应用MATLAB获取超声多普勒音频信号频谱的方法研究

超声多普勒血流检测信号的频谱以及最大频率曲线包含着重要的血流生理参数和动力学参数,能反映血流状况以及血管痰病信息.本文提出了应用matlab获取超声多普勒音频信号频谱的方法,从而进一步获得最大频率曲线等信息.     

超声能量多普勒与弹性成像对冈上肌肌腱炎的诊断及与预后的相关分析

目的：探索超声能量多普勒与弹性成像对冈上肌肌腱炎的诊断及与预后的相关性。方法：回顾性分析在2018年5月至2020年10月期间选取的70例健康体检者(对照组)、72例冈上肌肌腱炎患者(观察组),均进行超声检查,分析观察组患者患侧、健侧超声声像图表现,启动超声能量多普勒、弹性成像模式,比较两组受检者剪切模量值、SWV值、血流信号分级、弹性超声分级,用ROC曲线分析各项数值对冈上肌肌腱炎及预后的预测价值,并用Spearman法分析各项参数与预后的相关性。结果：观察组患者患侧的血流增多率、回声杂乱率、内部钙化点率、回声不均率均高于健侧(P＜0.05)。观察组SWV值、剪切模量值、血流信号分级、弹性超声分级高于对照组(P＜0.05),经ROC曲线分析,SWV值、剪切模量值、弹性超声分级、血流信号分级及四项联合早期预测冈上肌肌腱炎的AUC分别为0.932、0.917、0.905、0.921、0.996。同时预后良好组血流信号分级、弹性超声分级、剪切模量值、SWV值低于预后不佳组(P＜0.05),经ROC曲线分析,SWV值、剪切模量值、弹性超声分级、血流信号分级及四项联合早期预测预后情况的AUC分别为0.881、0.922、0.914、0.914、0.995,经Spearman法分析,预后情况与SWV值、剪切模量值、血流信号分级、弹性超声分级呈正相关性。结论：超声能量多普勒联合弹性成像可预测冈上肌肌腱炎发生、发展、预后情况。     

心脏运动对血流速度时间积分测定影响的模拟实验研究

目的 探讨体外模拟心脏运动对多普勒血流流速曲线速度时间积分(VTI)测定的影响。方法用自行设计的TD-3型心底运动模拟仪和血流模拟器，记录两者在不同速度状态下分别运动和同步运动时多普勒流速曲线的特点．观察模拟心脏运动对模拟血流流速曲线VTI测定的影响及其定量关系。结果在模拟心脏运动作用下，模拟血流改变了原有的流速曲线波形，两者同向运动时，模拟血流流速曲线VTI为两者单独运动时的VTI之和．反向运动时为两者单独运动的VTI之差．而模拟心腔运动所产生的多普勒频移信号的速度和频率没有变化。结论模拟心脏运动对模拟血流流速曲线VTI测值有明显影响，在用多普勒方法测量血流量时应当考虑到心脏运动对多普勒测值的影响并加以校正。     

体外模拟实验研究心脏运动对频谱多普勒血流速度测定的影响

目的：通过体外模拟实验，研究心脏运动对频谱多普勒血流速度测定的影响。方法：设计一套仪器，使它模拟心脏运动的速度和频率并使在其内流动的模拟血液的流速和频率及这两种运动的开启和停止时间都分别可控，观察模拟血流的频谱多普勒在模拟心脏运动影响下的变化及它们之间量的关系。结果：在模拟心脏运动作用下，原来的模拟血流波形已不存在，代之以模拟心脏运动和模拟血流控速度矢量相加规律所组成的复合波，而模拟心脏运动所产生的多普勒频移信号的振幅和频率都未改变且与上述血流信号并存于频谱中，结论：通常所谓的血流速度频谱实际上是血细胞在心脏内流动速度和心脏运动速度的矢量和。即两项运动的复合频谱。所以，为减少误差，在用多普勒血流速度频谱测定血流参数时，应考虑校正问题。     

肾脏血流灌注的评估：造影增强彩色多普勒时间-强度曲线分析

背景：超声评价肾脏功能主要通过测量较粗大的肾脏各级动脉的血流参数或肾切面内动脉彩色血流面积所占的比例来推断，误差较大。目的：应用超声仪器随机配置的彩色多普勒时间-强度曲线软件评价肾脏血流灌注情况。设计：动物实验观察。单位：广州市第一人民医院功能检查科。材料：实验于1999-01／2000-04在广州军区广州总医院动物实验室完成，选择8只健康新西兰兔，雌雄各4只，体质量2.5～3．5k。观察肾脏16个。声学造影剂为全氟显，主要成分为声振白蛋白的微泡，微泡内有一定浓度的全氟丙烷气体。方法：兔外周静脉团注造影剂全氟显后用彩色多普勒能量图、彩色多普勒血流显像和彩色多普勒能量谐波成像连续采集肾脏彩色血流图像，随机配置软件显示时间-强度曲线。主要观察指标：造影增强肾脏血流灌注时间一强度曲线的形态。结果：进入结果分析8只家兔。肾脏血流造影增强的时间一强度曲线呈单峰状，上升支陡直，下降支平缓。调节时间轴上的感兴趣线可作定量分析，回放显示注射造影剂后对应某一时刻的造影增强的彩色多普勒图像。结论：造影增强彩色多普勒血流显像和彩色多普勒能量图的时间-强度曲线能有效的观察肾脏血流灌注特征，既可显示整个肾脏的血流灌注情况，也用于观察低血流灌注区域，发现病灶进一步绘制肾功能图。     

造影增强彩色多普勒时间-强度曲线观察肾血流灌注的实验研究

目的：探讨超声随机配置的时间－强度曲线软件对肾血流灌注的评价。方法：兔外周静脉团注造影剂“全氟显”后用彩色多普勒能量图和彩色多普勒血流显像连续采集彩色血流图像,随机配置软件显示时间－强度曲线,调节时间轴上的“感兴趣线”作定量分析。结果：造影增强的时间－强度曲线呈单峰状,上升支陡直,下降支平缓,结论：造影增强彩色多普勒血流显像和彩色多普勒能量图的时间－强度曲线可有效地观察肾血流灌注特征。     

痛量多普勒显像和彩色多普勒血流显像对肝癌并发门脉栓子的对 …

本文应用能量多普勒显像（ＰＤＩ）及彩色多普勒血流显像（ＣＤＦＩ）探查了２９例肝癌并发症脉栓子的患者，结果示：在增益、脉冲重复频率及壁滤波相同的情况下，ＰＤＩ对门脉不同状态的血流信号：血流束细、充孕缺损或线状血流束的显示较ＣＤＦＩ清晰，特别早血流束边界。在降低脉冲重复频率以及增益的情况下，可使部分间断的血流信号连接起来，并能显示ＣＤＦＩ所不能显示的细胞小血流信号。由于ＰＤＩ不能显示血流的方向和速度，     

彩色多普勒超声检测肝癌血流及其与MVD、VEGF表达的关系

目的：利用彩色多普勒超声检测肝癌血流并探讨其与微血管密度（MVD）、血管内皮生长因子（VEGF）的关系。方法：采用彩色多普勒超声检测45例肝癌肿瘤血流信号，计测阻力指数（RI）、相对灌注率，血流分级。采用免疫组织化学技术检测肿瘤MVD及VEGF表达。结果：肿瘤内阻力指数（RI）、相对灌注率、血流等级和MVD相关，相对灌注率、血流等级和VEGF表达相关，阻力指数与VEGF表达不相关。结论：彩色多普勒超声联合上述免疫组织化学指标可从不同角度反映肝癌的血管生成特征，有助于对肝癌血管生成进行评价。     

彩色多普勒超声在阴囊疾病诊断中的应用

目的：探讨彩色多普勒超声对阴囊疾病的诊断价值。方法：回顾分析25例阴囊疾病的临床资料，二维超声及彩色多普勒血流灌注信息。结果：睾丸肿块表现为无痛性肿大，肿块内血流灌注信息对良恶性的鉴别提供依据。结论：彩色多普勒超声对阴囊疾病的诊断准确率较高。     

彩色多普勒在诊断肝血管瘤中的价值

目的： 探讨彩色多普勒在诊断肝血管瘤中的应用价值。方法： 应用彩色多普勒血流图 （ＣＤＦＩ） 及彩色能量多普勒血流图 （ＰＤＩ）, 结合脉冲多普勒频谱对５４ 例 ８９ 个肝血管瘤进行研究。结果： ＣＤＦＩ对肝血管瘤内血流显示敏感性较低, 显示率２２．４７％ ; ＰＤＩ对肝血管瘤内血流显示敏感性很高, 显示率９６．６％ , 两者对病灶内血流显示率有显著差异性 （Ｐ＜ ０．０１）。结论： 我们认为 ＰＤＩ对肝血管瘤的诊断及鉴别诊断有很高的价值, 值得推广应用。     

彩色多普勒血流会聚法评估动脉导管未闭分流程度

用彩色多普勒血流会聚法对２０例动脉导管未闭患者的左向右分流率Ｆ进行测定，并根据Ｆ值计算出动脉导管的横截面积Ａ。结果表明，血流会聚法所测分流率Ｆ与频谱Ｄｏｐｐｌｅｒ法所测的分流量Ｑｐ－Ｑｓ、Ｑｐ／Ｑｓ以及导管两端的压差△Ｐ和左室内径ＤＬＶ之间均具有很好的相关性（ｒ分别为０．８１，０．６２，０．６９和０．５３，Ｐ值分别小于０．００１，０．００５，０．００１和０．０１）。根据Ｆ值计算出的导管横截面积Ａ与两组切面上直接测得的导管内径Ｄｄ也具有极好的相关关系（ｒ＝０．８１，Ｐ值＜０．００１）。Ｑｐ／Ｑｓ≥２１所对应的Ｆ值明显高于Ｑｐ／Ｑｓ＜２１所对应的Ｆ值（Ｐ值＜０．００５）。彩色多普勒血流会聚法能够较为快速、准确地评估动脉导管未闭的左向右分流程度     

Multigated contrast-enhanced power Doppler to measure blood flow in mice tumors

This study evaluated an image-gating method using contrast-enhanced power Doppler ultrasound (US) to estimate blood perfusion in mice tumors. A mathematical model that compensates for the effect of bubble destruction by US pulses was used to determine contrast flow through an image plane. Multigated power Doppler images were obtained following contrast injection. Contrast flow index (CFI) was determined by measuring the area under the color level vs. time curve for each gating frequency. CFI was compared with true flow. The method was first evaluated using a flow phantom with variable flow rates, and then verified in a mouse model with implanted tumors. Color levels in Doppler images were modulated with gating frequency due to variable destruction of microbubbles by US pulses. CFI measured from the images correlated strongly with true flow in the flow phantom (r(2) = 0.87). The proposed method yielded reproducible CFI for mice tumors, suggesting that multigated contrast-enhanced power Doppler imaging may provide noninvasive measurement of tumor perfusion in mice.     

Comparison of conventional and transverse Doppler sonograms

When measuring flow velocity using the conventional ultrasonic Doppler effect, beam axis-to-flow angles approaching 90 degrees are avoided as the Doppler spectrum frequency shift is known to go to zero at this angle. In this paper, the conventional Doppler technique is compared with the transverse Doppler method, in which the Doppler spectrum bandwidth is used to estimate flow, allowing flow to be probed at 90 degrees. The comparison is made using a moving thread flow phantom capable of executing various velocity profiles. This technique may allow the probing of vessels that are inaccessible to conventional oblique probing, thus complementing the conventional Doppler technique.     

彩色多普勒能量图与彩色多普勒血流图检测肿瘤内血流的对照研究

应用彩色多普勒血流图（ＣＤＦＩ）、多普勒能量图（ＣＤＰＩ）结合脉冲多普勒观测４８例（６８个病灶）盆腹腔器官肿块内血流情况。结果显示：ＣＤＰＩ肿块内血流显示率及显示质量优于ＣＤＦＩ；ＣＤＰＩ显示下取样脉冲多普勒频谱质量优良率及血流参数可信度也明显高于ＣＤＦＩ显示下取样。我们认为ＣＤＰＩ是一种更敏感的彩色血流显像技术，具有一定的实用价值，值得推广应用。     

A method to estimate wall shear rate with a clinical ultrasound scanner

A simple technique to estimate the wall shear rate in healthy arteries using a clinical ultrasound scanner has been developed. This method uses the theory of fully developed oscillatory flow together with a spectral Doppler trace and an estimate of mean arterial diameter. A method using color flow imaging was compared with the spectral Doppler method in vascular phantoms and found to have errors that were on average 35% greater. Differences from the theoretic value for the time averaged wall shear rate using the spectral Doppler method varied by artery: brachial −9 (1) %; carotid −7 (1) %; femoral −22 (4) %; and fetal aorta −17 (10) %. Test measurements obtained from one healthy volunteer demonstrated the feasibility of the technique in vivo. E-mail: (james.blake@ed.ac.uk)     

Dependence of power Doppler image on a high pass filter instrumented in ultrasound machine

The aim of this study was to examine the influence of flow velocity, beam incident angle and a wall motion filter on the intensity of power Doppler image of steady flow in vitro. Power Doppler images of flow were recorded using a 7.5-MHz linear transducer with the fixed repetition frequency, gain and frame rate settings at the velocity levels of 15, 20, 35 and 65 cm/s with the beam incident angles of 30° and 60°. The power (P) of received Doppler signal was digitized to 25 gray values (G) for imaging using a wall motion filter with the transfer function: G = a × log P + b (a, b = constant values). Image intensity was measured at the center of the flow image off-line and compared with the flow velocity measured by conventional pulsed wave Doppler. Below the Nyquist limit, G increased as velocity increased, and G with the incident angle 30° was lower than those with 60°. Overall relationship between the Doppler shift frequency and the image intensity exhibited an excellent correlation when fit to the theoretical curve derived from the filter property (r = 0.97). The signal intensity of power Doppler image of flow depends upon the mean Doppler frequency shift or the flow velocity and was clearly affected by the wall motion filter.     

Novel Method for Fetal and Maternal Heart Rate Measurements Using 2-D Ultrasound Color Doppler Flow Images

Fetal heart rate (FHR) and maternal heart rate (MHR) are important indicators of fetal well-being during pregnancy. A common method in clinical examination is to estimate the FHR using the Doppler shift of echoes from umbilical artery blood flow based on an ultrasound pulsed-wave (PW) Doppler technique. Similarly, a sampling gate can be located at the maternal blood flow to measure MHR using PW Doppler. Ultrasound color Doppler flow imaging (CDFI) is one of the most commonly used imaging modes for clinical fetal examinations. Color coding is employed to display the blood flow velocity and direction in color grades according to the Doppler shift. Continuous CDF images contain dynamic changes characteristics of the blood flow. The periodic characteristics can be used to obtain heart rate information. Therefore, here we propose a novel method to measure FHR and MHR simultaneously using CDF images. The proposed method calculates the histogram of color similarity of CDF images to initially extract the periodic characteristics of the CDF image sequence. The histogram of color similarity function is then processed by a bandpass filter and autocorrelation operation to reduce noise and enhance periodicity. Finally, peak detection is performed on the processed signal to obtain the period and estimate the heart rate. The proposed method can measure the FHR and MHR in parallel after selecting two regions containing the umbilical artery and maternal blood flow, respectively. Thus, the method has high computational efficiency. The proposed method was evaluated on a Doppler flow phantom and clinical CDF images and then compared with the PW Doppler method. The correlation analysis and Bland–Altman plots reveal that the proposed method agrees well with the PW Doppler. It is a sanity check method for real-time clinical FHR and MHR measurements.     

Doppler angle estimation of pulsatile flows using AR modeling

In quantitative ultrasonic flow measurements, the beam-to-flow angle (i.e., Doppler angle) is an important parameter. An autoregressive (AR) spectral analysis technique in combination with the Doppler spectrum broadening effect was previously proposed to estimate the Doppler angle. Since only a limited number of flow samples are used, real-time two-dimensional Doppler angle estimation is possible. The method was validated for laminar flows with constant velocities. In clinical applications, the flow pulsation needs to be considered. For pulsatile flows, the flow velocity is time-varying and the accuracy of Doppler angle estimation may be affected. In this paper, the AR method using only a limited number of flow samples was applied to Doppler angle estimation of pulsatile flows. The flow samples were properly selected to derive the AR coefficients and then more samples were extrapolated based on the AR model. The proposed method was verified by both simulations and in vitro experiments. A wide range of Doppler angles (from 3o degrees to 78 degrees) and different flow rates were considered. The experimental data for the Doppler angle showed that the AR method using eight flow samples had an average estimation error of 3.50 degrees compared to an average error of 7.08 degrees for the Fast Fourier Transform (FFT) method using 64 flow samples. Results indicated that the AR method not only provided accurate Doppler angle estimates, but also outperformed the conventional FFT method in pulsatile flows. This is because the short data acquisition time is less affected by the temporal velocity changes. It is concluded that real-time two-dimensional estimation of the Doppler angle is possible using the AR method in the presence of pulsatile flows. In addition, Doppler angle estimation with turbulent flows is also discussed. Results show that both the AR and FFT methods are not adequate due to the spectral broadening effects from the turbulence.     

Improved transverse flow estimation using differential maximum Doppler frequency

Conventional Doppler technique can only provide the axial component of the blood flow vector, which is actually a three dimensional (3-D) quantity. To acquire the complete flow vector, estimations of the other two velocity components are essential. For the two dimensional (2-D) Doppler-bandwidth-based transverse estimation, however, accuracy is generally limited because of the complex dependence of the Doppler spectral shape on the flow variation within the sample volume. Two factors that may lead to the Doppler spectral change were considered in this study. One is the position offset of the sample volume and the other is the length of the sample volume. Simulations were performed and experimental data were also collected. Results indicate that the position offset may result in severe underestimation of Doppler shift frequency. Consequently, Doppler bandwidth is overestimated when it is determined by the difference between Doppler shift frequency and maximum Doppler frequency. Compared with the position offset, influence of the length of sample volume on the Doppler bandwidth is minor. To overcome this problem, a novel method, which is based on the differential maximum Doppler frequency, is proposed. Specifically, two beams with different beam widths are simultaneously generated to observe the blood flow and the difference between the corresponding maximum Doppler frequencies is used to estimate the transverse velocity. It is demonstrated that the accuracy and stability of transverse estimation are significantly improved by the proposed method even when the position offset is present.     

Implementation of spectral width Doppler in pulsatile flow measurements

In this paper, we present an automatic beam-vector (Doppler) angle and flow velocity measurement method and implement it in pulsatile flow measurements using a clinical Doppler ultrasound system. In current clinical Doppler ultrasound flow velocity measurements, the axis of the blood vessel needs to be set manually on the B-scan image to enable the estimation of the beam-vector angle and the beam-vector angle corrected flow velocity (the actual flow velocity). In this study, an annular array transducer was used to generate a conical-shaped and symmetrically focused ultrasound beam to measure the flow velocity vectors parallel and perpendicular to the ultrasound beam axis. The beam-vector angle and flow velocity is calculated from the mode frequency (f(d)) and the maximum Doppler frequency (f(max)) of the Doppler spectrum. We develop a spectrum normalization algorithm to enable the Doppler spectrum averaging using the spectra obtained within a single cardiac cycle. The Doppler spectrum averaging process reduces the noise level in the Doppler spectrum and also enables the calculation of the beam-vector angle and flow velocity for pulsatile flows to be measured. We have verified the measurement method in vivo over a wide range of angles, from 52 degrees to 80 degrees, and the standard deviations of the measured beam-vector angles and flow velocities in the carotid artery are lower than 2.2 degrees and 12 cm/s (about 13.3%), respectively.