Evaluation Of Blood Flow Velocity Research Articles

Insonation angle impact on micro-Doppler evaluation in cerebrovascular surgery: technical note

Introduction: The insonation angle consideration is important in the Doppler-sonographic evaluation of blood flow velocities and volume, however, the concept is rarely applied to the intraoperatively used micro-Doppler.This technical note aims to emphasize the possibility and necessity of insonation angle correction and preservation for the blood flow assessment in cerebrovascular surgery.Methods: Bi-directional surgical Doppler with a 20MHz flexible bayonet 1.2mm diameter probe was used for the intraoperative blood flow assessment, with the variable insonation angle on the straight parts of the arteries, and the results were recorded to demonstrate the importance.Results: The measurements performed confirmed that the blood flow features, including the direction, velocity, and especially the volume, are highly susceptible to the insonation angle variations. Although there were significant alterations, positioning the probe at an angle of ~60 degrees resulted in the variable but less altering measurements.Conclusion: Positioning the probe at ~60 degrees is desirable; however, it appears that it is even more important to maintain the same insonation angle and probe position when assessing the vessels repeatedly for blood flow alterations that might occur in the course of cerebrovascular surgery.

Physics-Informed Neural Networks for Brain Hemodynamic Predictions Using Medical Imaging.

Determining brain hemodynamics plays a critical role in the diagnosis and treatment of various cerebrovascular diseases. In this work, we put forth a physics-informed deep learning framework that augments sparse clinical measurements with one-dimensional (1D) reduced-order model (ROM) simulations to generate physically consistent brain hemodynamic parameters with high spatiotemporal resolution. Transcranial Doppler (TCD) ultrasound is one of the most common techniques in the current clinical workflow that enables noninvasive and instantaneous evaluation of blood flow velocity within the cerebral arteries. However, it is spatially limited to only a handful of locations across the cerebrovasculature due to the constrained accessibility through the skull's acoustic windows. Our deep learning framework uses in vivo real-time TCD velocity measurements at several locations in the brain combined with baseline vessel cross-sectional areas acquired from 3D angiography images and provides high-resolution maps of velocity, area, and pressure in the entire brain vasculature. We validate the predictions of our model against in vivo velocity measurements obtained via four-dimensional (4D) flow magnetic resonance imaging (MRI) scans. We then showcase the clinical significance of this technique in diagnosing cerebral vasospasm (CVS) by successfully predicting the changes in vasospastic local vessel diameters based on corresponding sparse velocity measurements. We show this capability by generating synthetic blood flow data after cerebral vasospasm at various levels of stenosis. Here, we demonstrate that the physics-based deep learning approach can estimate and quantify the subject-specific cerebral hemodynamic variables with high accuracy despite lacking knowledge of inlet and outlet boundary conditions, which is a significant limitation for the accuracy of the conventional purely physics-based computational models.

Evaluation of blood flow velocity to determine the effect of fortifiers on intestinal hemodynamics

Evaluation of blood flow velocity to determine the effect of fortifiers on intestinal hemodynamics

Color Doppler to Characterize Malignant Breast Lesion

Doppler ultrasound is an important non-invasive diagnostic tool for identifying breast diseases. Ultrasound utilizes spectral Doppler techniques for quantitative evaluation of blood flow velocities, and these measurements play a crucial role in the diagnosis. In this paper, we describe a computer vision approach to automate the Doppler malignancy estimation. We present a technique for segmenting blood vessels in ultrasound color Doppler images based on image processing techniques. The technique decomposes a complex object representing either two or more vessels artificially linked together or a main vessel with its branches. We segment out the blood vessels in ultrasound color Doppler images and count the number of vessels to detect breast malignancy. MATLAB has been used to simulate the algorithm and the results obtained are presented in this paper. The result represents distinct vessels that can be used in further object recognition and quantification applications. In the last two decades of the twentieth century, a combination of modern treatment methods and strategies for early detection through screening and better public awareness, have improved survival of breast cancer despite a worldwide rise in its incidence. Different macro imaging like X-Ray mammography, Sono-mammography and Breast MRI play a major role in detection. Sono-mammography is a promising one among them for it is non-invasive and also cost effective for mass screening. Ultrasound imaging systems offer two main image types- gray-scale images and color Doppler images, each of which has its own clinical usage. Gray-scale images are used to visualize the anatomy of different body organs, while color Doppler images are used to visualize the blood flow (1) within the organs. Both images are used simultaneously for diagnosis as shown in Figure 1. To improve the accuracy of USG, additional techniques like Doppler imaging can be used. Doppler ultrasound technique is associated with reflection of continuous ultrasound waves. When an interface has back and forth movement, the transmitter and receiver frequency of the reflected ultrasound wave decreases or increases respectively. Doppler Effect refers to a change in the perceived frequency of sound emitted by a moving source. Doppler machines have the capability to note down the frequency changes. Doppler Effect in reflected wave gives information about the motion of the tissue interfaces. Transducers used for Doppler instruments consist of double-crystal, one transmitter and another receiver. Transmitter generates continuous ultrasound beam and they have no or very little damping material inside. Quantitative blood flow measurement can be done using this technique and it produces 2D images of region where blood-flow or tissue movement is occurring. The cost of this instrument is also very low.

Orbital Doppler Evaluation of Blood Flow Velocities in Patients with Diabetic Retinopathy

There have been conflicting results in relation to impaired ocular hemodynamics in the orbital vessels of patients with diabetic retinopathy (DR). Clarification of the early signs of retinopathy in diabetic patients is urgently needed. We aimed to evaluate orbital blood flow velocities using Doppler and gray-scale sonography in patients with DR, and to compare the results with those of their non-diabetic and diabetic peers without retinopathy. Orbital Doppler and gray-scale sonography were performed in 123 patients aged 29-77 who had been divided into 3 groups: non-diabetic controls (n = 25), diabetes and impaired glucose tolerance with minimal clinical retinopathy (n = 74), and diabetes with untreated non-proliferative retinopathy (n = 24). Retinopathy was diagnosed by an ophthalmologist on the basis of fundoscopic examination. The peak systolic (PSV) and end-diastolic (EDV) blood flow velocities, and the resistivity and pulsatile indices, of the ophthalmic artery, central retinal artery, posterior ciliary artery, and central retinal vein were measured. Compared with healthy controls, the age-adjusted resistivity and pulsatile indices of the ophthalmic artery were significantly higher in patients with DR (p < 0.05). PSV and EDV of the posterior ciliary arteries were significantly lower in diabetic patients with DR. After further adjustment for age, gender, HbA1c, fasting plasma glucose, blood pressure, BMI, cholesterol, HDL, LDL, and triglycerides, only the resistivity index of the ophthalmic artery and the central retinal vein remained significantly higher in patients with DR compared with healthy controls (p < 0.005 after Bonferroni adjustment). Resistivity index alteration of the ophthalmic artery and central retinal vein may be prevalent among patients with early changes in DR.

Normal values of cerebral blood flow velocities in neonates

There was used color Doppler ultrasonography (cD-USI), allowing simultaneous examination of parenchymal and vascular cerebral structures. The evaluation of blood flow velocities in cerebral arteries is important in the assessment of cerebral circulation in hypoxic-ischaemic and haemorrhagic brain damage in neonates. The aim of this study was to estimate normal values of cerebral blood flow velocities (CBFV) and Doppler indices--pulsatility index (PI) and resistance index (RI)--in the anterior cerebral artery (ACA) during the first days of life in infants. CBFV, PI and RI were obtained during the first week of life with cD-US in 70 infants divided in four groups of gestational age (GA): < or =28 gestational weeks (GW); 29-32 GW; 33-36 GW; and > or =37 GW. Infants with congenital malformations, severe perinatal asphyxia, cerebral haemorrhagic lesion, DAP or severe hypotension were excluded. The mean GA of infants was 34.5 +/- 5.5 GW (range 26-40 GW) and the mean birth weight (BW) was 2540 +/- 950 g (range 750-4000 g). In the 1st group of 10 infants, < or =28 GW, the mean BW was 950 +/- 110 g and values of RI were 0.59 +/- 0.10 and PI 1.06 +/- 0.080. In the 2nd group of 20 infants, 29-32 GW, the mean BW was 1350 +/- 290 g and values of RI were 0.60 +/- 0.10 and PI 1.10 +/- 0.15. In the 3rd group of 20 infants, 33-36 GW, the mean BW was 1950 +/- 750 g and values of RI were 0.63 +/- 0.08 and PI 1.15 +/- 0.30. In the 4th group of 20 infants, > or =37 GW, the mean BW was 3540 +/- 950 g and values of RI were 0.65 +/- 0.05 and PI 1.18 +/- 0.35. Values of CBFV progressively increase with GA and BW due to progressive increase of cardiac output, blood pressure and closing of ductus arteriosus. Values of RI and PI gradually increase with GA and BW as a result of progressive maturation and opening of vascular cerebral bed with a reduction of the cerebrovascular resistance.

Transcranial Evaluation of Blood Flow Velocity in the Basilar Artery in Rats by High Frequency Ultrasonic Doppler Technique

The possibility of recording the blood flow velocity in the basilar artery (a. basilaris) in rats through the occipital membrane by a two-channel ultrasonic Doppler system with single-element transducers was demonstrated. A. basilaris was located with a contact transducer working at a frequency of 33 MHz in two modes: pulsed and permanent. The mean blood flow velocity in narcotized male Wistar rats was 4.93+/-0.78 cm/sec. Functional loading tests (acute elevation of blood pressure and occlusion of the common carotid arteries) showed that this method allows recording dynamic characteristics of the blood flow reactions in a. basilaris with evaluation of its pulse wave pattern and analyzing their correlations with blood flow parameters in the carotid arteries using simultaneously the second (bandage) transducer.

The effects of body mass index on cerebral blood flow velocity

Obesity is a risk factor for cerebrovascular disease. We aimed to determine the effects of high body mass index (BMI) on cerebral blood flow regulation in patients with type-2 diabetes mellitus, hypertension, and stroke. We analyzed data from 90 controls, 30 diabetics, 45 hypertensives, and 32 ischemic stroke patients who underwent transcranial Doppler for evaluation of blood flow velocities (BFV) in the middle cerebral arteries (MCA) and cerebrovascular resistance (CVR) during supine rest and head-up tilt. This study was a cross-sectional analysis. We used a structural equation multiple indicators modeling to determine the effects of BMI and other background variables (age, sex, race, smoking, alcohol use, and systolic blood pressure) on cerebral BFV. Higher BMI (P = 0.02) and age (P = 0.004) were associated with lower mean BFV during baseline, independent of diagnosis of diabetes mellitus, hypertension or stroke, and after adjusting for all background variables and vessel diameters. Men, especially those with stroke, had a lower mean BFV than women (P = 0.01). CVR increased with BMI (P = 0.001) at baseline and during head-up tilt (P = 0.02), and was elevated in obese subjects (P = 0.004) compared to normal weight subjects across all groups. High BMI is associated with a reduction in cerebral BFV and increased CVR. These findings indicate that obesity can adversely affect cerebral blood flow and resistance in the cerebrovascular bed, independent of diagnosis of type-2 diabetes, hypertension or stroke. Obesity may contribute to cerebromicrovascular disease, and affect clinical functional outcomes of the older population.

Computer Vision Approach for Ultrasound Doppler Angle Estimation

Doppler ultrasound is an important noninvasive diagnostic tool for cardiovascular diseases. Modern ultrasound imaging systems utilize spectral Doppler techniques for quantitative evaluation of blood flow velocities, and these measurements play a crucial rule in the diagnosis and grading of arterial stenosis. One drawback of Doppler-based blood flow quantification is that the operator has to manually specify the angle between the Doppler ultrasound beam and the vessel orientation, which is called the Doppler angle, in order to calculate flow velocities. In this paper, we will describe a computer vision approach to automate the Doppler angle estimation. Our approach starts with the segmentation of blood vessels in ultrasound color Doppler images. The segmentation step is followed by an estimation technique for the Doppler angle based on a skeleton representation of the segmented vessel. We conducted preliminary clinical experiments to evaluate the agreement between the expert operator's angle specification and the new automated method. Statistical regression analysis showed strong agreement between the manual and automated methods. We hypothesize that the automation of the Doppler angle will enhance the workflow of the ultrasound Doppler exam and achieve more standardized clinical outcome.

Observation of Gastric Variceal Flow Characteristics by Endoscopic Ultrasonography Using Color Doppler

The aim of this study was to investigate the endoscopic color Doppler ultrasonography (ECDUS) findings of gastric varices and to determine the role of ECDUS in the diagnosis of gastric varices. Using ECDUS, we evaluated 114 patients with gastric varices found consecutively by routine upper endoscopy. We monitored the color flow images of gastric varices and perigastric collateral veins. We measured the blood flow velocity of gastric varices and the thickness of the gastric wall to submucosal gastric varices with this technique, and investigated the usefulness of ECDUS in evaluating the hemodynamics of gastric varices. Endoscopic findings of gastric varices were evaluated according to the grading system of the Japanese Research Committee on Portal Hypertension. Color flow images of gastric varices and perigastric veins were delineated in all 114 patients with ECDUS. Evaluation of blood flow velocity in the 114 gastric varices revealed velocities of 7.7-35.7 cm/s (mean 18.2 +/- 5.9 cm/s). The velocities (23.7 +/- 6.4 cm/s, N = 21) of large, coil-shaped (F3)-type gastric varices were significantly higher than those (16.7 +/- 4.9 cm/s, N = 93) of enlarged tortuous (F2)-type varices (P < 0.0001). The 114 gastric varices were at 1.0-2.2 mm (1.6 +/- 0.3 mm) of gastric wall thickness. The thickness (1.2 +/- 0.1 mm, N = 22) for red color sign (RC)- or erosion-positive varices was significantly less than that (1.7 +/- 0.2 mm, N = 92) for the negative cases (P < 0.0001). The mean velocity was 28.0 +/- 6.1 cm/s in bleeding cases (N = 4) and 17.6 +/- 5.5 cm/s in nonbleeding cases (N = 110), and the velocities of the bleeding cases were significantly higher than those of the nonbleeding cases (P < 0.001). The mean thickness of the gastric wall was 1.2 +/- 0.2 mm for bleeding cases and 1.6 +/- 0.3 mm for nonbleeding cases, and the mean wall thickness in the bleeding cases was significantly less than in the nonbleeding cases (P < 0.001). ECDUS is a useful modality for diagnosis of the hemodynamics of gastric varices and may allow the prediction of a high risk for hemorrhage.

Normal values of blood flow velocity in the terminal vein of preterm infants

Evaluation of blood flow velocity in terminal veins of both cerebral hemispheres by Doppler-sonographic measurement. The examinations were done in clinically stable, non-ventilated preterm infants between gestational weeks 29 and 36. Terminal veins were localised by colour duplex sonography, then the maximal blood flow velocity was measured by PW Doppler. Every measurement was repeated for accuracy. From the averaged data, percentiles were calculated for both cerebral hemispheres. A linear correlation between gestational age and maximal blood flow velocity in the terminal vein was seen. The maximal blood flow velocity increased from 3.2 cm/sec at 29 weeks to 4.6 cm/sec at 36 weeks. No difference could be seen between both cerebral hemispheres. Percentiles could be calculated for the blood flow velocity in the terminal vein of both cerebral hemispheres. Maximal blood flow velocity increases from 29 to 36 weeks of gestational age. Serial examination during the first days of life are a feasible tool for detecting preterm infants at risk for intracerebral haemorrhage or infarction.

The effects of venous occlusion on cerebral blood flow characteristics during ECMO

Extracorporeal membrane oxygenation (ECMO) in the newborn usually requires occlusion of a jugular vein, and frequently a carotid artery. The acute effects of jugular vein occlusion on cerebral blood flow characteristics have received little investigation. Six newborns (age range, 0 to 5 days; weight, 2.4 to 3.1 kg) were treated with venoarterial ECMO, with additional placement of a cephalic venous catheter, for meconium aspiration (4) or persistent fetal circulation (2). Doppler duplex ultrasound evaluation of blood flow velocity and resistive index (RI) in the right (RMCA) and left (LMCA) middle cerebral arteries was performed just before ECMO, immediately after ECMO onset, and at 8, 24, and 48 hours of ECMO. Arterial Po2 was maintained at 80 to 120 mm Hg, Pco2 at 35 to 45 mm Hg, and mean arterial pressure at 50 to 60 mm Hg. Flow velocity was measured with the cephalic venous catheter both open and closed. Closure of the cephalic venous cannula resulted in an abrupt, significant reduction in RMCA flow velocity and a significant increase in RI at the onset of ECMO and at 8 hours of ECMO. Opening the cannula restored the velocity and RI to normal. LMCA velocity and RI did not change with closure of the cephalic venous cannula. All infants survived ECMO, and five of the six are normal neurologically at 1 year of age. These data show that right carotid ligation alone did not change cerebral arterial blood flow velocity, but the addition of venous occlusion significantly decreased RMCA flow velocity, which was alleviated by cephalic venous drainage. After 24 hours of ECMO, this effect disappeared. This suggests that cephalic venous drainage may help prevent the neurological complications of ECMO by maintaining normal cerebral blood flow.

Color Doppler imaging of the ocular vessels.

Color Doppler imaging allows for simultaneous two-dimensional anatomical imaging and Doppler evaluation of blood flow velocity. We examined 40 normal eyes (17 males and 23 females, aged 16 to 57 years) with this technique. The color Doppler unit used in this study had a 5.0-MHz PLF-503 ST phased-array scanning head. Each vessel examination was repeated 10 times during a single session. The following peak flow velocities were found: central retinal artery, 12.5 +/- 2.4 cm/s; central retinal vein, 4.4 +/- 0.49 cm/s; posterior ciliary arteries, 14.4 +/- 2.6 cm/s; vorticose veins, 5.5 +/- 1.0 cm/s; ophthamic artery, 36.9 +/- 7.0 cm/s. Ophthalmic artery systolic and end-diastolic velocities declined as a function of age; however, these changes were not significant (systolic: r = -0.24; diastolic, r = -0.22). This noninvasive technique allows quantitative assessment of blood flow velocity in these vessels.

Einfluß einer antihypertensiven Therapie auf die Blutflußgeschwindigkeiten in extra- und intrakraniellen, hirnversorgenden Gefäßen unter Ruhebedingungen

The effect of antihypertensive treatment for 12 weeks with one of three medications (ß-Blocker, calcium channel blocker, or diuretic versus placebo) on blood flow velocities in extra- and intracranial arteries were investigated in 71 patients suffering from hypertension. Evaluation of blood flow velocities was performed for extracranial arteries with a duplex sonography system and for intracranial arteries with a pulsed transcranial Doppler. Under resting conditions all measured flow velocities as well as flow patterns and turbulences in the bulbus of the carotid bifurcation remained unchanged throughout the trial despite effective reduction of blood pressure in the verum groups. This may indicate that patients with hypertension have intact cerebral autoregulation.

Evaluation of blood flow velocity in the ascending aorta and main pulmonary artery of normal subjects by Doppler echocardiography

Blood flow velocity measurements were made in the ascending aorta and proximal main pulmonary artery of 20 adult normal subjects (12 men and eight women, age range 21 to 46 years) with the use of a commercial prototype ultrasound instrument combining a spectrum analyzer-based, pulsed Doppler velocimeter with a two-dimensional sector scanner. The sector scanner was used to produce two-dimensional images of the main pulmonary artery so that the Doppler sample volume could be placed parallel to the flow stream. A 2.25 MHz right-angle M-mode ultrasound transducer was positioned in the suprasternal notch and was used to measure blood flow velocity in the ascending aorta. There were significant differences ( p < 0.001) between the ascending aorta and main pulmonary artery (PA) in the following blood flow parameters: peak flow velocity (aorta = 92 cm/sec, PA = 63 cm/sec), average acceleration (aorta = 940 cm/sec 2, PA = 396 cm/sec 2), acceleration time (aorta = 98 msec, PA = 159 msec), deceleration time (aorta - 197 msec, PA = 172 msec), average deceleration (aorta = 473 cm/sec 2, PA = 356 cm/sec 2), and ejection time (aorta = 294 msec, PA = 331 msec). These data indicate that despite a four to five times higher arterial resistance in the systemic circuit compared to the pulmonary circuit, blood is accelerated two to three times more rapidly in the ascending aorta than in the main pulmonary artery. Also, the peak flow velocity is higher in the aorta and is achieved earlier in systole than in the pulmonary artery. In addition to providing insight into the normal physiology of flow in the great arteries, these Doppler measurements in normal subjects should provide a quantitative data base for evaluating flow velocity patterns in patients with known or suspected cardiac disorders under a variety of physiologic conditions.

Evaluation of Blood Flow Velocity in the Coronary Artery and Vein by Laser Doppler Velocimeter

Evaluation of Blood Flow Velocity in the Coronary Artery and Vein by Laser Doppler Velocimeter