基于AR倒谱法研究人体脾组织微结构的变化

本文利用AR倒谱法对人体正常脾和脾增生组织的回波信号进行了分析,对软组织中散射元的平均间距进行了估计,结果表明：两种脾组织散射元的平均间距明显不同;AR倒谱能有效的反映软组织的微观结构特征,说明AR倒谱是软组织超声散射信号分析与软组织散射元平均间距定征的一种有效方法。     

基于超声散射回波的组织损伤程度监测方法

高强度聚焦超声(HIFU)治疗肿瘤过程中,根据组织损伤程度调整HIFU治疗剂量非常重要.本文从信号处理的角度出发,提出基于超声散射回波能量和声衰减系数并结合BP神经网络监测生物组织损伤程度的方法.将高强度聚焦超声打击新鲜猪肉组织前后获得的散射回波通过A/D转换输入到计算机,对接收到的组织散射回波信号进行预处理,再从中提取出超声散射回波能量和声衰减系数参量信息,比较不同参量对损伤程度的辨识效果.实验结果表明:综合超声散射回波能量和声衰减系数特征并输入BP神经网络,相对于仅使用某种特征参数而言能更好地监测HIFU治疗中生物组织的损伤程度,尤其在组织损伤严重时优势更加明显.     

测量生物组织声衰减的声辐射压力法装置研制

引言 超声波在生物组织媒质中传播时将产生反射、折射、透射、衍射、散射、衰减和非线性等现象,提取和分析这些互作用的信息可以了解生物组织的自身特性。这是现代生物医学超声工程学基础研究的重要内容[1]。研究和测定这些生物组织超声特性参量,一方面为设计超声诊断显象仪、超声治疗仪、超声加热治癌机、超声手术刀等提供设计参数;另一方面也为发展定性定量的超声诊断和治疗提供鉴别判据。因此对于开发新设备和新的医疗方法均有重要意义[2]。 声衰减是声波在生物媒质中传播时的总的声能量损失,与生物组织结构和特性密切相关。国际上已采用…     

基于T矩阵方法的双球体声波散射研究

借鉴已有的T矩阵（Transition matrix）方法,编制了计算不同角度、间距和类型的双球体声散射的Matlab软件,并重点研究了刚性和软性双球体模型的声波散射规律。数值考察结果表明,由于组合的非均匀性,刚-软双球体的正横反向散射强度比刚性和软性双球体的类似情况小,而随双球体间距的变化规律相似;另外,刚-软性双球体端尾方向的反向散射强度平均要比对应的单个球体的散射强度大。     

超声弹性显微镜成像系统开发与应用的初步研究

传统的超声弹性成像技术一般使用1MHz～10MHz的超声波,这一频段超声波的空间分辨率在毫米量级,它不能满足对生物组织中微细结构(如皮肤层,关节软骨等)的研究。文中介绍一套新开发的超声弹性显微镜成像系统,并将其初步应用于对关节软骨和老鼠表皮的成像研究中。该系统由加压系统和背向散射超声显微镜系统两部分组成,其中超声探头频率为50MHz。通过对关节软骨和老鼠表皮的成像实验表明,该系统可以清晰的对生物组织中微细结构成像,研究它们的机械特性。     

高频超声背向散射系数的研究

生物组织的超声散射特性是一切回波超声诊断的物理基础.但是,现有的超声回波诊断仪仅利用了回波中的幅度信息,却丢失了回波在频谱中所携带的大量信息.肝脏组织和淋巴结组织均是动物体极其重要的器官,也是动物体常见的病变器官.应用超声探测肝脏组织开始较早,而且目前对典型的病变已有了比较好的诊断标准,但是对于肝脏弥漫性病变,B超检查时,声像图类似,由于缺乏特异性鉴别诊断较为困难,必须结合临床结果进行综合分析和研究.淋巴结由于其在医学诊断中的特殊的地位而受到医务工作者的极大兴趣.检查淋巴结的变化,可以确定发病的部分及疾病的性质以及疾病发展的程度.但目前用高频诊断淋巴结内部细微病变的报道还不多见,高频段的背向散射系数的结果很少.本文采用高频超声对猪的正常和病变的肝脏组织和淋巴结组织进行了研究,测量了它们的高频背向散射系数,结果表明高频背向散射系数可用于生物组织的定征.     

非均匀软组织声散射模型的研究概况

本文综述了非均匀软组织声散射模型的研究概况及其在超声组织定征中的应用。将声散射模型进行了系统的分类介绍。并对在建立软组织声散射模型中存在的问题以及研究声散射模型的重要意义进行了分析和讨论。     

多盲孔缺陷的超声兰姆波时域拓扑能量成像方法研究

传统超声成像方法受瑞利准则的约束，难以对缺陷间距小于成像分辨率阈值的多缺陷进行成像。提出了一种基于时域拓扑能量的超声兰姆波成像方法，将逆散射拓扑成像方法中的拓扑渐进过程转换成求解直接声场和伴随声场。然后通过将伴随声场进行时间反转，两个声场将具有在缺陷处聚焦，在非缺陷处不聚焦的特性。将直接声场和伴随声场进行融合，以时域拓扑能量值作为像素值进行成像，从而使表征缺陷的精度较高。建立了缺陷间距小于分辨率阈值的多盲孔缺陷有限元模型，通过“一发多收”的方式激发S0模式和采集缺陷散射信号，并进行时域拓扑能量成像。仿真结果表明：对于多盲孔缺陷，时域拓扑能量成像法能够获得比延时叠加法和时间反转成像法更高的分辨率，并且能在缺陷间距小于成像分辨率阈值时进行成像。     

基于超声振动的显微切割技术

为了满足生物组织显微分离的需求,将超声振动引入微切割领域,开发了一套基于超声振动的显微切割系统.在对超声振动微切割理论研究基础上,结合生物组织切割的具体特点,完成了系统总体方案的设计,并对关键技术开展研究,研制了面向生物显微切割技术的执行模块与控制模块,实现了系统的集成.同时,利用该显微切割系统对新生小鼠大脑组织进行超声振动显微切割实验,取得了较理想的切割效果,充分验证了超声振动显微切割技术对生物组织操作的可行性和有效性.     

生物组织微弱散射光的检测装置

首先讨论了生物组织中光传播的高散射特点以有散射光测量方法,建立了组织散射光检测装置,分析了光电池的光电特性及其用于生物散射光检测的可行性。并通过实测给出了使用光电池对人体皮肤、腺瘤等组织的散射光信号的检测结果。     

Simulation of light propagation in bio-tissue under cylindrical boundary condition

Formulas for light propagation in biotissue with cylindrical boundaries are deduced. A model simulating light propagation in one-layered biotissue with a cylindrical boundary is established. Simulation results of the density distribution of absorbed photons are shown when a circularly flat beam is incident on the biotissue. The model can easily be extended to multilayered tissues with cylindrical boundary.     

Fast algorithm to determine optical properties of a turbid medium from time-resolved measurements

After analytical expressions for the time-resolved reflectance are introduced from the diffusion approximation under the three most commonly used boundary conditions, a novel algorithm is demonstrated for determining the reduced scattering and the absorption coefficients from time-resolved reflectance (or backscatter) measurements at two positions on the surface of biotissue. The algorithm is straightforward and fast and involves only some simple mathematical operations, avoiding complicated iterative nonlinear fitting to the time-resolved curve. The derived reduced scattering coefficient is not affected by whatever boundary condition is applied. The algorithm was verified with time-resolved data from the Monte Carlo model. Both a semi-infinite medium and a turbid slab medium were tested. In contrast to the nonlinear fitting method, this algorithm allows both the scattering and the absorption coefficients to be determined to a high accuracy.     

基于数值计算方法的CFRP层板二维细观形貌多孔隙超声散射衰减

针对超声波在含有多孔隙的复合材料中传播时,邻近孔隙超声散射波之间相互作用和散射衰减机制尚未澄清的问题,对孔隙率为7.47%的碳纤维增强复合材料（Carbon Fiber Reinforced Plastic,CFRP）采用时域有限差分方法进行数值计算,对比研究了CFRP层板中不同尺寸范围二维真实形貌孔隙及圆形孔隙对应的超声散射衰减系数。结果表明,对于横向尺寸m≤λ/8、λ/8_s普遍小于真实形貌孔隙的α_s。对于孔隙横向尺寸满足m<2λ/3的情况,大尺寸孔隙以及长条形孔隙的存在,整体上会使超声波散射衰减加重。     

Hyperthermia of cylindrical biotissue samples by microwave electromagnetic radiation

Consideration is given to the interaction of plane and cylindrical electromagnetic waves with layered cylindrical biotissue. Space distributions of the power density of heat loss are calculated and analyzed. The influence of biotissue inhomogeneities (arteries, veins) on electromagnetic heating is evaluated. The results reported can be used for hyperthermia of biological objects in oncology. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 2, pp. 268–272, March–April, 1998.     

The impact of various imaging parameters on ultrasonic displacementand velocity estimates

The accuracy of displacement and velocity data in ultrasonic motion detection systems depends on a combination of ultrasonic imaging parameters. These include magnitude and direction of target motion, target region dimensions, scattering media, ultrasonic frequency of interrogation, digital sampling frequency, and signal type (envelope detected or RF). Because the impact of scattering media in particular has heretofore received little or no attention, we provide experimental results and computer analysis to evaluate the influence of different scattering media on the accuracy of ultrasonic displacement and velocity estimates using porcine liver, porcine muscle, and woolen sea sponge samples. Our experimental results show that for identical target dimensions and displacements, the accuracy of ultrasonic displacement and velocity estimates in porcine muscle samples are substantially higher than in porcine liver samples. Analysis of experimentally derived autocovariance curves for each tissue type indicates that the improvement in accuracy for muscle samples is not, in fact, due to differences in the speckle characteristics for each tissue type. The improvement is attributed to the presence of well-defined and resolvable image structures from muscle and the lack of such resolvable structures in porcine liver tissue. We provide a summary of the factors impacting ultrasonic displacement and velocity measurements, and discuss why and how a combination of one or more imaging parameters affects these measurements     

超声波散射式颗粒测量及其测量结果单值性的分析

提出了一种超声波散射式颗粒测量方法,论述了该技术应用的理论基础,并在详细分析其测量原理基础上,指出了在单频率换能器和单散射角下进行颗粒测量时存在着测量结果多值性的可能。给出了解决这一关键技术问题所采取的可能方案和措施。     

Diffuse ultrasonic backscatter in a two-dimensional domain

The scattering of elastic waves in polycrystalline materials is relevant for ultrasonic materials characterization and nondestructive evaluation (NDE). Diffuse ultrasonic backscatter measurements are used widely to extract the microstructural parameters such as grain size and also to detect flaws in materials. Accurate interpretation of experimental data requires robust scattering models. Line transducers are often used for ultrasonic experiments such that an appropriate model for these two-dimensional problems is needed. Here, a theoretical expression for the temporal diffuse backscatter is derived for such domains under a single-scattering assumption. The result is given in terms of transducer and microstructural parameters. In addition, the problem is examined in terms of numerical simulations using Voronoi polycrystals that are discretized using finite elements in a plane-strain formulation. The material properties of the individual Voronoi cells are chosen according to appropriate material distributions. Such numerical models also allow scattering theories, including the one discussed here, to be examined for well-controlled microstructures. Example numerical results for materials with varying degrees of scattering that are of common interest are presented. The numerical results are compared with the theory developed with good agreement. These results are anticipated to impact ultrasonic NDE of polycrystalline media.     

Anwendung der Kreuzkorrelation mit Ultraschall-CS-Impulsen am Beispiel schallstreuender Werkstoffe

Application of cross correlation to grain scattering materials using controlled ultrasonic signals Investigations are presented which show, that cross correlation analysis (matched filter) enables to increase the flaw detection sensitivity of reflectors in grain scattering materials. The practical application of cross correlation techniques can drastically be simplified by using controlled signals which already include the correlation function. Measurements prove, that the results are in good agreement with the usual, more expensive correlation techniques. The main advantage is, that cross correlation with aid of CS-pulses can be achieved with the same speed as in conventional ultrasonic testing.     

相控聚焦超声与圆孔交互作用的散射特性研究

相较于传统超声检测,相控阵技术的声束聚焦控制能力使得相控超声检测的分辨率、信噪比和灵敏度等性能得到有效提升。但针对相控超声与缺陷的交互作用认识不足,导致目前检测技术无法对缺陷进行准确定性和精确定量。为此,建立了一维线阵相控超声检测圆孔缺陷的有限元模型,重点研究相控聚焦波束与圆孔缺陷交互作用的声场散射特性。结果表明,圆孔散射L模态的能量主要集中于正反射区和正透射区,且在透射区的能量大于反射区的能量,而在与入射声束垂直的方向上能量极其微弱,几乎没有散射能量;散射L模态沿入射方向呈轴对称分布;对于不同直径的圆孔缺陷,直径越大,在相同方向上散射波的能量越大;对于相同直径的圆孔,聚焦波与平面波入射时,散射波的分布规律相同,但聚焦波散射的能量明显高于平面波入射时散射的能量。