Embolic Doppler ultrasound signal detection using discrete wavelet transform

Asymptomatic circulating emboli can be detected by Doppler ultrasound. Embolic Doppler ultrasound signals are short duration transient like signals. The wavelet transform is an ideal method for analysis and detection of such signals by optimizing time-frequency resolution. We propose a detection system based on the discrete wavelet transform (DWT) and study some parameters, which might be useful for describing embolic signals (ES). We used a fast DWT algorithm based on the Daubechies eighth-order wavelet filters with eight scales. In order to evaluate feasibility of the DWT of ES, two independent data sets, each comprising of short segments containing an ES (N=100), artifact (N=100) or Doppler speckle (DS) (N=100), were used. After applying the DWT to the data, several parameters were evaluated. The threshold values used for both data sets were optimized using the first data set. While the DWT coefficients resulting from artifacts dominantly appear at the higher scales (five, six, seven, and eight), the DWT coefficients at the lower scales (one, two, three, and four) are mainly dominated by ES and DS. The DWT is able to filter out most of the artifacts inherently during the transform process. For the first data set, 98 out of 100 ES were detected as ES. For the second data set, 95 out of 100 ES were detected as ES when the same threshold values were used. The algorithm was also tested with a third data set comprising 202 normal ES; 198 signals were detected as ES.     

DNA computing from a signal processing viewpoint

In this article, an analysis of Adleman's experiment and a review of DNA computing applications from a signal-processing point of view are provided. In addition, certain key parts of DNA computing are emphasized, such as the code word design, to which the application of signal processing theory and techniques can offer significant advantages. The goal of this article is to introduce to the signal processing community a new unexplored area of research.     

Pulsed Doppler signal processing for use in mice: applications

We have developed a high-frequency, high-resolution Doppler spectrum analyzer (DSPW) and compared its performance against an adapted clinical Medasonics spectrum analyzer (MSA) and a zero-crossing interval histogram (ZCIH) used previously by us to evaluate cardiovascular physiology in mice. The aortic velocity (means /spl plusmn/ SE: 92.7 /spl plusmn/ 2.5 versus 82.2 /spl plusmn/ 1.8 cm/s) and aortic acceleration (8194 /spl plusmn/ 319 versus 5178 /spl plusmn/ 191 cm/s/sup 2/) determined by the DSPW were significantly higher compared to those by the MSA. Aortic ejection time was shorter (48.3/spl plusmn/ 0.9 versus 64.6 /spl plusmn/ 1.8 ms) and the isovolumic relaxation was longer (17.6 /spl plusmn/ 0.6 versus 13.5 /spl plusmn/0.6 ms) when determined by the DSPW because it generates shorter temporal widths in the velocity spectra when compared to the MSA. These data indicate that the performance of the DSPW in evaluating cardiovascular physiology was better than that of the MSA. There were no significant differences between the aortic pulse wave velocity determined by using the ZCIH (391 /spl plusmn/ 16 cm/s) and the DSPW (394 /spl plusmn/ 20 cm/s). Besides monitoring cardiac function, we have used the DSPW for studying peripheral vascular physiology in normal, transgenic, and surgical models of mice. Several applications such as the detection of high stenotic jet velocities (>4 m/s), vortex shedding frequencies (250 Hz), and subtle changes in wave shapes in peripheral vessels which could not obtained with clinical Doppler systems are now made possible with the DSPW.     

ATTITUDE RATE ESTIMATION BY GPS DOPPLER SIGNAL PROCESSING

A method is presented for near-Earth spacecraft or aviation vehicle‘s attiude rate cstimation by using relative Doppler frequency shift of the Global Positioning System(GPS)carrier.It comprises two GPS receiving antennas,a signal processing circuit and an algorithm.The whole system is relatvely simple,the cost and weight,as well power consumption,are very low.     

Breast thermography from an image processing viewpoint: A survey

Breast cancer is the leading cause of death among women. This fact justifies researches to reach early diagnosis, improving patients’ life expectancy. Moreover, there are other pathologies, such as cysts and benign neoplasms that deserve investigation. In the last ten years, the infrared thermography has shown to be a promising technique to early diagnosis of breast pathologies. Works on this subject presented results that justify the thermography as a complementary exam to detect breast diseases. Several papers on the use of infrared imaging for breast screening can be found in the current medical literature. This survey explores and analyses these works in the light of their applications in computer vision. Consequently, the comments are organized according to the main steps of pattern recognition systems. These include: image acquisition protocols, exams storage, segmentation methods, feature extraction, classification or diagnostic and computer modelling. Main contributions of discussed papers are summarized in tables to provide a structured vision of the aspects involved in breast thermography.     

基于小波去噪的激光多普勒振动信号处理

为了降低激光多普勒振动信号中噪声产生的影响,采用基于改进小波去噪算法的激光多普勒振动信号处理方法,将尺度引入阈值函数,确立新的评价指标用于选择最优分解层数,从而来改进小波阈值去噪算法,并利用改进的算法处理振动信号, 进行了仿真分析和实验验证,取得了处理前后的振动数据。结果表明, 改进算法处理仿真信号的信噪比比原有算法提升19.4%;实验测得音叉振动频率为515Hz,与实际音叉频率基本吻合。这一结果对降低激光多普勒振动信号中噪声的影响、获取振动状态是有帮助的。     

零差激光测振系统中含噪多普勒信号处理方法

针对零差激光测振系统中多普勒信号的噪声导致信号正交校正困难、增大测量误差的问题,提出了含噪多普勒信号处理方法。首先利用平滑滤波对两路含噪多普勒信号进行降噪处理,再通过最小二乘法对非正交多普勒信号进行校正,然后采用单位圆校正算法二次校正成正交信号,最后利用微分相除积分操作解调出振动信号。实验结果表明,本文方法能有效解调振...     

激光多普勒信号的几种处理方法在Matlab中的实现

激光多普勒信号具有强度弱、信噪比低、噪声干扰大等特点。简要介绍快速傅里叶变换（FFT）、数字相关、Welch修正周期图功率谱估计算法的基本原理,并在Matlab中对仿真信号和实测的激光多普勒信号用以上几种方法进行数据处理并做比较。实验结果表明,它们都能有效地从噪声中提取信号,数字相关技术能更好地去除噪声,但都存在精度不够高的问题,需要对信号处理方法做进一步的研究。     

Pulsed Doppler signal processing for use in mice: design and evaluation

We have developed and evaluated a high-frequency, real-time pulsed Doppler and physiological signal acquisition and analysis system specifically for use in mice. The system was designed to provide sampling rates up to 125 kilosamples/s (ksps) with software controlled data acquisition and analysis in real-time. Complex fast Fourier transforms are performed every 0.1 ms (or longer up to 10 ms) to provide 0.1-ms time resolution and using 64-1024 sample segments of the Doppler audio signals resulting in frequency resolution ranging from 122-1953 Hz. The system was evaluated by its response to frequency swept signals with slopes (accelerations) and magnitudes (velocities) comparable to actual blood velocity signals in mice. Signals up to a maximum frequency of 125 kHz and a maximum acceleration of 20 MHz/s were processed and displayed. This corresponds to a maximum velocity of 480 (960) cm/s and a maximum acceleration of 750 (1500) m/s2 when Doppler shifts are measured with a 20- (10-) MHz probe, thereby allowing us to measure high stenotic jet velocities. The directional transitions of the spectrogram across zero frequency and across Nyquist frequency (sampling rate/2) were smooth with no discernible artifacts. Signals with period as low as 2 ms were processed and displayed at sweep speed that is ten times that in clinical Doppler systems, so that measurements of small temporal events can be made with precision. Thus, the new system can measure higher blood velocities with higher spatial and temporal resolution than is possible using clinical Doppler systems adapted for use in mice.     

Selection of signal detection threshold in Doppler spectrum analyzer

It is shown, that for spectrum analyzer noise immunity increase, during processing of optical Doppler location signal with unknown frequency, random appearance time and low signal to noise ratio it is advisable to use methods of false alarm probability decrease, where decision about useful signal presence is made according to two pulses appearance at the matched filter output. These pulses have the same delay times with regard to signal analysis beginning time. This methodology application for signal detection allows to decrease a false alarm probability with regard to one period of analysis in case of the same values of threshold.     

A signal processing approach to symmetry detection.

We present an algorithm that detects rotational and reflectional symmetries of two-dimensional objects. Both symmetry types are effectively detected and analyzed using the angular correlation (AC), which measures the correlation between images in the angular direction. The AC is accurately computed using the pseudopolar Fourier transform, which rapidly computes the Fourier transform of an image on a near-polar grid. We prove that the AC of symmetric images is a periodic signal whose frequency is related to the order of the symmetry. This frequency is recovered via spectrum estimation, which is a proven technique in signal processing with a variety of efficient solutions. We also provide a novel approach for finding the center of symmetry and demonstrate the applicability of our scheme to the analysis of real images.     

Collaborative signal and information processing: an information-directed approach

This paper describes information-based approaches to processing and organizing spatially distributed, multimodal sensor data in a sensor network. Energy-constrained networked sensing systems must rely on collaborative signal and information processing (CSIP) to dynamically allocate resources, maintain multiple sensing foci, and attend to new stimuli of interest, all based on task requirements and resource constraints. Target tracking is an essential capability for sensor networks and is used as a canonical problem for studying information organization problems in CSIP. After formulating a CSIP tracking problem in a distributed constrained optimization framework, the paper describes information-driven sensor query and other techniques for tracking individual targets as well as combinatorial tracking problems such as counting targets. Results from simulations and experimental implementations have demonstrated that these information-based approaches are scalable and make efficient use of scarce sensing and communication resources.     

用于光学相位检测的数字信号处理系统

介绍了一种利用数字信号处理技术和虚拟仪器技术实现对微弱光学相位信号进行高精度频率、幅度测量的方法。该方法实现了反馈式数据采样率的设定、自适应数字带通带阻滤波器和全数字相敏检波等功能,并且可以对信号相位和强度以及谐波进行精确测量     

基于FPGA的多普勒测振计信号采集与处理系统设计

为了实现激光水声浅海地形遥感探测中水声信号的实时解调与处理,设计了一种基于FPGA的激光多普勒测振计信号采集与处理系统。以CycloneⅡ系列FPGA为核心控制模块,结合ADS1174模数转换芯片、DAC8551数模转换芯片和MAX3232收发芯片,实现了高速数据采集和串口通信。该信号采集系统具有性能可靠、实时性强、集成度高、扩展灵活等特点,并且通过试验验证了其功能的正确性。     

基于混合卷积窗六谱线插值的多普勒信号处理

激光多普勒测速系统信号处理的过程中,通常采用快速傅里叶变换提取多普勒频移进而计算出被测物体运动速度,由于频谱泄露和栏栅效应的影响,会导致测量精度降低。本文提出了一种四项Nuttall窗和五项Rife Vincent窗的混合卷积窗函数结合改进的六谱线插值算法来降低频谱泄露和栏栅效应所带来的影响,从而提高激光多普勒信号处理精度。搭建了双光束后向散射差动式激光多普勒测速平台,通过仿真和实测得出在加入了RSN=-10dB的高斯白噪声的情况下使用该混合卷积窗所测量的最小相对误差为00027,而分别使用两个单一的窗函数测量的最小相对误差分别为00103和00461。从而验证了本方法的有效性。     

Power-line interference detection and suppression in ECG signal processing

A novel power-line interference (PLI) detection and suppression algorithm is presented to preprocess the electrocardiogram (ECG) signals. A distinct feature of this proposed algorithm is its ability to detect the presence of PLI in the ECG signal before applying the PLI suppression algorithm. No PLI suppression operation will be performed if PLI is not detected. We propose a PLI detector that employs an optimal linear discriminant analysis (LDA) algorithm to make a decision for the PLI presence. An efficient recursive least-squares (RLS) adaptive notch filter is also developed to serve the purpose of PLI suppression. Experimental results demonstrate superior performance of this proposed algorithm.     

语音信号中字词端点检测方法的两项改进

为了提高传统字词端点检测方法检测端点的准确性,分析了传统检测方法的不足,针对语音信号直流分量不为零和长音节尾音被误切割等特殊情况,提出了字词端点检测改进措施。经实验,改进措施有较好实用效果。     

A mean blood velocity statistic for the Doppler signal from anarrow ultrasound beam

An easily calculable statistic proportional to the instantaneous spatial mean blood velocity through a vessel cross section is derived from Doppler power spectral estimates for the case where the Doppler beam is assumed to be of negligible thickness compared to the vessel diameter. This is an alternative statistic to that derived where uniform insonation is assumed, an assumption thought to be poorer in many real cases. The main requirement is that the velocity profile is monotonic increasing from the vessel wall to the vessel center. Errors in each statistic are compared for a variety of true beam dimensions, using a variety of velocity profiles, and the new statistic is shown to incur less error for Gaussian beam response profiles with a standard deviation less than 0.4 of the vessel radius, or for rectangular response profiles with a width less than 0.65 of the vessel diameter. If an estimate can be made of the true beam dimensions and vessel diameter, a weighted sum of the two statistics can give a more accurate estimate of mean velocity. The case of a beam displaced from the center of the vessel is also considered, and errors are found to be less than 4% for a displacement of 20% of the vessel radius     

爆炸物检测中微弱NQR信号的处理

介绍了用核四极矩共振技术检测爆炸物品的原理及检测过程中信号的处理方法。根据NQR测量中接收信号极其微弱的特点,针对以数字累加技术处理NQR信号的常规方法,提出了利用相关检测的方法来处理核四极矩共振（NQR）信号,该方法可以更有效地提高信噪比,并消除随机噪声和外界干扰对接收信号的干扰,从而提高了检测微弱NQR信号的准确性。     

Noninvasive acoustical detection of coronary artery disease: acomparative study of signal processing methods

Previous studies have indicated that, during diastole, the sounds associated with turbulent blood flow through partially occluded coronary arteries should be detectable. To detect such sounds, recordings of diastolic heart sound segments were analyzed using four signal processing techniques: the fast Fourier transform (FFT) autoregressive (AR), autoregressive moving-average (ARMA), and minimum-norm (eigenvector) methods. To further enhance the diastolic heart sounds and reduce background noise, an adaptive filter was used as a preprocessor. The power ratios of the FFT method and the poles of the AR, ARMA, and eigenvector methods were used to diagnose patients as having diseased or normal arteries using a blind protocol without prior knowledge of the actual disease states of the patients to guard against human bias. Of 80 cases, results showed that normal and abnormal records were correctly distinguished in 56 using the fast Fourier transform (FFT), in 63 using the AR, in 62 using the ARMA method, and in 67 using the eigenvector method. These results confirm that high-frequency acoustic energy between 300 and 800 Hz is associated with coronary stenosis