Feature discovery and classification of Doppler umbilical artery blood flow velocity waveforms

Doppler umbilical artery blood flow velocity waveform measurements are used in perinatal surveillance for the evaluation of fetal condition. There is an ongoing debate on the predictive value of Doppler measurements concerning the critical effect of the selection of parameters for the interpretation of Doppler waveforms. In this paper, we describe how neural network methods can be used both to discover relevant classification features and subsequently to classify Doppler umbilical artery blood flow velocity waveforms. Results obtained from 199 normal and high risk patients' umbilical artery waveforms highlighted a classification concordance varying from 90 to 98% accuracy.     

Intraluminal recording of cross-sectional blood velocity distribution of human ascending aorta by ultrasound Doppler technique

A pulsed Doppler ultrasound technique was used for mapping two-dimensional blood velocity profiles in the human ascending aorta during open-heart surgery. An electronic position-sensitive device was constructed and linked to an intraluminal 10 MHz Doppler ultrasound probe. From a plane perpendicular to the central direction of blood flow, velocity mapping was performed covering the entire cross-section of the ascending aorta 6–7 cm above the valve. This method is based on a sequential sampling of velocity from continuously changing locations during a stable haemodynamic period; typically velocity points are recorded from 150–300 beats. Further processing transformed data to suit a previously developed velocity distribution model for normal blood flow in the human ascending aorta, based on multiregression analyses. In this model, the time series of data from consecutive beats were computed into an average two-dimensional profile described through one cardiac cycle. This method allows high spatial resolution (1.5 mm), in addition to the high-frequency response (200 Hz) of the modified ultrasound Doppler meter. Together with the advantage of velocity directionality and minimal time interventions, this makes the method well suited for studies on normal flow conditions as well as flow velocity distribution distal to different heart valve prostheses.     

川崎病患儿冠状动脉血流储备测定与影像形态学诊断的对照研究

目的评价持续冠状动脉病变对川崎病（KD）患儿冠状动脉血液动力学的影响,探讨冠状动脉血流储备（CFR）检测在KD患儿冠状动脉病变远期随访中的应用价值。方法选择因胸痛、心悸以及各类偶发早搏的患儿为对照组,KD并发持续左冠状动脉病变患儿为KD组,均予以ATP160μg·kg^-1·min^-1持续静脉注射,共6min。运用经胸多普勒超声心动图（TTDE）检测冠状动脉左前降支（LAD）在ATP注射前后的舒张期峰值流速（PDV）及平均流速（MDV）,并通过计算比值得出相应CFR（PDV）和CFR（MDV）值。结果对照组纳入25例,CFR（PDV）和CFR（MDV）值均与年龄呈显著正相关（r=0.596,0.591,P=0.002,0.002）;〈2岁、-8岁和〉8岁组的CFR（PDV）95%参考值范围分别为≥1.22、≥1.94和≥2.22。KD组纳入8例,静息状态下PDV和MDV值分别为（50.0±15.07）cm.s^-1和（35.16±11.52）cm.s^-1,显著高于对照组（P=0.004,0.015）;而CFR（PDV）和CFR（MDV）值明显降低,分别为（1.67±0.38）cm.s^-1和（1.69±0.47）cm.s^-1（P=0.002,0.018）。与对照组比较,KD组7/8例（87.5%）患儿CFR（PDV）值显著降低。结论持续冠状动脉病变可导致KD患儿CFR值显著降低,TTDE检测患儿CFR具无创、安全和便捷的优点,对于KD冠状动脉病变的长期随访与临床诊断治疗策略的选择具有指导意义。     

Computer implementation in the reconstruction of 2-D flow velocity fields in ultrasound Doppler color imaging

Doppler color imaging can easily render flow information within the vessels and simultaneously provide anatomic information for diagnostic purposes. However, the angle dependence problem of the Doppler velocity measurement is a significant barrier for continuing progress toward quantitative clinical applications of this technology. This paper presents a method and the computer implementation for reconstruction of the 2-D flow velocity field (angle independent) in ultrasound Doppler color imaging. Formulae for deriving angle independent velocity amplitude and angle direction from the color images acquired with a linear array transducer are given. The hardware configuration of the data acquiring and processing system is described. Major considerations in the development of algorithms, especially the strategies for reducing the computation time are presented.     

基于造影图像的冠脉血流量和速度的测量算法

脉疾病严重程度可以从形态上和功能上进行评估.研究发现,从形态上检测冠脉狭窄来评估冠脉疾病严重程度存在一定的缺陷,因此,现在许多研究小组从功能性狭窄的角度来诊断冠脉疾病.从功能性角度,基于X-ray血管造影的血流和速度的测量方法具有潜在的临床重要性,是一个活跃的研究课题,它能辅助从功能性狭窄角度更准确的诊断冠脉疾病.基于造影图像从跟踪法和计算法两大类来阐述一些关于冠脉血流量和流速的关键算法.其中,跟踪法分为药团运输时间算法、从2D时间一距离参数图像上确定连续的血流速度法、造影剂遍历距离法和小滴跟踪算法四大类;计算法分为指示剂稀释法或Stewart-Hamilton方法、First-pass分布分析、逆向连续方程算法、逆质量守恒问题方法、光流法和流体连续法六大类.     

Doppler continuous-wave analysis of grafted mammary artery as a non-invasive technique for static and dynamic assessment of coronary flow in man

Summary In this paper, Doppler continuous-wave analysis of blood velocity in the internal mammary artery, anastomosed to the left coronary vascular bed in humans who have undergone myocardial revascularization, is proposed as a non-invasive technique to study coronary blood flow during physiological procedures which cause it to change. Blood velocity curves obtained in normal and anastomosed internal mammary arteries were compared during hyperventilation and the Valsalva manoeuvre. During hyperventilation, blood velocity increased in the normal mammary but not in the anastomosed artery. During the expiratory effort of the Valsalva manoeuvre, the mean blood velocity decreased in the normal mammary artery but it did not change significantly in the anastomosed artery. Variations in the mean velocity were largely prevented by simultaneous and well-balanced increases and decreases in the diastolic and systolic velocities, respectively.     

A novel active contour model for fully automated segmentation of intravascular ultrasound images: in vivo validation in human coronary arteries

The detection of lumen and media-adventitia borders in intravascular ultrasound (IVUS) images constitutes a necessary step for the quantitative assessment of atherosclerotic lesions. To date, most of the segmentation methods reported are either manual, or semi-automated, requiring user interaction at some extent, which increases the analysis time and detection errors. In this work, a fully automated approach for lumen and media-adventitia border detection is presented based on an active contour model, the initialization of which is performed via an analysis mechanism that takes advantage of the inherent morphologic characteristics of IVUS images. The in vivo validation of the proposed model in human coronary arteries revealed that it is a feasible approach, enabling accurate and rapid segmentation of multiple IVUS images.     

基于光声多普勒频谱标准偏差的自相关碳颗粒横向流速测量

为了测量与超声探头信号接收轴线相垂直的碳颗粒悬混液的流速,采用多普勒频谱的标准偏差估计频带展宽,频谱标准偏差由自相关方法计算。光声信号由波长532 nm重复频率20 Hz的脉冲激光激励,由中心频率10 MHz的聚焦超声换能器采集。碳颗粒悬混液由微量注射泵驱动,时域光声信号经希尔伯特变换为复信号后进行自相关计算,多普勒频宽的标准偏差由若干序列A扫的自相关平均得到。对比之前基于序列A扫的互相关方法,所提出方法的优点是自相关中的信号时移大小可自定义,如时移量远小于信号扫描间隔,可避免信号混叠,避免互相关中对重复频率为数千赫兹脉冲激光的需求。该方法的可行性通过测量横向流速为5.0~8.4 mm/s的碳颗粒悬混液的频谱标准偏差得到初步验证,实验结果显示信号的自相关结果在测量范围内呈现线性分布趋势。     

超声多普勒血流和管壁搏动信号的分离研究

目的针对超声多普勒血流检测中,传统的高通滤波法在滤除管壁搏动信号的同时也会滤除低频血流信号的问题,本研究提出一种以心电信号（electrocardiography,ECG）作为参考信号的自适应滤波的方法消除管壁干扰。方法包括两方面：其一,采用心电信号作为参考信号对超声多普勒信号进行自适应滤波;其二,采用多级自适应滤波并选择不同的参考信号的滤波方案。分别使用上述方法和高通滤波法对仿真的超声多普勒信号进行处理,并将结果进行比较。结果与传统的高通滤波法相比,该方法在有效抑制管壁搏动信号的同时保留一部分低频血流信号成分。结论该方法能较准确地提取出完整的血流超声多普勒信号,具有一定的临床应用价值。     

Haemodynamic changes in IUGR fetus with chronic hypoxia evaluated by fetal heart-rate monitoring and Doppler measurement of blood flow velocity

The measurement of fetal blood flow velocity and 24 h monitoring of fetal heart-rate (FHR) using a computer were performed to clarify the haemodynamics of growth-retarded fetuses with chronic hypoxia. One hundred normal-growth and 18 growth-retarded fetuses were analysed. All the growth-retarded fetuses with chronic hypoxia were characterised by abnormal blood flow velocity waveforms (with the pulsatility index in the descending aorta below the −1·0 SD and in the middle cerebral artery above the +1·0 SD for our reference range, from 100 normal-growth fetuses). In the latter, the incidence of accelerations of defined size and variability in FHR patterns showed a diurnal variation after 30 weeks' gestation. The initial change in FHR patterns during hypoxia in 11 growth-retarded fetuses, resulting in fetal distress, was a derangement of diurnal variations in FHR patterns, followed by a decrease in variability. A rapid increase in blood flow velocity in the middle cerebral artery with the advance of hypoxia was observed before the onset of distress. Maternal low-dose oxygen inhalation elicited a temporary increase in FHR variability in the growth-retarded but not in normal fetuses. Re-inhalation after 1 h elicited a similar change, suggesting that intermittent rather than continuous, oxygen inhalation may be more effective.     

Computerised multiparametric analysis from images of blood flow through frog mesenteric arterial bifurcation

A computerised multiparametric procedure is developed to analyse the images of blood flow through various locations of the mesenteric arterial bifurcation of frog. The data are recorded by a video microscopic system and, after digitisation and pre-processing, are analysed by an IBM PC/AT based image processing system to obtain erythrocyte and velocity distribution profiles by axial tomographic and image velocimetry techniques respectively. The vessel radius, haematocrit, blood flow through main and branch arteries and flow separation zones are determined from the data by various analytical procedures. In contrast to the earlier techniques the data are obtained from the same location of the vessel and thus the variability in flow parameters is minimised.     

多普勒超声观察创伤性寰枢椎不稳手术前后椎动脉血流的变化

目的探讨创伤性寰枢椎不稳患者内固定手术前后椎动脉血流的变化。方法32例创伤性寰枢椎不稳患者,其中男性22例,女性10例;年龄22～57岁,平均年龄38岁。手术前及内固定术后,均应用彩色多普勒超声测量颈椎1、2间和颈椎5、6间椎动脉血流速度、阻力指数。并对检查结果进行对比分析。结果32例创伤性寰枢椎不稳患者术前椎动脉血流39侧异常,25侧正常。内固定术后39侧异常者中35侧恢复正常,4侧无变化,3侧术前正常变为术后异常。结论创伤性寰枢椎不稳可导致椎动脉血流变化,手术复位内固定后增加了寰枢椎稳定性,可改善椎动脉血液供应。     

Temporal heterogeneity of the blood flow velocity at the middle cerebral artery in the normal human characterized by fractal analysis

The objective of this study is to characterize the temporal fluctuation of the axial blood flow velocity (BFV) at the middle cerebral artery (MCA). Biological observables such as BFV present complex oscillations. The irregularity of physiological systems may be assessed by fractal analysis by computing the fractal dimension (D_γ) and the corresponding temporal correlation (r_γ). The BFV at the MCA was registered with transcranial Doppler ultrasonography (TCD) in four adult volunteers. As fractal processes are assumed to have no absolute time scale, two time scales were compared. The digitized signal was averaged respectively at 1-s intervals and for each heart beat. D_γ and r_γ were determined using relative dispersion analysis. The results were D_γ= 1.24 ± 0.09 and r_γ= 0.45 ± 0.19 (mean ± SD) for the 1-s based time scale and D_r= 1.17 ± 0.09 and r_γ= 0.57 ± 0.20 for the heart-beat scale. We conclude that the temporal heterogeneity of the BFV at the MCA in the normal human has fractal properties. Fractal analysis of TCD data may become useful in clinical diagnosis because loss of complexity in physiological systems has been linked to senescence or disease conditions. Wide variations of the so called normal values of BFV measured by TCD have been reported. The physiological BFV fluctuations may explain, in part, the variability of values recorded during routine TCD diagnostic examinations. Our observations may also be of value for understanding the interaction of the vascular endothelium and the blood flow stream (shear stress).     

Occipital cortex activation studied with simultaneous recordings of functional transcranial Doppler ultrasound (fTCD) and visual evoked potential (VEP) in cognitively normal human subjects: Effect of healthy aging

We evaluated effect of aging, gender and eye (sighting) dominance on relationship between visual evoked flow response (VEFR) and visual evoked potential (VEP), which refers to neurovascular coupling. The VEFR was defined as a percentage increase of the ratio of mean blood flow velocity in the contralateral (according to the side of dominant eye processing) posterior cerebral artery P2 segment to those in ipsilateral middle cerebral artery from the baseline during half-field stimulation. Vasoneural coupling index (CI) was defined as “100 × VEFR/VEP P100 amplitude”. Compared to the healthy elderly subjects (n: 19; female/male: 6/13, mean age: 69.7 ± 7), younger participants (n: 28; female/male: 16/12; mean age: 31.1 ± 4.7) had significantly higher VEFR for both sides: 18.9 ± 6.7% versus 11.2 ± 6.7%, p < 0.001 and 17.3 ± 7.7% versus 11.8 ± 5.5%, p: 0.007, for the hemisphere contralateral to dominant and nondominant eye (D and ND side), respectively. Albeit absence of any correlation between their latencies, VEP and VEFR amplitudes were well correlated. However, this was significant only for younger subjects and more evident in D side. The CI was higher in young subjects compared to those in old ones (6.49 ± 2.79 versus 4.75 ± 2.35, respectively, p = 0.007). But, this age-related trend remained as borderline when sides were analyzed individually: In the young subjects CI was 5.99 ± 2.21 and 6.96 ± 3.22 for D and ND sides, while those were 4.27 ± 2.60 and 5.19 ± 2.07 in old ones. This study confirmed diminished visual evoked flow in relation with advancing age, and suggested that “weakened” neurovascular coupling (as evidenced by a decreased VEP and VEFR correlation along with decreased CI) as one of the underlying mechanisms.     

Influence of coronary venous retroinfusion and vasodilatation on regional myocardial blood flow measurement with microspheres. An analysis of ‘microsphere loss’ from ischaemic and reperfused porcine hearts

The influence of coronary venous retroinfusion and a vasoselective calcium antagonist felodipine on the microsphere loss in a porcine model of myocardial ischaemia and reperfusion was studied. Sixteen open-chest pigs underwent 45 min of myocardial ischaemia induced by occlusion of the left anterior descending coronary artery followed by 4 h of reperfusion. Either felodipine (felo-retro group, 7 nmol kg^-1, n= 6) or the corresponding amount of vehicle (vehicle-retro group, n= 5) was infused retrogradely into the coronary veins over 30 min, starting 5 min before reperfusion. In a third group, the same amount of felodipine was administered intravenously (felo-iv group, n= 5). Myocardial regional blood flow was measured with radiolabelled microspheres (ø= 15 μm) injected before ischaemia to investigate a possible loss during ischaemia. In the felo-retro group, the apparent blood flow in the ischaemic areas, expressed as a percentage of the corresponding values in the non-ischaemic areas (%-flow), were 73±15, 73±11 and 75±19 in the subendocardial, midmyocardial and subepicardial layers, respectively. The corresponding percentage flows were 64±11, 70±11 and 62±9 in the vehicle-retro group and 75±18, 77±15 and 76±11 in the felo-iv group. The differences between the groups were not satistically significant. It is concluded that in this open-chest preparation microsphere loss observed in the ischaemic and reperfused myocardium is not increased by coronary venous retroinfusion or by a concomitantly administered vasodilative agent like felodipine.