经颅多普勒与彩色多普勒超声联合应用对锁骨下动脉盗血综合征的血流动力学观察

目的 探讨经颅多普勒超声（TCD）与彩色多普勒血流显像联合检查锁骨下动脉盗血综合征的诊断价值。方法 锁骨下动脉盗血综合征患者24例，均经临床检查及相关影像学检查确诊，其中14例经血管造影（DSA）检查，10例经磁共振血管造影检查（MRA），采用TCD方法观察椎动脉颅内段血流方向及频谱的变化，二维超声显示椎动脉颅外段、颈动脉、锁骨下动脉及无名动脉的内膜和内径，彩色及频谱多普勒检测血流方向及速度。结果 TCD检查时，24例患者中18例均表现为椎动脉血流反向，肢体束臂试验反向血流增加，6例血流方向正常，束臂试验患侧椎动脉反向峰值血流速度增快，或由正向变为反向。二维超声示引起锁骨下动脉盗血综合征的病因动脉硬化占90％，大动脉炎占10％。结论 TCD诊断锁骨下动脉盗血综合征具有直观、快捷、准确的优点，结合二维及彩色多普勒超声可以明确锁骨下动脉盗血综合征的病因、病变部位及程度。     

椎－基底动脉供血不足的颅内外超声诊断

鉴于椎－基底动脉供血不足这一多发常见病缺乏客观诊断标准，我们在５６例正常对照组和６２例病变组中用经颅多普勒超声和彩色多普勒超声进行了颅内外脑血管血流检查。其阳性率在病变组分别是９０％和８８％，确立了超声诊断的量化标准，通过与脑干听觉诱发电位、横突孔ＣＴ和磁共振血管造影相比较，证明颅内外超声联合检查是诊断该病的理想方法。     

经颅多普勒超声与磁共振血管成像评估颅内大动脉血管腔及血流动力学变化的比较

背景：血管造影虽为诊断脑血管病的“金标准”，因其有创性不能广泛应用，经颅多普勒超声和头部磁共振血管成像均为无创检查，可用于颅内大动脉血管腔及血流动力学的评估。目的：探讨经颅多普勒超声评估缺血性脑血管病时血流动力学变化的可靠性及与磁共振血管成像的相关性。设计：以患者为观察对象，病例分析。单位：哈尔滨医科大学第一临床医学院神经内科。对象：以2001—04／2002—02哈尔滨医科大学第一临床医学院神经内科收治的脑卒中患者45例为观察对象，所有患者经CT证实为缺血性脑血管病，且对实验知情同意。方法：应用TC-2021经颅多普勒超声仪及VISART1．5T超导MR装置，对45例患者行经颅多普勒超声与磁共振血管成像检查，两次检查相隔时间为1～15d。观察所检大脑中动脉、颈内动脉末端、大脑前动脉、大脑后动脉、椎动脉、基底动脉血管的血流动力学及管腔形态的变化。主要观察指标：①经颅多普勒超声和磁共振血管成像检查患者颅内血管腔和血流动力学结果的相关性。②以磁共振血管成像为标准，比较经颅多普勒超声检查的特异性，敏感性，假阳性，假阴性及符合率。结果：45例患者全部进入结果分析。①经颅多普勒超声和磁共振血管成像检测结果相关性：理论值：Tmin=9．91；X^2=107．92，P〈0．005，可认为两者检出率结果有关；经颅多普勒超声检出率为19．06％，磁共振血管成像检出率为15．25％，两者检出阳性率有差别（X^2=-3．93，P〈0．05）。②以磁共振血管成像为标准，比较经颅多普勒超声发现相应血管病变数，得出诊断异常血管的特异性为94．22％、敏感性为78．10％、假阳性为7．46％，假阴性为23.31％及符合率为89.36％。结论：经颅多普勒超声诊断缺血性脑血管病脑血管异与磁共振血管成像相符性较高，它能准确判定所探及血管功能状态，能较早而敏感反映脑血流动力学的变化。而磁共振血管成像则可直接显示血管形态的改变，两者结合可提高诊断的敏感性和特异性。     

滑车上动脉对脑动脉硬化的彩色多普勒超声检测

目的：通过在面部对颅内血管终末支滑车上动脉（STCA）出颅部的彩色多普勒超声（CDFI）检测，寻找一种对脑动脉硬化（CAS）等颅内血管病变无创性检测的新方法。方法：在29例正常和19例CAS患者面部眶上缘内侧STCA出颅处的眶上孔部位，行CDFI及脉冲多普勒超声检测。结果：对照组STCA出颅部彩色血流信号及多普勒频谱检出率为100％，其位置固定，易于探测，频谱特征与眼动脉相似，为正向三峰型：SP1、SP2、DP峰，SP1＞SP2。CAS患者SP2升高，接近或超过SP1，DP高于对照组（P＜0.05-0.01)，PI、RI低于对照组（P＜0.001)。结论：STCA的CDFI检测是一种准确、方便、价廉、无损伤性、易于掌握、便于推广的诊断CAS等脑血管病变的新方法。     

超声诊断颈动脉异常与颅内血流动力学的研究

目的：为了证实颈总动脉异常与颅内血管的关系，寻找有效的诊断颅内血管疾病的诊断方法，使颅内血管疾病的早期诊断成为可能。方法：用灰阶超声（高频探头）观察颅颈各个大血管的直径和内膜的厚度以及有无粥样斑块，用经颅多普勒超声观察颅底不同血管血流速度和频谱形态。结果：脑血管弹性减退的例数与粥样斑块发生例数高度相关；粥样斑块发生例数和血流速度变慢血管条数发生率高度相关。结论：以上结果显示了两种检查方法对颅外和颅内血管诊断结论上的相关性。     

颈动脉硬化对颅内动脉血流动力学的影响

目的分析颈动脉粥样硬化对颅内动脉血流动力学的影响,为早期发现颅内动脉血流动力学变化并干预其发生以及判断预后提供依据。方法对142例颈动脉粥样硬化的患者进行颅内动脉血流动力学分析。结果颈内动脉严重狭窄或闭塞导致颅外段向颅内动脉灌注减低,远段MCA血流速度减慢,PI值降低,频谱形态改变,呈低搏动性特征改变。在可经颞窗探测的111例颈动脉粥样硬化患者中,引起颅内动脉血流动力学变化的92例,敏感度82.8%,特异度76.3%。结论经颅彩色多普勒超声（TCD）与二维彩色多普勒超声结合对缺血性脑血管病的诊断能够很好地提供颅内外动脉血管病变的相关资料,提高了无创性超声检测在临床的使用价值,是一种可靠的综合性检测方法。     

经颅实时彩色多普勒超声在颅内动脉瘤诊断中的应用

目的探讨经颅实时彩色多普勒成像(TCCS)在颅内动脉瘤诊断中的应用价值。方法采用Sequoia512彩色多普勒超声仪,电子相控阵变频探头,二维实时超声成像的超声探头频率为2.0～5.0MHz,彩色多普勒超声探头频率为2.0MHz,对9例可疑动脉瘤患者在颞窗位置行横断面、纵断面、斜断面及病灶对侧(健侧)相应位置扫查,检测颅内动脉瘤的位置、形态、大小及血流频谱、方向、速度等,并与X线数字减影血管造影(DSA)检查结果进行对比分析。结果TCCS实际成功检测8例,均为颅内段颈内动脉瘤,并经DSA证实;1例因声窗条件欠佳,未能检出血流信号。典型超声表现为在脑动脉血流的条形彩色信号中检出局部膨大呈圆形或椭圆形的血流信号,并呈漩涡状流动,流动速度及方向可有不同。二维超声检测动脉瘤直径为1.2～3.0cm,其中2例为1.2～2.0cm,6例为2.0～3.0cm。结论TCCS可作为行DSA检查前一种筛选颅内动脉瘤的辅助手段及随诊方法。     

颈动脉连续波多普勒超声评估颅内侧支循环

目的探讨颈动脉连续波多普勒超声评估颅内侧支循环。方法对80例无脑供血动脉狭窄性病变患者，在行颈总动脉压迫试验时采用4MHz连续波探头检测对侧颈内动脉起始段和同侧椎动脉寰枢段血流速度变化。并对连续波多普勒超声与经颅多普勒超声检测的侧支循环方式结果进行比较。结果颈动脉连续波多普勒超声检出前交通动脉侧支开放76例（95％），经颅多普勒超声检出前交通动脉侧支开放76例（95％）。在受检的160个后交通动脉侧支中，颈动脉连续波多普勒超声检出后交通动脉侧支开放140个（88％），经颅多普勒超声检出132个（83％）。结论颅外动脉连续波多普勒超声结合颈总动脉压迫试验检测颅内侧支循环既安全又方便，其准确率与经颅多普勒超声一致。     

过度换气对高血压患者脑动脉弹性的估价

经颅多普勒超声（TCD）是近年来出现的一种无创、定量和准确检测颅内血管病变的新技术，它可准确判断颅内Willis环大、中型动脉的各项血流动力学参数。高血压患者在脑部最重要的病理变化是脑细、小动脉痉挛和硬化。本研究旨在用TCD诊断仪观察过度换气前后高血压患者颅内大脑中动脉血流速度的变化，并通过这一动态过程间接地反映脑血管的弹性。     

经颅多普勒超声与磁共振血管成像评估颅内大动脉血管腔及血流动力学变化的比较

背景血管造影虽为诊断脑血管病的"金标准",因其有创性不能广泛应用,经颅多普勒超声和头部磁共振血管成像均为无创检查,可用于颅内大动脉血管腔及血流动力学的评估.目的探讨经颅多普勒超声评估缺血性脑血管病时血流动力学变化的可靠性及与磁共振血管成像的相关性.设计以患者为观察对象,病例分析.单位哈尔滨医科大学第一临床医学院神经内科.对象以2001-04/2002-02哈尔滨医科大学第一临床医学院神经内科收治的脑卒中患者45例为观察对象,所有患者经CT证实为缺血性脑血管病,且对实验知情同意.方法应用TC-2021经颅多普勒超声仪及VISART1.5T超导MR装置,对45例患者行经颅多普勒超声与磁共振血管成像检查,两次检查相隔时间为1～15 d.观察所检大脑中动脉、颈内动脉末端、大脑前动脉、大脑后动脉、椎动脉、基底动脉血管的血流动力学及管腔形态的变化.主要观察指标①经颅多普勒超声和磁共振血管成像检查患者颅内血管腔和血流动力学结果的相关性.②以磁共振血管成像为标准,比较经颅多普勒超声检查的特异性,敏感性,假阳性,假阴性及符合率.结果45例患者全部进入结果分析.①经颅多普勒超声和磁共振血管成像检测结果相关性理论值Tmin=9.91;χ2=107.92,P＜0.005,可认为两者检出率结果有关;经颅多普勒超声检出率为19.06%,磁共振血管成像检出率为15.25%,两者检出阳性率有差别(χ2=3.93,P＜0.05).②以磁共振血管成像为标准,比较经颅多普勒超声发现相应血管病变数,得出诊断异常血管的特异性为94.22%、敏感性为78.10%、假阳性为7.46%,假阴性为23.31%及符合率为89.36%.结论经颅多普勒超声诊断缺血性脑血管病脑血管异与磁共振血管成像相符性较高,它能准确判定所探及血管功能状态,能较早而敏感反映脑血流动力学的变化.而磁共振血管成像则可直接显示血管形态的改变,两者结合可提高诊断的敏感性和特异性.     

Development of a Flexible Implantable Sensor for Postoperative Monitoring of Blood Flow

We have developed a blood flow measurement system using Doppler ultrasound flow sensors fabricated of thin and flexible piezoelectric‐polymer films. These flow sensors can be wrapped around a blood vessel and accurately measure flow. The innovation that makes this flow sensor possible is the diffraction‐grating transducer. A conventional transducer produces a sound beam perpendicular to its face; therefore, when placed on the wall of a blood vessel, the Doppler shift in the backscattered ultrasound from blood theoretically would be 0. The diffraction‐grating transducer produces a beam at a known angle to its face; therefore, backscattered ultrasound from the vessel will contain a Doppler signal. Flow sensors were fabricated by spin coating a poly(vinylidene fluoride–trifluoroethylene) copolymer film onto a flexible substrate with patterned gold electrodes. Custom‐designed battery‐operated continuous wave Doppler electronics along with a laptop computer completed the system. A prototype flow sensor was evaluated experimentally by measuring blood flow in a flow phantom and the infrarenal aorta of an adult New Zealand White rabbit. The flow phantom experiment demonstrated that the error in average velocity and volume blood flow was less than 6% for 30 measurements taken over a 2.5‐hour period. The peak blood velocity through the rabbit infrarenal aorta measured by the flow sensor was 118 cm/s, within 1.7% of the measurement obtained using a duplex ultrasound system. The flow sensor and electronics operated continuously during the course of the 5‐hour experiment after the incision on the animal was closed.     

Measurement of the Doppler Power of Flowing Blood Using Ultrasound Doppler Devices

Measurement of the Doppler power of signals backscattered from flowing blood (henceforth referred to as the Doppler power of flowing blood) and the echogenicity of flowing blood have been used widely to assess the degree of red blood cell (RBC) aggregation for more than 20 y. Many studies have used Doppler flowmeters based on an analogue circuit design to obtain the Doppler shifts in the signals backscattered from flowing blood; however, some recent studies have mentioned that the analogue Doppler flowmeter exhibits a frequency-response problem whereby the backscattered energy is lost at higher Doppler shift frequencies. Therefore, the measured Doppler power of flowing blood and evaluations of RBC aggregation obtained using an analogue Doppler device may be inaccurate. To overcome this problem, the present study implemented a field-programmable gate array-based digital pulsed-wave Doppler flowmeter to measure the Doppler power of flowing blood, in the aim of providing more accurate assessments of RBC aggregation. A clinical duplex ultrasound imaging system that can acquire pulsed-wave Doppler spectrograms is now available, but its usefulness for estimating the ultrasound scattering properties of blood is still in doubt. Therefore, the echogenicity and Doppler power of flowing blood under the same flow conditions were measured using a laboratory pulser–receiver system and a clinical ultrasound system, respectively, for comparisons. The experiments were carried out using porcine blood under steady laminar flow with both RBC suspensions and whole blood. The experimental results indicated that a clinical ultrasound system used to measure the Doppler spectrograms is not suitable for quantifying Doppler power. However, the Doppler power measured using a digital Doppler flowmeter can reveal the relationship between backscattering signals and the properties of blood cells because the effects of frequency response are eliminated. The measurements of the Doppler power and echogenicity of flowing blood were compared with those obtained in several previous studies.     

Doppler ultrasound tracking instrument for monitoring blood flow velocity

Doppler ultrasound (US) is potentially a valuable method for monitoring changes of blood flow velocity over a period of many minutes or even hours, but is seldom used in this way. One difficulty that may have contributed to this is the problem of maintaining a fixed geometry between the US beam and the blood vessel. A method of improving the success of monitoring might be to actively steer the US beam so as to maintain an adequate signal even when small displacements of the transducer occur. We have designed and built a prototype system for this purpose. The system comprises a continuous-wave phased-array transducer controlled by a purpose-built Doppler unit. The system constantly evaluates the quality of the returning Doppler signal in terms of total power and signal-to-noise ratio (SNR) (evaluated by assessing the quality of derived envelope signals), and steers the ultrasonic beam in a manner so as to improve the signal, should this be necessary. The system was tested in vitro, where the automatic tracking of the Doppler signal doubled the effective beam width of the transducer. Further developments that increase sensitivity and steering range should result in US Doppler systems that are better suited to long-term monitoring.     

Intraluminal ultrasound intensity distribution and backscattered Doppler power

Ultrasound (US) incident obliquely on a cylindrical vessel is redistributed in space when the propagation path includes walls with acoustic impedance different from that of the surrounding media. We investigated this using low-density polyethylene (PE) as the vessel wall material. Both simulations and experiments were carried out. Direct hydrophone measurements of the acoustic field were made within a half section of the PE tube, and the distribution of backscattered Doppler power along a scan line was obtained using a range-Doppler instrument. Both simulation and hydrophone results demonstrate lateral shadow regions within the lumen. In every one of various Doppler flow experiments conducted, the backscattered Doppler power, compensated for on-axis transducer behaviour, increased with depth. Simulation results for an incident continuous-wave (CW) plane wave show that it tends to be focused by the curvature of the PE tube walls. The wall interactions are, however, angle-dependent and so the behaviour of a focused US beam depends on the beam as well as the walls. This study demonstrates alterations in the spatial distribution of US within a cylindrical vessel as a result of known vessel wall properties. It also provides evidence that local intensity variations within the lumen affect the relative Doppler power backscattered from small sample volumes.     

Differences in the erythrocyte aggregation level between veins and arteries of normolipidemic and hyperlipidemic individuals

The objectives of this study were to detect differences in the Doppler power backscattered by blood in vivo, and to identify factors affecting the backscattered power. The main hypothesis was that variations in the erythrocyte aggregation level between veins and arteries of normolipidemic and hyperlipidemic individuals can be detected with power Doppler ultrasound. Doppler measurements were performed at 5 MHz, with an Acuson 128 XP/10 system, over the carotid artery and jugular vein, external iliac artery and vein, common femoral artery and vein and popliteal artery and vein. Doppler signals were recorded at the center of each vessel to optimize the detection of erythrocyte aggregation, and processed off-line to obtain the backscattered power. The power of each recording was compensated for Doppler gain differences, tissue attenuation with depth and transmitted power variations occurring with pulse-repetition interval modifications. Results showed statistically stronger backscattered power in veins compared to arteries for the iliac, femoral and popliteal sites. In comparison with healthy subjects, stronger powers were observed in hyperlipidemic patients for the femoral and popliteal sites. Power differences were also found between peripheral measurements. On the other hand, no difference was observed between the power measured in the carotid artery and jugular vein for both groups of individuals. Multiple linear regression analyses were performed to identify factors affecting the backscattered power. Results showed a correlation (r) of 71.2% between the Doppler power in the femoral vein and the linear combination of two parameters: an erythrocyte aggregation index S₁₀ measured with a laser scattering method, and the diameter of the vessel measured on B-mode images. Statistically significant linear correlation levels were also found between S₁₀ and the Doppler power in various vessels. In conclusion, this study showed that power Doppler differences exist in vivo in large vessels between veins and arteries of normolipidemic and hyperlipidemic individuals. The Doppler power variations were also shown to be related to erythrocyte aggregation.     

A wall-less vessel phantom for Doppler ultrasound studies

Doppler ultrasound flow measurement techniques are often validated using phantoms that simulate the vasculature, surrounding tissue and blood. Many researchers use rubber tubing to mimic blood vessels because of the realistic acoustic impedance, robust physical properties and wide range of available sizes. However, rubber tubing has a very high acoustic attenuation, which may introduce artefacts into the Doppler measurements. We describe the construction of a wall-less vessel phantom that eliminates the highly attenuating wall and reduces impedance mismatches between the vessel lumen and tissue mimic. An agar-based tissue mimic and a blood mimic are described and their acoustic attenuation coefficients and velocities are characterised. The high attenuation of the latex rubber tubing resulted in pronounced shadowing in B-mode images; however, an image of a wall-less vessel phantom did not show any shadowing. We show that the effects of the highly attenuating latex rubber vessels on Doppler amplitude spectra depend on the vessel diameter and ultrasound beam width. In this study, only small differences were observed in spectra obtained from 0.6 cm inside diameter thin-wall latex, thick-wall latex and wall-less vessel phantoms. However, a computer model predicted that the spectrum obtained from a 0.3-cm inside diameter latex-wall vessel would be significantly different than the spectrum obtained from a wall-less vessel phantom, thus resulting in an overestimation of the average fluid velocity. These results suggest that care must be taken to ensure that the Doppler measurements are not distorted by the highly attenuating wall material. In addition, the results show that a wall-less vessel phantom is preferable when measuring flow in small vessels.     

Effects of atherosclerotic lesions on ultrasonic beam and cw doppler signals

Doppler ultrasound has been shown to be a useful clinical tool in the noninvasive detection of vascular stenoses, occlusion, or plaques. The presence of atherosclerotic lesions in blood vessel walls can distort the Doppler ultrasonic signal, producing inverted or biphasic tracings. This observation, in fact, has been used frequently as a criterion for the diagnosis of plaque formation and calcification of these lesions. To define the source of this distortion, we have examined the effects of various types of atherosclerotic lesions on the transmitted ultrasonic beam generated by a continuous wave (CW) Doppler ultrasonic probe. These results are compared to the Doppler flow tracings obtained by a CW ultrasonic Doppler flowmeter from blood vessels with overlaying lesions in a mock flow system. It is concluded that severe distortion in the form of beam refraction or diffraction can be produced by calcified lesions, resulting in biphasic or inverted flow signals.     

Doppler spectral characterization of flow disturbances in the carotid with the Doppler probe at right angles to the vessel axis

This paper reports on a new method intended to detect early flow disturbances generated by small lesions, using conventional clinical instrumentation. In vitro experiments on models of stenotic vessels are presented which prove that ultrasound Doppler, with the beam directed at right angles to the vessel axis can detect vortices and other flow disturbances caused by wall irregularities. These disturbances characterized by small velocity components first toward and then away from the transducer correlate with the spectrum of vortices caused by small artificial lesions. We found these disturbances in flow to be too small to cause detectable broadening in the Doppler spectrum acquired in the traditional way (i.e. with the beam at an angle less than 90 degrees). The detected flow disturbances were found to depend on the surface roughness, the profile of the obstructive lesion and the narrowing of the vessel. Similar flow disturbances to those detected in vitro were demonstrated in vivo for this new beam orientation in regions of the carotid, such as the bulb and the beginning of the common carotid, where vortex-like flows are expected.     

Early ovarian cancer: 3-D power Doppler

Transvaginal sonography plays an important role in the assessment of the morphology of ovarian lesions. However, the accuracy of the technique is limited due to the significant number of false-positive results. Color Doppler imaging and pulsed Doppler spectral analysis enable evaluation of ovarian tumor blood flow, analysis of the distribution of blood vessels, and quantitative measurement of blood flow velocity waveforms. These parameters increase the sensitivity and specificity of ultrasound evaluation of ovarian tumors. Unfortunately, there is no consensus as to which Doppler parameters and cutoff values are the most predictive of malignancy. Three-dimensional (3-D) power Doppler ultrasound provides a new tool to evaluate features of tumor vascularity. Three-dimensional ultrasound and 3-D power Doppler imaging in patients with “positive” findings on standard ultrasound tests, which encompass annual gray-scale transvaginal sonography followed by transvaginal color Doppler ultrasound in selected cases, represent a novel approach for early and accurate detection of ovarian cancer through screening. Combined evaluations of morphology and neovascularity by 3-D power Doppler ultrasound may improve early detection of ovarian carcinoma. Contrast-enhanced 3-D power Doppler sonography facilitates visualization of adnexal tumor vessels, which may aid in differentiating benign from malignant adnexal lesions.