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Feature analysis of Doppler ultrasound signals obtained from mammalian arteries.

机译:从哺乳动物动脉获得的多普勒超声信号的特征分析。

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摘要

In this research, we have derived a closed-form solution for the axial and radial velocities of a Newtonian incompressible fluid flowing under a pulsatile pressure gradient through nonuniform, cylindrical, rigid and elastic tubes. The nonuniformity was achieved by choosing an obstruction having the shape of a {dollar}beta{dollar}-function on the inner surface of the tube. The theory thus developed was applied to mathematically model the flow of blood through arteries with fat and cholesterol deposits on their inner surface. The advantage of using a {dollar}beta{dollar}-function to model the internal obstruction, was that it could be skewed to either side so as to more realistically approximate the various shapes and sizes of plaque deposits in diseased arteries.; From the mathematical model we simulated a Doppler signal having the same basic characteristics of amplitude and frequency modulation as an experimental Doppler ultrasound signal that is obtained from diagnostic ultrasound equipment used in hospitals. We used a Diasonics ultrasound scanner to obtain the experimental Doppler signals from the carotid arteries of humans, as well as from a laboratory model that utilized polyurethane and silicone tubes having varying degrees of elasticity.; Several signal processing methods were applied to both the simulated and experimental Doppler signals to study the effect of atherosclerosis on hemodynamics. These methods included the exponential time-frequency distribution and the wavelet transform. In addition, we also used the cepstrum coefficients, and the energy and autocorrelation functions. The goal was to determine the degree (% reduction of lumen diameter), position (anterior, posterior, medial or lateral), and the shape of atherosclerotic plaque in human carotid arteries. Using our fluid flow model, it was possible to change any of its parameters (for example, the shape or size of the obstruction, or the elasticity of the vessel wall) and note the corresponding effect on any feature extracted from the simulated Doppler signal. Whilst other researchers have focused primarily on determining the presence of the plaque and on the degree of reduction of lumen diameter, we have also aimed at determining the plaque shape and its position.; The results of our simulations using the mathematical model are presented. We monitored the changes in the velocity profiles of the fluid as a function of time, as it flowed through the obstruction. We also noted that the propagation velocity of the pressure pulse wave in an elastic tube decreased, whereas the attenuation per wavelength increased, as the wave traveled from the proximal end of the obstruction to the location in the region of the obstruction where the tube diameter was minimum. Cepstral analysis was useful in determining the degree of blockade by measuring the position, in feature space, of the observed feature with respect to that of clusters of features of normal and stenotic arteries of known degrees of obstruction. Using the autocorrelation function we had limited success in determining the location of the plaque. However, it proved to be very useful in determining the plaque position. The exponential distribution was used to monitor the changes in the frequency content of the Doppler signal during a complete pressure cycle. By measuring the ratio of energies of the wavelet coefficients corresponding to various subbands, the wavelet transform proved effective in determining the approximate shape of the obstruction. (Abstract shortened by UMI.)
机译:在这项研究中,我们导出了牛顿不可压缩流体在脉动压力梯度下通过不均匀,圆柱形,刚性和弹性管的轴向和径向速度的封闭形式的解决方案。通过选择在管的内表面上具有{美元}β{美元}功能的形状的障碍物来实现不均匀性。如此发展的理论被用于数学模拟动脉内壁上沉积有脂肪和胆固醇的血液流动。使用{dollar} beta {dollar}函数对内部梗阻进行建模的优势在于,它可以偏向任一侧,以便更实际地估算患病动脉中斑块沉积的各种形状和大小。从数学模型中,我们模拟了具有与从医院中使用的诊断超声设备获得的实验多普勒超声信号相同的振幅和频率调制基本特性的多普勒信号。我们使用Diasonics超声波扫描仪从人的颈动脉以及使用具有不同弹性程度的聚氨酯和硅胶管的实验室模型中获得实验性多普勒信号。将几种信号处理方法应用于模拟和实验多普勒信号,以研究动脉粥样硬化对血液动力学的影响。这些方法包括指数时频分布和小波变换。此外,我们还使用了倒谱系数以及能量和自相关函数。目的是确定人颈动脉的程度(管腔直径缩小的百分比),位置(前,后,内侧或外侧)和动脉粥样硬化斑块的形状。使用我们的流体流动模型,可以更改其任何参数(例如,阻塞物的形状或大小或血管壁的弹性),并注意对从模拟多普勒信号提取的任何特征的相应影响。虽然其他研究人员主要致力于确定斑块的存在和管腔直径的减小程度,但我们也旨在确定斑块的形状及其位置。给出了我们使用数学模型进行仿真的结果。当流体流过阻塞物时,我们监测了流体速度曲线随时间的变化。我们还注意到,压力波在弹性管中的传播速度降低,而每波长的衰减则增加,因为该波从阻塞的近端传播到阻塞区域中管直径为最低。相对于已知阻塞程度的正常和狭窄动脉的特征簇,倒谱分析可用于通过测量观察到的特征在特征空间中的位置来确定阻塞程度。使用自相关函数,我们无法成功地确定斑块的位置。然而,事实证明,它对确定菌斑位置非常有用。指数分布用于监控整个压力周期内多普勒信号频率成分的变化。通过测量对应于各个子带的小波系数的能量比,小波变换被证明对于确定障碍物的近似形状是有效的。 (摘要由UMI缩短。)

著录项

  • 作者

    Chugani, Mahesh Lakhi.;

  • 作者单位

    Rensselaer Polytechnic Institute.;

  • 授予单位 Rensselaer Polytechnic Institute.;
  • 学科 Engineering Electronics and Electrical.; Engineering Biomedical.; Mathematics.
  • 学位 Ph.D.
  • 年度 1996
  • 页码 250 p.
  • 总页数 250
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 无线电电子学、电信技术;生物医学工程;数学;
  • 关键词

  • 入库时间 2022-08-17 11:49:20

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