Evaluation of extracranial blood flow in Parkinson disease

Decreased cerebral flow velocities in Parkinsonian patients were reported previously. Because of the limited data on vascular changes in Parkinson disease (PD), which may have a vascular etiology, we aimed to disclose any possible cerebral hemodynamic alteration in Parkinsonian patients. We prospectively evaluated 28 non-demented, idiopathic parkinsonian patients and 19 age and sex matched controls with Doppler sonography. Flow volumes, peak systolic flow velocities, and cross-sectional areas of vertebral and internal carotid arteries (ICA) were measured and compared between patients and controls. Correlation of patient age and disease duration with Doppler parameters was observed; and each Doppler parameter of patients within each Hoehn-Yahr scale was compared. There was no significant difference of measured parameters between groups. No correlation was found between disease duration and age with flow volume, cross-sectional area or peak systolic velocity. Hoehn-Yahr scale was not found having significant relation with Doppler parameters. Values of vertebral, internal carotid and cerebral blood flow volumes (CBF), peak systolic velocities, and cross-sectional areas were not significantly different between Parkinsonian patients and age and sex matched controls. Although regional blood flow decreases may be seen as reported previously, Parkinson disease is not associated with a flow volume or velocity alteration of extracranial cerebral arteries.     

蒙古沙土鼠完全性脑缺血模型的研究

用４０只蒙古种沙土鼠，经双侧颈总动脉血流阻断后，采用ＪＩ－２００激光微循环动态分析仪、ＬＭＢ－１型激光微循环显微镜及其录像系统双重观察，计算机同步记录。结果显示：３８例沙土鼠脑膜微循环血流完全停止，脑局部血流量几乎降到０。但是仍有２例尚有血流，有异于一些论著有关蒙古沙土鼠“阻断双侧颈总动脉，肯定造成双侧大脑半球的完全性缺血”的报导。提示：为了保障完全性脑缺血模型的成功制作，上述现象必须引起重视。     

Perception of posture and cerebral blood flow.

The perception of posture in man is made possible by the information of the vestibular organs, the visual system, the proprioception and the blood volume distribution. The present study examined the cerebral blood flow velocity (CBFV) and the fluid volume of the thoracic cavity under different pressure conditions and their effects on the perception of posture. Changes in blood flow velocity were measured by transcranial Doppler sonography (TCD), and changes in the blood volume distribution of the upper torso were registered by impedance plethysmography. The results indicated that the cerebral blood flow volume and the thoracic blood volume changed in the same manner. Lower Body Positive Pressure (+30 mmHg) led to an increase in central volume and CBFV. During the Lower Body Negative Pressure Treatment (-30 mmHg), the central blood volume and the cerebral blood flow velocity decreased while venous pooling occurred. Additionally, the changes in both parameters were associated with an altered posture perception. The correlations between the SHP and the two physiological parameters cerebral blood flow velocity and fluid shift in the upper thorax indicate that the fluid shift in the thoracic cavity was more closely related to the SHP than to the changes in cerebral blood volume.     

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.     

血管壁面剪切应力的测量及其临床研究进展

总结血管壁面剪切应力(WSS)的几种测量技术和计算方法,主要包括基于磁共振或磁共振结合计算流体动力学(CFD)、计算机断层扫描(CT)、血管内超声、传统超声、超声向量血流成像和超声粒子流的血流速度测量技术,以及根据速度计算WSS的几种不同运算方法。介绍WSS计算时的另一个重要参数--血液黏滞系数(又称“血黏度”),描述该参数在精确测量WSS时的选取和计算。此外,通过现有文献论述三维向量WSS的测量以及WSS相关临床参数的计算方法,对现有的WSS临床研究做综述性的讨论。针对颈动脉、主动脉、冠状动脉、肱动脉、股动脉等不同血管,列举WSS相关的临床研究结果,并从中归纳出绝大多数临床研究认可的3个主要结论。     

高压氧干预交感神经型颈椎病患者椎基底动脉血流的变化

背景：交感型颈椎病病因、发病机制尚不明确,目前无明确的客观检查标准,经颅多普勒超声仪能够直接对椎-基底动脉系统进行血流动力学监测,可作为交感神经型颈椎病诊断的一项客观指标。高压氧治疗对交感型颈椎病患者椎基底动脉血流速度影响的报道较少。 目的：观察高压氧治疗对交感神经型颈椎病患者椎基底动脉血流速度及疗效的影响。 方法：将交感神经型颈椎病患者随机分为2组,观察组采用德国吕内堡医疗公司的电脑控制脉冲牵引和多人空气加压高压氧舱治疗;对照组仅采用德国吕内堡医疗公司的电脑控制脉冲牵引治疗。治疗前后均采用经颅多普勒超声仪检查右椎动脉、左椎动脉、基底动脉多普勒血流速度的变化情况。 结果与结论：观察组血流减慢41例患者在治疗后双侧椎动脉、基底动脉血流速明显增快(P < 0.01);血流增快22例患者治疗后双侧椎动脉、基底动脉血流速明显减低(P < 0.01)。对照组患者除左椎动脉收缩期血流速度及基底动脉舒张期血流速度有改变外,余无明显改变。观察组患者治愈率及总有效率显著高于对照组(P < 0.01)。提示高压氧对交感神经型颈椎病患者椎基底动脉血流速度有明显改善作用,具有双相调节性,血流速度监测可作为交感神经型颈椎病诊断和疗效判定的一项客观依据。同时高压氧是治疗交感神经型颈椎病较有效的方法。     

The use of transcranial ultrasonography to predict stroke in sickle cell disease.

BACKGROUND. Stroke, especially cerebral infarction, is a major cause of morbidity and mortality in children with sickle cell disease. Primary prevention of stroke by transfusion therapy may be feasible if there is a way to identify the patients at greatest risk. Transcranial Doppler ultrasonography can measure flow velocity in the large intracranial arteries. The narrowing of these arteries, which leads to cerebral infarction, is characterized by an increased velocity of flow. METHODS. Using transcranial Doppler ultrasonography, we prospectively measured the velocity of cerebral blood flow in children and young adults being followed because of sickle cell disease. The results were classified as either normal or abnormal on the basis of the highest velocity of flow in the middle cerebral artery. Abnormal velocity was defined as a flow greater than or equal to 170 cm per second, a definition determined by post hoc analysis to maximize the predictive success of the test. The end point was a clinically apparent first cerebral infarction. RESULTS. Two hundred eighty-three transcranial ultrasound examinations were performed in 190 patients with sickle cell disease (age at entry, 3 to 18 years). After an average follow-up of 29 months, cerebral infarction was diagnosed in seven patients. In 23 patients the results of the ultrasound examinations were abnormal, and in 167 patients they were normal. The clinical and hematologic characteristics of the two groups were similar, but six of the seven strokes occurred among the 23 patients with abnormal ultrasound results (P less than 0.00001 by Fisher's exact test). In this group, the relative risk of stroke was 44 (95 percent confidence interval, 5.5 to 346). CONCLUSIONS. Transcranial ultrasonography can identify the children with sickle cell disease who are at highest risk for cerebral infarction. Periodic ultrasound examinations and the selective use of transfusion therapy could make the primary prevention of stroke an achievable goal.     

支架置入前脑动脉瘤血流场的特性分析

BACKGROUND: Cerebral aneurysm is a kind of mortal hemangioma, and its treatments such as endovascular embolization and clipping both cause high postoperative recurrence rate and mortality. So the stent implantation for cerebral aneurysm is coming into being. OBJECTTVE: To evaluate the hemodynamic parameters after stent implantation into cerebral aneurysm and to provide a novel feasible strategy for clinical treatment. METHODS: A retrospective analysis was preformed based on the CT image data of 11 patients with cerebral aneurysm from the Affiliated Hospital of Xinjiang Medical University. Firstly, the flexible and solid model of cerebral aneurysm was established by the MIMICS and reverse engineering. Secondly, the matching stent model was implanted into the cerebral aneurysm, and then the blood flow structure of cerebral aneurysm was analyzed by the fluid dynamics theory and the Fluent with the method of two-way flow solid coupling. Finally, comparative analysis of the kinetic parameters of cerebral aneurysm before and after implantation, including wall pressure, blood velocity, path line of the blood flow, wall shear stress, wall deformation was conducted, and blood flow characteristics after stent implantation were analyzed under different entrance velocity. RESULTS AND CONCLUSION: After implantation, the wall surface pressure was reduced about 61.1%; the blood flow velocity around the stent and the inside of the cerebral aneurysm was decelerated obviously; under setting 2 000 lines of blood flow, the number of path line of blood flow into the cerebral aneurysm reduced about 75.0%, the maximum wall shear stress decreased about 79.3%, and the maximum wall deformation reduced to a lower level. The entrance velocity was respectively v1=0.1 m/s, v2=0.2 m/s, v3=0.3 m/s and the wall pressure was in a gradient ascent; the wall shear stress increased with the velocity, meanwhile, τzou (left neck of aneurysm) <τzhong (aneurysm )< τyou (right neck of aneurysm). The path lines of blood flow mainly concentrated in the top of the aneurysm, and the blood velocity markedly affected the surface deformation. These results indicate that main hemodynamic parameters are obviously improved after stent implantation into cerebral aneurysm, and the blood velocity should never be neglectful in the treatment process.     

Blood flow velocity,erythrocyte deformability and hepatic enzymes in heavy alcohol drinkers

Significantly decreased blood flow velocity in cerebral arteries, as well as decreased erythrocyte deformability, was found in heavy alcohol drinkers (Gdovinová 2002). The aim of this study was to determine if there is any correlation between the two. At the same time, the correlation between blood flow velocity and hepatic enzymes was also studied. The study group comprised 30 male patients, who were heavy alcohol drinkers, with a mean age of 46.4 years. Mean flow velocity (Vmean) was determined by a 2 MHz pulsed Doppler probe. Erythrocyte membrane biophysical properties were estimated by cation-osmotic haemolysis (COH). Hepatic enzymes [aspartate aminotransferase (AST), alanine aminotransferase (ALT) and gamma-glutamyltransferase (GMT)] were measured in the Department of Biochemistry. The results were compared with the results from 20 healthy volunteers of the same age. Differences between the two groups were tested by Students t-test, and the relationship between blood flow velocity and COH, and of hepatic enzymes was analysed by regressive and correlative analysis. Results showed that Vmean was significantly decreased in heavy alcohol drinkers, in all cerebral arteries (the middle, anterior, and posterior cerebral arteries). No differences were noted between the left and right sides of the arteries tested. COH was similarly significantly decreased in heavy drinkers, in the medium of low (15.4 mmol/l NaCl) and high (123.2 mmol/l NaCl and above) ionic strength. Linear correlation between COH and Vmean was determined by correlative analysis, and a linear relationship was found. All hepatic enzymes (AST, ALT, GMT) were significantly increased in heavy drinkers. The relationship between Vmean and GMT was tested by the regressive analysis, and between these two parameters a linear relationship was found. It was concluded that changes in blood viscosity after the drinking of alcohol disturbs blood velocity and brain perfusion, which can be a major risk factor in strokes.     

Real-time phase-contrast MRI of cardiovascular blood flow using undersampled radial fast low-angle shot and nonlinear inverse reconstruction

Velocity‐encoded phase‐contrast MRI of cardiovascular blood flow commonly relies on electrocardiogram‐synchronized cine acquisitions of multiple heartbeats to quantitatively determine the flow of an averaged cardiac cycle. Here, we present a new method for real‐time phase‐contrast MRI that combines flow‐encoding gradients with highly undersampled radial fast low‐angle shot acquisitions and phase‐sensitive image reconstructions by regularized nonlinear inversion. Apart from calibration studies using steady and pulsatile flow, preliminary in vivo applications focused on through‐plane flow in the ascending aorta of healthy subjects. With bipolar velocity‐encoding gradients of alternating polarity that overlap the slice‐refocusing gradient, the method yields flow‐encoded images with an in‐plane resolution of 1.8 mm, section thickness of 6 mm and measuring time at 3 T of 24 ms (TR/TE = 3.44/2.76 ms; flip angle, 10º; seven radial spokes per image). Accordingly, phase‐contrast maps and corresponding velocity profiles achieve a temporal resolution of 48 ms. The evaluated peak velocities, stroke volumes, flow rates and respective variances over at least 20 consecutive heartbeats are in general agreement with literature data. Copyright © 2011 John Wiley & Sons, Ltd.     

Signal-to-noise efficiency in magnetic resonance imaging

The dependence of signal-to-noise ratio (SNR) on the analog filter, the sampling rate and the number and dimensions of voxels is derived for magnetic resonance imaging (MRI). It is shown that the object signal-to-noise ratio scales directly with the voxel volume and the square root of the number of voxels. Defining an efficiency figure of merit as the SNR divided by the square root of the imaging time, it is shown that efficiency is always improved when imaging with the lowest possible resolution (largest voxel dimensions) consistent with viewing the desired anatomical detail. The results directly imply the relative efficiency of 3-D (volume), 2-D (plane), 1-D (line) and 0-D (point) imaging techniques. It is shown that spatial averaging is an inefficient method of noise reduction in MRI. As long as voxel size is maintained constant, one can image as many pixels in the readout direction as desired with no loss in SNR; that is, the number of pixels in the readout direction has no effect on the image SNR. Further, multiple sampling of each phase encoding value (to improve SNR) has no advantage over increasing the number of pixels in the phase encoding direction while leaving the voxel size constant. Some experimental observations are given.     

Cognitive performance and cerebral blood flow in essential hypotension

In the present study cerebral blood flow was assessed in 40 subjects with chronically low blood pressure and 40 normotensive controls at resting conditions and during the execution of a cued reaction time task. Blood flow velocities were recorded by means of transcranial Doppler sonography in both middle cerebral arteries. In hypotensives flow velocity at rest was reduced bilaterally. During the anticipation of the stimuli, which the subjects had to respond to, a predominantly right hemispheric increase of flow velocity was observed in both groups. This increase was significantly less pronounced in the hypotensive group. Hypotensives showed longer reaction times, and there was a negative correlation between the extent of the flow velocity increase and the reaction times. This study is the first to demonstrate a reduced cerebral perfusion and maladaption of blood flow to cognitive demands due to essential hypotension.     

经颅多普勒超声检测动脉硬化症330例结果分析

目的：探讨经颅多普勒诊断脑动脉硬化症的可行性；方法：分析３３０例临床诊断为脑动脉硬化症病人的经颅多普勒检查结果；结果：２５７例（占７７．８％）病人符合脑动脉硬化血流改变，３１例（１２．１％）血流速度增快，１５０（５８．４％）血流速度降低，１２例（４．７％）有脑动脉狭窄表现。结论：经颅多普勒是一种安全、易行、无创的脑动脉硬化症辅助诊断手段。     

Non-invasive evaluation of the conduit function and the buffering function of large arteries in man.

The purpose of this study was to validate a two-dimensional (2D) echography coupled range-gated Doppler system for the non-invasive measurement of internal diameter, blood flow velocity, and pulse wave velocity of peripheral arteries, such as the common carotid artery (CCA), femoral artery (FA), and brachial artery (BA) in man. The array of the ultrasonic system and the Doppler probe were attached and formed a fixed angle (38 degrees 30'). The artery was firstly visualized using the echo-graphic array probe in order to position the Doppler beam. Then, the range-gated Doppler system was used to measure both internal diameter and blood flow velocity with the sample volume position covering the internal diameter. Using a hydraulic device, there was an obvious correlation between the calculated and the measured velocities (r = 0.98). Normal values of diameter, blood flow velocity and blood flow were measured in 18 healthy volunteers. The means (+/- 1 standard deviation) was as follows: diameter, CCA = 0.636 +/- 0.027 cm, FA = 0.843 +/- 0.074 cm, BA = 0.302 +/- 0.052 cm; flow velocity, CCA = 19.5 +/- 2.1 cm s-1, FA = 11.4 +/- 1.2 cm s-1, BA = 6.7 +/- 1.0 cm s-1. Blood flows were as follows: CCA, 370.6 +/- 42.5 ml mn-1, FA 387.0 +/- 75.0 ml mn-1 and BA (wrist occlusion) 29.8 +/- 12.5 ml mn-1. The intra-observer reproducibilities for CCA, FA and BA were respectively: for diameter, 4.9%, 4.12% and 14.8%; for velocity, 8.9%, 10.6% and 10.2%. The inter-observer reproducibilities were respectively: for diameter, 5.6%, 5.4% and 11.3% for velocity, 6.5%, 5.7% and 6.3%. Simultaneous determinations of pulse wave velocity from blood flow velocity recording allowed estimations of the distensibility of these arteries. Finally, the coupled echo and range-gated Doppler system permitted non-invasive evaluation of blood flow calculated as the product of the vessel cross-sectional area and measured blood velocity and also of arterial compliance as the ratio of the cross-sectional area and the square of pulse wave velocity. Such estimations of the conduit and buffering functions of peripheral large arteries in man were shown to be more accurate for the common carotid and the femoral arteries than for the brachial artery.     

Deficient adjustment of cerebral blood flow to cognitive activity due to chronically low blood pressure

The present study aimed to investigate aberrances in the adjustment of cerebral blood flow to cognitive activity due to chronically low blood pressure. By means of transcranial Doppler sonography blood flow velocities in both middle cerebral arteries (MCA) were recorded during the execution of a serial subtraction task in 40 subjects with constitutional hypotension and 40 normotensive control persons. Additionally, blood pressure was continuously monitored. As a main result significant correlations between the task-induced changes in blood pressure and those in MCA blood flow velocities were found in hypotensives, but not in control subjects. The dependence of the regulation of cerebral blood flow on blood pressure points towards deficits in cerebral autoregulation in hypotension. Over the total sample the extent of the task-induced MCA flow velocity increase was positively related to cognitive performance. This underlines the importance of the adjustment of cerebral blood flow to current demands for optimal cognitive functioning.     

Minimizing the blood velocity differences between phase-contrast magnetic resonance imaging and computational fluid dynamics simulation in cerebral arteries and aneurysms

The integration of phase-contrast magnetic resonance images (PC-MRI) and computational fluid dynamics (CFD) is a way to obtain detailed information of patient-specific hemodynamics. This study proposes a novel strategy for imposing a pressure condition on the outlet boundary (called the outlet pressure) in CFD to minimize velocity differences between the PC-MRI measurement and the CFD simulation, and to investigate the effects of outlet pressure on the numerical solution. The investigation involved ten patient-specific aneurysms reconstructed from a digital subtraction angiography image, specifically on aneurysms located at the bifurcation region. To evaluate the effects of imposing the outlet pressure, three different approaches were used, namely: a pressure-fixed (P-fixed) approach; a flow rate control (Q-control) approach; and a velocity-field-optimized (V-optimized) approach. Numerical investigations show that the highest reduction in velocity difference always occurs in the V-optimized approach, where the mean of velocity difference (normalized by inlet velocity) is 19.3%. Additionally, the highest velocity differences appear near to the wall and vessel bifurcation for 60% of the patients, resulting in differences in wall shear stress. These findings provide a new methodology for PC-MRI integrated CFD simulation and are useful for understanding the evaluation of velocity difference between the PC-MRI and CFD.     

Cerebral blood flow in essential hypotension during emotional activation

Variations of blood flow velocity in the left and right middle cerebral arteries (MCA) were measured in 20 hypotensive women and 20 normotensive control subjects during emotional stimulation using functional transcranial Doppler sonography (fTDS). The emotional stimuli were composed of three series (neutral, pleasant, and unpleasant) of 20 pictures from the International Affective Picture System (IAPS). Both groups exhibited greater increases in right than left MCA blood flow during emotional stimulation. However hypotensive subjects showed smaller increases in blood flow than did normotensive controls. Furthermore hypotensives exhibited lower MCA blood flow velocity in both hemispheres at rest than did normotensives. Nevertheless the hypotensive group rated the emotional pictures as more arousing than did the control group. Results suggest a decreased blood flow, in addition to peripheral, in the central nervous system (CNS) of hypotensives, which was associated with normal emotional responses for both valence and hemispherical asymmetry, but also with a general increase of arousal levels. This dissociation might be related to an increase in anterior cerebral arteries (ACA) blood flow and/or to hypotension-mediated baroreceptors' up-regulation to the reticular system.     

Impaired cerebral and systemic hemodynamics under cognitive load in young hypotensives: a transcranial Doppler study

Reduced sympathetic outflow and deficits in cerebral hemodynamics have been considered as possible factors mediating the impaired cognitive performance in essential hypotension. However, the relationship between systemic blood pressure (BP), cerebral blood flow and cognitive functioning is still poorly understood. The present study was aimed at clarifying the physiological processes underlying cerebral and systemic hemodynamics in young hypotensives during cognitive engagement. Doppler sonography blood flow velocities in both middle cerebral arteries were measured from 17 hypotensives and 15 normotensives during a working memory task. Impedance cardiographic and BP measures were also recorded continuously. Lower increases in systolic and diastolic BP were observed in hypotensives. However, no evidence of lower sympathetic control was found for this group, as assessed by pre-ejection period. Flow velocity in middle cerebral arteries showed a lower increase in hypotensives throughout the task. Moreover, significant positive correlations between BP changes and blood flow velocities in middle cerebral arteries during the task were obtained for this group only, suggesting a less effective cerebral autoregulation. No difference was found between groups in task performance. Results suggest that during cognitive challenge hypotensives show impaired hemodynamic adjustments, both central and peripheral. However, such alterations do not directly affect cognitive performance, at least under moderate cognitive load.     

流固耦合分析颈椎生理活动对椎动脉血流动力学的影响

目的 建立椎动脉（vertebral artery, VA）流体有限元模型,进行流固耦合计算,以深入了解颈椎活动与VA血流流体力学之间生物力学关系。方法 基于正常人颈椎（C0~T1）及双侧椎动脉三维有限元模型,模拟颈椎前屈、后伸、左右侧弯、左右旋转,观察颈椎活动对VA血管壁应力的影响,并通过流固耦合计算血管壁与流体相互作用,获取血流动力学参数。结果颈椎活动过程中,VA血管壁的最大应力通常集中在两侧C2横突孔处（入颅方向的第2个弯曲）,后伸和侧弯较旋转活动时血管壁最大应变最为明显,应变比值分别为23.04%和35.5%。侧弯活动时,血管最大应力位于对侧横突孔;旋转活动时,血管应变位于同侧横突孔。颈椎活动度方面,最低流速值几乎均出现在生理活动范围的30%~40%。颈椎前屈、后伸活动时,双侧VA流速-时间变化曲线相似,且在0.5 s内,都完成了2次流速增减的循环。侧弯时,同侧VA的波峰和波谷早于对侧VA出现;而旋转时,同侧VA的波峰和波谷晚于对侧VA出现。结论 双侧VA血管壁所受应力特点、血流速-时间变化曲线等结果能与其他实验结果相互验证,并能合理解释相关临床现象。建立的VA模型将为VA相关疾病研究提供较理想的平台。