彩色多普勒超声及能量图对软组织蔓状血管瘤的诊断

目的探讨彩色多普勒超声及多普勒能量图在诊断蔓状血管瘤中的应用价值。方法对27例软组织不同部位的蔓状血管瘤行二维、彩色多普勒血流检查及多普勒能量图分析。结果蔓状血管瘤二维形态表现为呈梭形或长条状,内为网格或蜂窝样低或无回声区。相互交通。CDFI:内充满闪烁明亮的红蓝相间的彩流,或以低速静脉血流为主,或以高速低阻型动脉血流信号为主。加用能量图见血流信号极其丰富,连续性好,形成血管树样网状结构分布。乏氏试验,加压或体位改变后其大小形态及血流状态随之发生变化。结论彩色多普勒超声及能量图对蔓状血管瘤的诊断具有重要的临床应用价值。     

Two-dimensional color Doppler flow velocity profiles can be time corrected with an external ECG-delay device.

Although two-dimensional ultrasound color flow imaging is often considered to be a real-time technique, the acquisition time for two-dimensional color images may be up to 200 msec. Time correction is therefore necessary to obtain correct flow velocity profiles. We have developed a time-correction method in which a specially designed unit detects the QRS complex from the patient and creates a trig pulse that is delayed incrementally in relation to the QRS complex. This trig pulse controls the acquisition of the ultrasound images. A number of consecutively delayed images, with known incremental delay between the sweeps, can thus be stored in the memory of the echocardiograph and transferred digitally to a computer. The time-corrected flow velocity profile is obtained by interpolation of data from the time-delayed profiles. The system was evaluated in a Doppler string phantom test. With this technique it is possible to study time-corrected flow velocity profiles without the need to alter existing ultrasound Doppler equipment.     

A method for computer simulation of ultrasound doppler color flow images—II. Simulation results

A computational method of simulating Doppler color flow images has been developed. It is based on a point-scattering model of moving blood and surrounding tissue and is capable of treating the entire flow image generation process. Simulated images of parabolic flow dynamics in a cylindrical vessel are presented to show the statistical nature of the map of velocity estimates and to demonstrate the effects of wall filters and different display schemes. Quantitative results of extracted velocity profiles are included and indicate the usefulness of the simulation method for studying the quantitative capabilities of flow imaging.     

Quantification of Ultrasound Correlation‐Based Flow Velocity Mapping and Edge Velocity Gradient Measurement

This study investigated the use of ultrasound speckle decorrelation‐ and correlation‐based lateral speckle‐tracking methods for transverse and longitudinal blood velocity profile measurement, respectively. By studying the blood velocity gradient at the vessel wall, vascular wall shear stress, which is important in vascular physiology as well as the pathophysiologic mechanisms of vascular diseases, can be obtained. Decorrelation‐based blood velocity profile measurement transverse to the flow direction is a novel approach, which provides advantages for vascular wall shear stress measurement over longitudinal blood velocity measurement methods. Blood flow velocity profiles are obtained from measurements of frame‐to‐frame decorrelation. In this research, both decorrelation and lateral speckle‐tracking flow estimation methods were compared with Poiseuille theory over physiologic flows ranging from 50 to 1000 mm/s. The decorrelation flow velocity measurement method demonstrated more accurate prediction of the flow velocity gradient at the wall edge than the correlation‐based lateral speckle‐tracking method. The novelty of this study is that speckle decorrelation‐based flow velocity measurements determine the blood velocity across a vessel. In addition, speckle decor‐relation‐based flow velocity measurements have higher axial spatial resolution than Doppler ultrasound measurements to enable more accurate measurement of blood velocity near a vessel wall and determine the physiologically important wall shear.     

Velocity measurement accuracy in optical microhemodynamics: experiment and simulation

Micro particle image velocimetry (μPIV) is a common method to assess flow behavior in blood microvessels in vitro as well as in vivo. The use of red blood cells (RBCs) as tracer particles, as generally considered in vivo, creates a large depth of correlation (DOC), even as large as the vessel itself, which decreases the accuracy of the method. The limitations of μPIV for blood flow measurements based on RBC tracking still have to be evaluated. In this study, in vitro and in silico models were used to understand the effect of the DOC on blood flow measurements using μPIV RBC tracer particles. We therefore employed a μPIV technique to assess blood flow in a 15?μm radius glass tube with a high-speed CMOS camera. The tube was perfused with a sample of 40% hematocrit blood. The flow measured by a cross-correlating speckle tracking technique was compared to the flow rate of the pump. In addition, a three-dimensional mechanical RBC-flow model was used to simulate optical moving speckle at 20% and 40% hematocrits, in 15 and 20?μm radius circular tubes, at different focus planes, flow rates and for various velocity profile shapes. The velocity profiles extracted from the simulated pictures were compared with good agreement with the corresponding velocity profiles implemented in the mechanical model. The flow rates from both the in vitro flow phantom and the mathematical model were accurately measured with less than 10% errors. Simulation results demonstrated that the hematocrit (paired t tests, p = 0.5) and the tube radius (p = 0.1) do not influence the precision of the measured flow rate, whereas the shape of the velocity profile (p < 0.001) and the location of the focus plane (p < 0.001) do, as indicated by measured errors ranging from 3% to 97%. In conclusion, the use of RBCs as tracer particles makes a large DOC and affects the image processing required to estimate the flow velocities. We found that the current μPIV method is acceptable to estimate the flow rate on the condition that the measurement takes place at the equatorial plane of the vessel. Otherwise, it is not an appropriate method to estimate the shape of the velocity profile.     

BSS-based filtering of physiological and ARFI-induced tissue and blood motion

Blind source separation (BSS) for adaptive filtering is presented in application to imaging both physiological and acoustic radiation force impulse (ARFI)-induced tissue and blood motion in the common carotid artery. The collected raw radiofrequency (RF) data includes vessel wall motion, blood flow and ARFI-induced motion. In the context of these complex motion patterns, the same BSS adaptive filtering method was employed for three diverse applications: 1. clutter filtering ensembles prior to blood velocity estimation, 2. extracting small axial velocity components from noisy velocity measurements given large flow angles and 3. reducing noise in measured ARFI-induced tissue displacement profiles to enhance differentiation of local tissue structures. The filter separated physiological vessel wall motion from axial blood flow and ARFI-induced motion; successful filter performance is demonstrated in velocity estimates, color flow images and ARFI displacement profiles. The results demonstrate the breadth of applications for BSS adaptive filtering in the clinical imaging environment.     

Real-time three-dimensional color Doppler echocardiography for characterizing the spatial velocity distribution and quantifying the peak flow rate in the left ventricular outflow tract

Quantification of flow with pulsed-wave Doppler assumes a "flat" velocity profile in the left ventricular outflow tract (LVOT), which observation refutes. Recent development of real-time, three-dimensional (3-D) color Doppler allows one to obtain an entire cross-sectional velocity distribution of the LVOT, which is not possible using conventional 2-D echo. In an animal experiment, the cross-sectional color Doppler images of the LVOT at peak systole were derived and digitally transferred to a computer to visualize and quantify spatial velocity distributions and peak flow rates. Markedly skewed profiles, with higher velocities toward the septum, were consistently observed. Reference peak flow rates by electromagnetic flow meter correlated well with 3-D peak flow rates (r = 0.94), but with an anticipated underestimation. Real-time 3-D color Doppler echocardiography was capable of determining cross-sectional velocity distributions and peak flow rates, demonstrating the utility of this new method for better understanding and quantifying blood flow phenomena.     

Lateral Position-Dependent Velocity Estimation Error in Plane-Wave Doppler Ultrasound Systems

Doppler ultrasound has become a standard method used to diagnose and grade vascular diseases and monitor their progression. Conventional focused-beam color Doppler imaging is routinely used in clinical practice, but suffers from inherent trade-offs between spatial, temporal and velocity resolution. Newer, plane-wave Doppler imaging offers rapid simultaneous acquisition of B-mode, color and spectral Doppler information across large fields of view, making it a potentially useful method for quantitative estimation of blood flow velocities in the clinic. However, plane-wave imaging can lead to a substantial error in velocity estimation, which is dependent on the lateral location within the image. This is seen in both clinical and experimental plane-wave systems. In the work described in this article, we quantified this velocity error under different geometric and beamforming conditions using numerical simulation and experimental phantoms. We found that the lateral-dependent velocity errors are caused by asymmetrical geometric spectral broadening, and outline a correction algorithm that can mitigate these errors.     

主动脉瓣口血流速度空间分布形成机理研究

目的： 通过动物试验探讨主动脉瓣口血流速度空间分布的形成机理。方法： 研究对象包括１０ 只猪, 在全麻下实施开胸手术暴露心脏, 并获得左室流出道长轴切面, 使其长轴平行于超声声束方向。研究内容包括： １） 利用彩色多普勒血流成像测量主动脉瓣口血流速度空间分布扭曲程度; ２） 观察左室流出道中轴线两侧彩色血流的对称性, 判断血流会聚状态; ３） 根据二维图像测量室间隔角度。然后观察在整个射血期内上述三个指标的动态变化。结果： 主动脉瓣口血流速度空间分布状态随左室流出道内血流会聚方式变化而变化。在射血早期, 左室流出道内血流会聚方式最不对称, 大部分血流沿室间隔及左室前壁流向主动脉瓣口。相应地, 主动脉瓣口血流速度分布的扭曲程度最大, 且最大流速紧靠室间隔及左室前壁。射血中、晚期,左室流出道内血流逐渐变为呈中轴对称性地进入主动脉瓣口,此时主动脉瓣口血流速度分布变为平坦对称。然而, 从左室射血早期到中、晚期, 室间隔角度却逐渐增大。结论： 左室流出道内的血流会聚方式是决定主动脉瓣口血流速度空间分布的最重要因素。     

多普勒超声心动图测量肺动脉血流速度对判断肺动脉瓣 狭窄程度及鉴别诊断的价值

目的:探讨多普勒超声心动图测定肺协脉内血流速度对肺动脉瓣狭窄程度的判断及鉴别论断,球囊扩张和手术效果的价值.方法:用彩色多普勒超声观察心腔和肺动脉内的血流颜色变化,并用边疆多普勒超声测量肺动脉内血流速度.结果:肺动脉瓣狭窄程度与肺动脉内血流速度成正比例关系,对照手术前后肺动脉内血流速度,可估价手术效果.结论:多普勒超声在肺动脉瓣狭窄论断与鉴别论断中上有重要的价值.     

Experimental verification of color flow imaging based on wideband Doppler method

The purpose of this study is to eliminate the aliasing in color flow imaging. The wideband Doppler method is applied to generate a color flow image, and the validity of the method is experimentally confirmed. The single beam experiment is carried out to confirm the velocity estimation based on the wideband Doppler method. The echo data for the conventional pulsed Doppler method and the wideband Doppler method are obtained using a flow model, and the estimated velocity for each method is compared. The color flow images for each method are also generated using several types of flow model. The generated images are compared, and the characteristics of the imaging based on the wideband Doppler method are discussed. The high velocity beyond the Nyquist limit is successfully estimated by the wideband Doppler method, and the availability in low velocity estimation is also confirmed. The aliasing in color flow images is eliminated, and the generated images show the significance of the elimination of the aliasing in the flow imaging. The aliasing in color flow imaging can be eliminated by the wideband Doppler method. This technique is useful for the exact understanding of blood flow dynamics.     

Doppler color flow imaging

By simultaneous processing of frequency, phase, and amplitude information in the backscattered ultrasound signal, new instruments now permit the real-time display of high-resolution grey scale images of tissue combined with the simultaneous display of flow data from vessels within the scan plane. Doppler Color Flow Imaging, or DCFI, using such processing, permits blood flow direction and relative velocity to be detected and displayed in a color encoded display from throughout the ultrasound image. We have tested a new Doppler color flow imaging system over a period of two years to evaluate the carotid arteries, peripheral arteries and veins, and dialysis fistulas. In the abdomen and pelvis we have imaged blood flow to the liver, spleen, kidneys, uterus and renal transplants. Our experience in over 500 patients leads us to conclude that DCFI has significant advantages over conventional duplex Doppler sonography for blood flow evaluation. For examination of carotid and peripheral vessels, we have found DCFI to permit more rapid assessment in both normal and abnormal states. Areas of vessel narrowing or turbulent flow may be identified rapidly and accurately, and vessel orientation may be determined precisely, allowing accurate calculation of blood flow velocity from Doppler frequency shifts. The system we have used has adequate penetration and sensitivity to allow imaging of hepatic and renal blood flow and is extremely promising as a method of imaging organ perfusion and in the detection of abnormalities of perfusion that accompany disease, such as transplant rejection. Tumor vascularity may also be identified with DCFI, opening the possibility of additional clinical applications.     

组织多普勒速度图评价高血压左室心肌运动

目的探讨定量组织速度成像在评价高血压左室心肌运动方面的临床价值。方法运用彩色组织多普勒速度图对55例健康者及32例高血压患者的左室各心肌节段的速度曲线进行分析,测量舒张期左室心肌的收缩期运动速度(Vs)、舒张早期的运动速度(Ve)、舒张晚期运动速度(Va),并计算Ve/Va数值。结果正常人室壁的Vs与高血压组无显著差异,Ve明显高于高血压组(P<0.001),而Va则明显低于高血压组(P<0.001),Ve/Va明显高于高血压组(P<0.001)。高血压患者的左室心肌收缩速度曲线因病史、年龄、血压控制状况不同而形态各异,舒张期曲线以E波相似文献   

Velocity profiles in the normal human abdominal aorta: a comparison between ultrasound and magnetic resonance data

Evolving magnetic resonance (MR) procedures were utilized to validate one-dimensional ultrasonic (US) Doppler profiles in vivo on the basis of this alternative noninvasive method of assessing blood velocity. Corresponding velocity profiles were acquired by both US and MR in the abdominal aorta of 10 healthy volunteers. The ultrasound velocities recorded throughout a cardiac cycle along the anterio-posterior aortic diameter were compared to their spatial and temporal MR counterparts. Correlation coefficients ranging from 0.92 to 0.97 and regression slopes from 0.86 to 1.13 indicate a high degree of correspondence between the two modalities and increase the confidence in the fidelity of velocity profiles obtained with both procedures.     

In Vivo Lateral Blood Flow Velocity Measurement Using Speckle Size Estimation

In previous studies, we proposed blood measurement using speckle size estimation, which estimates the lateral component of blood flow within a single image frame based on the observation that the speckle pattern corresponding to blood reflectors (typically red blood cells) stretches (i.e., is “smeared”) if blood flow is in the same direction as the electronically controlled transducer line selection in a 2-D image. In this observational study, the clinical viability of ultrasound blood flow velocity measurement using speckle size estimation was investigated and compared with that of conventional spectral Doppler of carotid artery blood flow data collected from human patients in vivo. Ten patients (six male, four female) were recruited. Right carotid artery blood flow data were collected in an interleaved fashion (alternating Doppler and B-mode A-lines) with an Antares Ultrasound Imaging System and transferred to a PC via the Axius Ultrasound Research Interface. The scanning velocity was 77 cm/s, and a 4-s interval of flow data were collected from each subject to cover three to five complete cardiac cycles. Conventional spectral Doppler data were collected simultaneously to compare with estimates made by speckle size estimation. The results indicate that the peak systolic velocities measured with the two methods are comparable (within ±10%) if the scan velocity is greater than or equal to the flow velocity. When scan velocity is slower than peak systolic velocity, the speckle stretch method asymptotes to the scan velocity. Thus, the speckle stretch method is able to accurately measure pure lateral flow, which conventional Doppler cannot do. In addition, an initial comparison of the speckle size estimation and color Doppler methods with respect to computational complexity and data acquisition time indicated potential time savings in blood flow velocity estimation using speckle size estimation. Further studies are needed for calculation of the speckle stretch method across a field of view and combination with an appropriate axial flow estimator.     

Velocity pulse measurements in the mesenteric arterioles of rabbits

The axial red blood cell velocity pulse was quantified throughout its period by a high-speed video microscopy method, using images of erythrocytes moving near the microvessel axis. In 10 mesenteric precapillary arterioles (8 to 12 microm in diameter) from six rabbits, axial velocities ranged from 0.46 (the minimum of all the end diastolic values) to 4.8 mm s(-1) (the maximum of all the peak systolic values). With the velocity pulse shape properly quantified, a correct estimation of the average velocity over time can be made and hence, appropriate quantification of blood flow. Average velocity ranged between 1.14 mm s(-1) (8 microm arterioles) and 1.98 mm s(-1) (9 microm arterioles). Also, with the velocity pulse shape known, an estimation of the magnitude of the pulsation can be made by introducing Pourcelot's resistive index (RI) in the microvascular haemodynamics (diameter less than 15 microm). The results of this study reveal that RI in the precapillary arterioles is quite high ranging between 0.56 (8 microm arterioles) and 0.74 (12 microm arterioles). Observing the velocity pulse diagrams in different diameters, quantitative information is obtained for the first time on how the velocity pulse shape flattens as it proceeds to the capillary bed.     

Color Doppler artifact in anechoic regions

For color Doppler imaging, several types of signal processing are employed in order to produce acceptable images of blood flow in blood vessels while suppressing color in moving solid tissue. The processing can produce an artifact in which color may arise from noise or from tissue motion and fill anechoic regions preferentially. This artifact may complicate the differentiation of areas with blood flow from anechoic regions without flow. By using four different color Doppler ultrasound units to image a tissue-equivalent phantom containing anechoic cylinders, artifactual color resulted when gain was raised sufficiently. This color was concentrated in anechoic regions of a gray-scale image that did not contain flow. In two instruments, this artifact was only observed when the transducer was vibrated, simulating tissue motion. In these instruments, the identification of low-frequency, high-amplitude Doppler signals is used to locate moving solid tissue and so suppress color in these regions. In the other two instruments, the presence of echoes within the image suppressed the assignment of color. With both types of processing, color may appear artifactually in echo-free regions without flow, such as fluid collections. Presence or absence of flow should be confirmed by Doppler spectral analysis. An understanding of the origin and appearance of artifactual color can prevent its occurrence from detracting from the usefulness of color Doppler imaging.     

Quantitative assessment of regurgitant flow with total digital three-dimensional reconstruction of color Doppler flow in the convergent region: in vitro validation.

BACKGROUND: This study was designed to develop and test a total digital 3-dimensional (3D) color flow map reconstruction for proximal isovelocity surface area (PISA) measurement in the convergent region. METHODS: Asymmetric flow convergent velocity field was created in an in vitro pulsatile model of mitral regurgitation. Image files stored in the echocardiographic scanner memory were digitally transferred to a computer workstation, and custom software decoded the file format, extracted velocity information, and generated 3D flow images automatically. PISA and volume flow rate were calculated without geometric assumption. For comparison, regurgitant volume was also calculated, using continuous wave Doppler, 2-dimensional (2D), and M-mode color flow Doppler with the hemispheric approach. RESULTS: Flows from 3D digital velocity profiles showed a closed, excellent relation with actual flow rates, especially for instantaneous flow rate. Regurgitant volume calculated with the 3D method underestimated the actual flow rate by 2.6%, whereas 2D and the M-mode method show greater underestimation (44.2% and 32.1%, respectively). CONCLUSION: Our 3D reconstruction of color flow Doppler images gives more exact information of the flow convergent zone, especially in complex geometric flow fields. Its total digital velocity process allows accurate measurement of convergent surface area and improves quantitation of valvular regurgitation.     

Detectability of Small Blood Vessels with High-Frequency Power Doppler and Selection of Wall Filter Cut-Off Velocity for Microvascular Imaging

Power Doppler imaging of physiologic and pathologic angiogenesis is widely used in preclinical studies to track normal development, disease progression and treatment efficacy but can be challenging given the presence of small blood vessels and slow flow velocities. Power Doppler images can be plagued with false-positive color pixels or undetected vessels, thereby complicating the interpretation of vascularity metrics such as color pixel density (CPD). As an initial step toward improved microvascular quantification, flow-phantom experiments were performed to establish relationships between vessel detection and various combinations of vessel size (160, 200, 250, 300 and 360 μm), flow velocity (4, 3, 2, 1 and 0.5 mm/s) and transducer frequency (30 and 40 MHz) while varying the wall filter cut-off velocity. Receiver operating characteristic (ROC) curves and areas under ROC curves indicate that good vessel detection performance can be achieved with a 40-MHz transducer for flow velocities ≥2 mm/s and with a 30-MHz transducer for flow velocities ≥1 mm/s. In the second part of the analysis, CPD was plotted as a function of wall filter cut-off velocity for each flow-phantom data set. Three distinct regions were observed: overestimation of CPD at low cut-offs, underestimation of CPD at high cut-offs and a plateau at intermediate cut-offs. The CPD at the plateau closely matched the phantom's vascular volume fraction and the length of the plateau corresponded with the flow-detection performance of the Doppler system assessed using ROC analysis. Color pixel density vs. wall filter cut-off curves from analogous in vivo experiments exhibited the same shape, including a distinct CPD plateau. The similar shape of the flow-phantom and in vivo curves suggests that the presence of a plateau in vivo can be used to identify the best-estimate CPD value that can be treated as a quantitative vascularity metric. The ability to identify the best CPD estimate is expected to improve quantification of angiogenesis and anti-vascular treatment responses with power Doppler. (E-mail: jlacefield@eng.uwo.ca)     

运用彩色多普勒流速剖面图测定血流量的实验研究

运用实验血流模型，检测新近开发的彩色多普勒血流速度部面图（velocityprofile，VP）对血流量测定的准确性，并与脉冲型多普勒（PulsedwaveDoppler，PWD）测定法比较。结果显示在不同流速下两种方法的流量测值与实际流量间均有高度相关性，相关系数r分别为0．999（P＜0．001）和0．988（P<0．02）。但测得流量与实际流量之间的误差程度，VP法为-7.64～2．79％，PWD法为17.82～27.97％。表明VP法较PWD法更接近实际情况。