合成波束多普勒血流滚动频谱信息处理方法及研究

本文针对用相控阵超声换能器合成波束提取和处理多谱勒血流信息的原理和方法进行了较深入的讨论和研究。相应于所获得血流信息的要求，重点介绍了进行多普勒血流实时滚动频谱及功率谱分析的特殊方法。通过谱分析结果与Ｂ型二维图像和Ｍ型心动图的同步显示可以获得关于心脏及血管血流的动态分析，血流途径、方向和性质、血容量及血流速度等信息，从而可为心脏瓣膜及血管疾病的诊断提供重要依据，使超声检查心疾病的手段深入到血液动力     

多普勒血流信号最大频率曲线的特征分析及应用

文章主要研究从超声多普勒血流信号的最大频率曲线中提取特征值,并用于临床血管疾病诊断的方法。先利用短时傅里叶变换分析采样所得的音频多普勒血流信号,接着用百分比法得到信号的最大频率曲线,然后提取最大频率曲线频谱各峰值的比作为特征值,并将它们用于血管疾病的诊断。通过对颈动脉多普勒血流信号的临床分析表明：此方法比传统的声谱参数法有更高的诊断准确性。     

冠脉内超声多普勒血流信号的极点特征

研究冠脉内超卢多普勒血流信号的极点特征，期望为微循环障碍等缺血性心脏病的诊断提供客观指标。先对冠脉内超声多普勒血流信号分段建立自回归滑动平均（Auto-regressive＆moving-average，即ARMA）模型，获取一个心动用期信号的极点分布，计算极点分布的特征参数。通过分析18例冠脉内超声多普勒血流信号，得出若干个对冠脉微循环障碍敏感的特征参数。结果表明：冠脉内超声多普勒血流信号的极点特征参数，可以一定程度反映冠脉循环的状况。     

超声经颅多普勒血流分析仪校准方法探讨

本文探讨了超声经颅多普勒血流分析仪血流速度的校准方法,并分析了3台不同厂家的超声经颅多普勒血流分析仪血流速度的重复性。创新了探测深度的校准方法,以产品标准或使用手册中公布的最大深度为标准要求,分析血流速度参考值和测量值之间的关系,最终确定探测深度。     

利用超声多普勒技术测量低速血流

利用常规的多普勒系统较难进行低速血流的测量，本文在讨论了常规的多普勒系统的局限后，就一种可测量低速血流的超声多普勒技术的原理，方法进行讨论，并通过计算机模拟实验实现了这种方法。     

利用超声多普勒技术检测血栓

血栓检测对早期诊断血管疾病有十分重要的意义，超声多普勒技术是一种常用的血栓无损检测方法。当血栓通过超声多普勒仪器的采样容积时，会引起超声多普勒信号功率的瞬时增强，因此可以直接根据超声多普勒信号时域波形幅度的变化来检测血检。但是由于系统可能存在着干扰，这种基本的检测方法有着较大的局限。为了克服这一缺陷，可以利用信号处理的新理论，通过提取血栓信号的敏感特征参数，来达到提高血栓自动检测准确性的目的。     

多波束条带测深系统中正交信号的获取技术

本文针对多波束条带测深系统，提出了一种优化的数字希尔伯特（Ｈｉｌｂｅｒｔ）变换方法，来获取幅度和相位严格平衡的正交信号。给出了理论分析过程和实时产生多路正交信号的基于流水线操作的硬件实现结构。湖上实验表明了这种方法的有效性以及工程实现的简单可靠性。     

彩色多普勒超声诊断仪血流部分检测方法

文章对彩色多普勒超声诊断仪的重要性能指标——血流检测进行了探讨,详细介绍了检测模体结构、血流检测的操作步骤以及常见故障的排除方法,对影像诊断中,采用彩色多普勒超声诊断仪检测血流具有一定的指导意义和参考价值。     

结合横向振荡和空间正交的向量血流速度测量

传统的彩色多普勒成像只能测量与超声波束平行的血流速度分量,且依赖于超声波束与血管之间的夹角。超声向量血流成像是一种更加先进的血流成像技术,该方法可以直接获得血流速度的实际大小和方向,因此不依赖于超声波束与血管之间的夹角。本文从向量血流测量方法之一的横向声场法入手,简要概括了横向振荡(Transverse Os‐cillation, TO)法和空间正交(Spatial Quadrature, SQ)法两种方法的基本原理、成像过程及各自的优缺点,并提出了一种互相结合的方法,即奇偶振荡法(Odd Even Oscillation, OEO),该方法利用 SQ法快速进行波束合成,利用 TO法计算最终的速度矢量,克服了 TO法和 SQ法各自的缺点,能够有效解决 TO法成像计算量大以及 SQ法出现混叠和对噪声灵敏度高的问题。     

血栓多普勒信号的多参数提取及分类

血栓的准确检测可以用于早期脑血管疾病的诊断，超声多普勒是一种无损的血栓检测技术。文章使用三种信号处理方法：传统的声谱分析法、小波分析法、renyi信息量分析法对血栓多普勒信号进行分析，提取出相应的特征参数，然后对敏感的特征参数采用反向传输(Back-Propagation，简称BP)神经网络进行分类，建立起血栓、干扰噪声和正常血流信号的自动判别系统。通过对300例仿真多普勒信号和163例临床采集的大脑中动脉多普勒信号进行分析，结果表明：本文建立的系统对血栓的检测率高于传统的方法，有望可用于血栓多普勒信号的自动检测。     

Denoising quadrature Doppler signals from bi-directional flow using the wavelet frame

A novel approach was proposed to denoise quadrature Doppler signals from bi-directional blood flow using the wavelet frame and a soft-thresholding algorithm. A direction separation step was carried out first to avoid the phase distortion of quadrature Doppler signals, which is induced from the nonlinear, soft-thresholding processing. Then real parts of separated complex signals from the unidirectional flow were denoised independently. The quadrature Doppler signals from the bi-directional flow were reconstructed from the denoised separated signals. The approach has been applied to the simulated Doppler signals from a femoral artery. It is concluded from the experimental results that this method is practical for denoising quadrature Doppler signals.     

单边狭窄血管中超声多普勒信号的仿真研究

超声多普勒技术作为一种无损检测手段被广泛应用于血管狭窄的检测。以往的血管狭窄仿真信号的研究仅限于双边狭窄的对称情况,文章提出了一种单边狭窄血管中超声多普勒信号的仿真方法。首先用有限元分析方法(FEM)计算出狭窄血管中血流流速场分布情况,然后用总体分布非参数估计法计算出超声多普勒信号的功率谱密度(PSD),再用余弦叠加法获取仿真的超声多普勒时域信号。用快速傅里叶变换(FFT)计算仿真超声多普勒信号的频谱,从中计算最大频率、平均频率和频谱宽度等参数,分析它们在不同流速和狭窄程度下的特征,为血管疾病的诊断提供敏感的参数。     

Design and implementation of a smartphone-based portable ultrasound pulsed-wave Doppler device for blood flow measurement

Blood flow measurement using Doppler ultrasound has become a useful tool for diagnosing cardiovascular diseases and as a physiological monitor. Recently, pocket-sized ultrasound scanners have been introduced for portable diagnosis. The present paper reports the implementation of a portable ultrasound pulsed-wave (PW) Doppler flowmeter using a smartphone. A 10-MHz ultrasonic surface transducer was designed for the dynamic monitoring of blood flow velocity. The directional baseband Doppler shift signals were obtained using a portable analog circuit system. After hardware processing, the Doppler signals were fed directly to a smartphone for Doppler spectrogram analysis and display in real time. To the best of our knowledge, this is the first report of the use of this system for medical ultrasound Doppler signal processing. A Couette flow phantom, consisting of two parallel disks with a 2-mm gap, was used to evaluate and calibrate the device. Doppler spectrograms of porcine blood flow were measured using this stand-alone portable device under the pulsatile condition. Subsequently, in vivo portable system verification was performed by measuring the arterial blood flow of a rat and comparing the results with the measurement from a commercial ultrasound duplex scanner. All of the results demonstrated the potential for using a smartphone as a novel embedded system for portable medical ultrasound applications.     

Direct bidirectional angle-insensitive imaging of the flow signal intensity in Doppler optical coherence tomography

We introduce a new method, to our knowledge, for direct detection of flow signal intensity by stationary target rejection. In our system, two delay lines are constructed with identical scanning speed and ranging depth. One delay line is used for depth ranging as well as phase modulation, and the other one acts as a full-range retroreflector (FRRR). The signal from this FRRR carries the overall features of local phase modulation, and it is used as the local oscillator for coherent demodulation. With this setup, stationary targets can be rejected at a 4-kHz high-pass cutoff frequency of the filter that follows the demodulator, compared with 20 kHz for conventional fixed-frequency demodulation. This technique features angle insensitivity and provides flow direction as well by implementing standard in-phase and quadrature detection. Besides the direct directional detection of flow signal intensity, flow speed information can be acquired with postprocessing.     

Emboli detection using the Doppler ultrasound technique

Embolic detection is very important to the early diagnosis of vessel disease. The Doppler ultrasound technique is one of the common methods to detect the emboli non-invasively. When the emboli pass through the sample volume of the Doppler ultrasound instrument, there exist high intensity transient Doppler signals. Thus the emboli can be detected directly from the variation of Doppler signal amplitude. Since there may be some disturbance in the system, this general detection method has great limitation. To improve the accuracy of emboli auto-detection, several novel methods are studied to obtain the sensitive characteristic of the emboli signals using the new signal processing theories.     

EMD和二进正交小波分解对旋转机械振动信号处理效果的研究

二进正交小波分解通过一组高、低通正交镜像滤波器，以二分频形式把信号分解到各个频段中，经验模式分解（EMD）具有类似性质。但由于分解原理问的差异，对同一信号有不同处理效果。以故障滚动轴承振动信号处理为例，对比分析两种方法的处理效果，表明对于旋转机械，由于故障信号往往表现为调幅形式，而且相互间具有不同的载波与调制波频率，EMD方法是以信号的真实物理意义实现自适应二分频分解，能完整保留各个调幅信号，二进正交小波变换严格按照数学意义分解信号，势必破坏调幅信号完整性，影响故障定位，对比处理效果，EMD提取故障特征频率的效果要比二进正交小波分解好。