve the focusing performance, achieve sidelobe suppression, thus to have potential application value to improve the safety and accuracy of treatment HIFU treatment. The sound of artificial structures can be used to generate physical effect peculiar, but the more important question is to combine them with practical application. This paper proposed three kinds of structure of the application the value of ultrasonography in the diagnosis and treatment for example: the use of subwavelength focusing lens can realize subwavelength imaging, can improve the utilization of non diffraction beam focusing lens and extraordinary Lisheng AI The safety of ultrasound treatment is of great importance in promoting the development of medical ultrasound equipment. On the other hand, it has opened up a new application field for the research of acoustic artificial structure.

【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TB552

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