Echocardiogram is vital for the diagnosis of cardiac disease. The heart has complex hemodynamics requiring an advanced ultrasound imaging mode. Cardiac ultrasound vector flow imaging is capable of measuring the actual magnitude and direction of the blood flow velocity, obtaining the quantitative parameters of hemodynamics, and then providing more information for clinical research and diagnosis. This study mainly reviewed several different vector flow imaging techniques for cardiac flow and presented the implementation difficulties, and proposed a diverging wave based high frame rate cardiac ultrasound vector flow imaging. The study discussed the limitation of current ultrasound technology used in the cardiac flow measurement, analyzed and demonstrated the specific reasons for these implementation difficulties and the potential future development.
Blood Flow Velocity ; Heart/physiology* ; Hemodynamics ; Ultrasonography

To understand the local hemodynamics of modified TF-AHCB carotid bifurcation model, using particle image velocimetry technique to measure the instantaneous velocity distribution of the model attatched to a circuit. The velocity was controlled by regulating the height of the reservoir. The working fluid consists of glycerine and water mixture with viscosity of 3.75 mPa.s similar to human blood. Instantaneous velocity fields were obtained by PIV and the shear stresses were calculated according to the velocity. The results showed that inside the model, there were a large flow separation and an anticlockwise rotating vortex on the lateral wall of ICA, The location and distance of the vortex changed with the flow velocity. The higher the flow velocity, the smaller the vortex distance, and the farther the location. The shear stresses on the lateral wall were significantly lower in all work condition. And there a low shear stress kernel when the velocity was lower than 0.839 m/s. The location of the low shear stress was just the position of atherosclerosis. The flow pattern inside the model consists of large flow separation and vortex zones. And there are low shear stress zones at the lateral wall of ICA, Where are thought to be associated with the genesis of atherosclerosis.
Blood Flow Velocity ; Carotid Arteries ; physiology ; Models, Cardiovascular ; Pulsatile Flow ; Regional Blood Flow ; physiology ; Rheology ; methods ; Stress, Mechanical

In physiology-related books, there are many relationship curves about blood flow rate in arteries and blood pressure changes with time, but there are not much explanation about such relationship. This is the very the question that the present article tries to answer. We clarified the relations between blood flow rate and blood pressure gradient using the experimental curves as the basis, using Poiseuille Law and relative knowledge of phisics and mathematics, and using analysis and reasoning. Based on the study, it can be concluded that in every course of cardiac cycle, the blood flow rate of any section in artery blood vessel is roughly synchronized with changing rate of space and time of the blood pressure, but blood flow rate is not synchronized with blood pressure.
Arterial Pressure ; physiology ; Arteries ; physiology ; Blood Flow Velocity ; physiology ; Humans ; Time

By using Doppler sensor and pressure sensor, the cerebrovascular stroke detector can be used to measure the blood flow velocity and blood pressure of the carotid artery. In this study, a variety of signal conversion and isolation processing techniques are proposed for processing and feature extraction of the output signals from the sensors. Finally, effective signal output waveforms that can be used to evaluate the cerebrovascular hemodynamics index (CVHI) are obtained, and the sound signal outputs that can reflect the change characteristics of blood flow velocity and blood pressure signals are generated, which realizes the application functional requirements of the detector.
Blood Flow Velocity/physiology* ; Cerebrovascular Circulation/physiology* ; Hemodynamics/physiology* ; Humans ; Stroke ; Technology

For the defects of interpreting the relationship between the distribution and severity of vascular stenostic disease and the low shear stress, the study focus on and explore the rules of the pressure distribution and variation downstream of the stenostic vessel with the numerical simulation and the hydrodynamic model of turbulent flow separation area for in vitro experiment. The results reveal that there is a good compatibility between the model experiment and the numerical simulation; there exists a marked pressure decrease downstream of the stenosis. And the distribution area of low pressure is similar to the characteristic distribution of the stenostic vessel diseases. The study suggested that the numerical simulation can be applied in the study of micro-flow field; the presure distribution and variatioin downstream of the stenostic vessel maybe another factor to trigger the pathogenesis of vessel stenostic diseases.
Blood Flow Velocity ; physiology ; Blood Pressure ; physiology ; Constriction, Pathologic ; physiopathology ; Humans ; Models, Biological ; Vascular Diseases ; physiopathology

In this paper the theory of autocorrelation algorithm for color flow mapping is analyzed and a new way for ultrasound color flow velocity estimation and real-time display is proposed. The method sets up a mapping table which directly relates to the dynamic display range and has only 256 entries using an inverse mapping method instead of calculating the arctangent value directly. This method is ideal for software implementation and offers an interactive way to the user for changing the dynamic range of flow velocity and thus to increasing the display resolution.
Algorithms ; Blood Flow Velocity ; Humans ; Pulsatile Flow ; physiology ; Rheology ; instrumentation ; Ultrasonography, Doppler, Color ; instrumentation ; methods

Utilizing the third-order polynomial curve fitted to the experimental data, which represents the relationship between cerebral blood flow (CBF) and mean artery blood pressure (MABP), we constructed a lumped-parameter dynamic model with 5 elements. In this model; the resistance is not constants it is determined by the fitted curve. We simulated the process of CBF autoregulation numerically by solving the govern equation of this model and got quite accurate results. Furthermore, we studied the influence of hemodynamic parameters on the CBF autoregulation by this model and proved that the characteristic resistance is the most important factor.
Blood Flow Velocity ; Blood Pressure ; physiology ; Cerebrovascular Circulation ; physiology ; Homeostasis ; Humans ; Hypotension ; physiopathology ; Models, Biological ; Oxygen ; metabolism ; Regional Blood Flow

Arteriosclerosis is one of the early characteristics of cardiovascular diseases, and pulse wave velocity (PWV) has the ability to reflect on arterial elasticity, so the accurate measurement of PWV can be of benefits for the prevention and treatment of cardiovascular diseases. There are two methods based on volume pulse waveform and based on pressure pulse waveform for taking the measurement of PWV. The precision of detection depends mainly on choosing the recording sites of PWV. There are several methods to choose the recording sites of PWV. We can get it by tangent and by low-water mark or culmination. We also can choose the recording sites of PWV by getting the point where the greatest slope stands. The advantages and limitations of the existing methods are analyzed in this article, and the relative research orientation in the world is addressed. Lastly a scheme for improving the detection method is presented.
Algorithms ; Arteries ; physiopathology ; Arteriosclerosis ; diagnosis ; Blood Circulation ; Blood Flow Velocity ; physiology ; Humans ; Pulsatile Flow ; physiology ; Pulse ; Signal Processing, Computer-Assisted

Blood Flow Velocity ; physiology ; Female ; Humans ; Male ; Ophthalmic Artery ; physiology ; Ultrasonography, Doppler, Transcranial ; methods

To study the blood flow parameters for 2 anatomical segments of posterior cerebral artery (PCA) in normal singleton fetal.
 Methods: The blood flow velocity parameters peak systolic velocity (PSV), end diastolic velocity (EDV), time-average maximum velocity (TAMAXV), velocity time integral (VTI) and resistance parameters systolic peak velocity and end diastolic velocity ratio (S/D), pulsatility index (PI), resistance index (RI) for 2 anatomical segments in PCA were recorded. The first segment of the PCA (PCAS1) was recorded between the origin of PCA and the proximal part of the posterior communicating artery. The second segment of the PCA (PCAS2) was recorded at the distal part of the posterior communicating artery. The blood parameters in both PCAS1 and PCAS2 were analyzed by using Pearson correlation and multiple curves fitting with gestational age (GA). Paired student's t test was performed to compare the difference in blood parameter between PCAS1 and PCAS2.
 Results: The blood flow velocity parameters in both PCAS1 and PCAS2 were increased with the GA (P<0.0001), with the best fitted curves of Quadratic curve (P<0.0001). There were no correlations between resistance parameters in PCA and GA (P>0.05). Resistance parameters in PCAS1 were higher than those in PCAS2 (P<0.05).
 Conclusion: The blood flow velocity parameters in both PCAS1 and PCAS2 are increased with GA. The resistance parameters in both PCAS1 and PCAS2 do not change with GA. Study on the velocities and resistance in these 3 arterial branches provides a more comprehensive evaluation on the process of brain circulation.
Blood Flow Velocity ; physiology ; Diastole ; physiology ; Female ; Gestational Age ; Hemodynamics ; physiology ; Humans ; Posterior Cerebral Artery ; physiology ; Pregnancy ; Systole ; physiology