Previous studies have shown that myocardial ischemia results in changes in the pattern of flow through the mitral valve (1-6). These changes in transmitral flow velocity pattern are most likely determined by disease-induced changes in the underlying diastolic properties of the heart (3,6-8). Knowing which diastolic properties determine the transmitral flow velocity pattern and how interactions between diastolic properties modify the overall transmitral flow velocity pattern would be helpful in understanding the hemodynamics of patients with myocardial ischemia.. Several transmitral flow velocity patterns have been reported during myocardial ischemia (5,6,8-10). In one pattern, early flow velocity is decreased, deceleration time is increased, and late flow velocity is increased (5,6,8). The diastolic determinant changed in this pattern is left ventricular relaxation, which is slowed. Slowed left ventricular relaxation is observed in some patients with dilated cardiomyopathy (11,12)and coronary ...
It has previously been demonstrated that predictable changes occur in mitral flow velocities under different loading conditions. The purpose of this study was to relate changes in pulmonary venous and mitral flow velocities during different loading conditions as assessed by transesophageal echocardiography in the operating room. Nineteen patients had measurements of hemodynamics, that is, mitral and pulmonary vein flow velocities during the control situation, a decrease in preload by administration of nitroglycerin, an increase in preload by administration of fluids, and an increase in afterload by infusion of phenylephrine. There was a direct correlation between the changes in the mitral E velocity and the early peak diastolic velocity in the pulmonary vein curves (r = 0.61) as well as a direct correlation between the deceleration time of the mitral and pulmonary venous flow velocities in early diastole (r = 0.84). This indicates that diastolic flow velocity in the pulmonary vein is determined ...
This thesis aims to evaluate the blood flow velocity in the Brachial artery during reactive hyperemia. Primarily to appraise the information it might contain regarding cardiovascular function and cardiovascular risk.. Ultrasonographic doppler measurements of the Brachial artery were made on the 1016 men and women aged 70 included in the prospective investigation of the vasculature in Uppsala seniors (PIVUS) study. Analysis of the blood flow velocity in the forearm was made in comparison to established methods of estimating endothelial function, clinical markers of cardiovascular risk, the Framingham risk score and global atherosclerosis determined by whole body magnetic resonance angiography.. Systolic blood flow velocity was positively related to cardiovascular risk whereas the diastolic velocity was inversely correlated. However, the systolic to diastolic blood flow velocity (SDFV) ratio was more closely associated with cardiovascular risk than its components apart.. Ultrasonographic markers ...
We quantitated phasic epimyocardial microcirculatory coronary blood flow velocity patterns in the beating left ventricle. Using a newly developed floating objective and high-speed cinematography, red cell velocities in small arterioles, capillaries, and small venules and microvascular diameters in the superficial layer of the epimyocardium of beating left ventricle were determined throughout the entire cardiac cycle in open-chest anesthetized dogs. Heart rate was maintained at 140 beats/min by means of left atrial pacing. Peak red cell velocity was observed in midsystole in small arterioles and capillaries, and in late systole in small venules. Abrupt decline in red cell velocity and, in many cases, a momentary cessation or reverse of flow, was observed in these microvessels during the pre-ejection period. The internal diameter of small venule was increased in late systole, while that of small arteriole remained almost constant during the cardiac cycle. Furthermore, in these epimyocardial ...
Doppler ultrasound was used to measure blood flow velocity in the anterior cerebral artery of six premature infants with posthaemorrhagic hydrocephalus, before and after intermittent cerebrospinal fluid (CSF) drainage, on 23 occasions. There was a significant increase in mean blood flow velocity after the drainage procedures (+5.6 cm/s, 95% confidence interval +2.9 to +8.3 cm/s), which was accompanied by a decrease in velocity waveform pulsatility. CSF pressure also fell significantly. In patients with posthaemorrhagic hydrocephalus, intermittent CSF drainage was associated with acute changes in cerebral haemodynamics.. ...
Background and purposeCerebral hyperperfusion has been related to the risk of intracranial hemorrhage (ICH) in stroke patients after vessel recanalization therapy. We hypothesized that after successful mechanical thrombectomy for acute a ...
The ability of pulsed Doppler echocardiography to identify patients with left ventricular systolic dysfunction was evaluated in 12 patients with dilated (congestive) cardiomyopathy. A range-gated, spectrum analyzer-based Doppler velocimeter was used to record blood flow velocity in the ascending aorta and main pulmonary artery. The following blood flow velocity parameters were measured or derived: peak flow velocity, acceleration time, average acceleration, deceleration time, average deceleration, ejection time, and aortic flow velocity integral. Doppler blood flow velocity data in the cardiomyopathy patients were compared to data from 20 normal subjects. Measurements from the ascending aorta revealed that peak aortic flow velocity discriminated between cardiomyopathy patients (mean 47 cm/sec, range 35 to 62) and normal subjects (mean 92 cm/sec, range 72 to 120) with no overlap in data (p , 0.001). Aortic flow velocity integral was also able to separate the patients with dilated cardiomyopathy ...
Maintaining a constant cerebral blood flow during a change in cerebral perfusion pressure is known as autoregulation. The integrity of this phenomenon is considered to be important in preventing cerebral lesions in preterm infants. A study was carried out using Doppler ultrasound measurements of cerebral blood flow velocities (CBFV) as an indicator of alterations in cerebral haemodynamics. CBFV were recorded on a beat to beat basis over 60 second epochs, during which time the cerebral perfusion pressure was changed by rapidly altering the infants posture from horizontal to either 20 degrees head up or head down. An informative response in CBFV was considered to be either (a) a uniphasic, immediate, passive alteration in velocity occurring with the change in posture and without a subsequent change or (b) a biphasic response of an initial change in CBFV followed within 20 seconds by a second response. This latter response is considered to be consistent with autoregulatory activity. A total of 501 ...
How is Mitral Flow Velocity Pattern abbreviated? MFVP stands for Mitral Flow Velocity Pattern. MFVP is defined as Mitral Flow Velocity Pattern very rarely.
1. Peak blood flow acceleration measured in the common carotid artery was compared with peak flow acceleration measured in the ascending aorta of three baboons.. 2. The response to occlusion for 60 s of the circumflex branch or the anterior descending branch of the left coronary artery was investigated.. 3. Both accelerations decreased approximately to the same extent. Peak aortic flow velocity, stroke volume and cardiac output also decreased but to a smaller extent.. 4. It is concluded that peak aortic flow acceleration is a sensitive index of myocardial function during acute coronary occlusion in conscious primates and that peak carotid flow acceleration is an indirect measure of myocardial performance under the same conditions.. ...
Purpose: : Fundus imaging is essential for diagnosing and monitoring common ophthalmic and systemic diseases. The Retinal Function Imager (RFI) is a non-invasive, easy to use, direct qualitative and quantitative imaging method that extends the utility of fundus imaging by providing quantitative information about retinal blood flow velocity. It can also be used for blood oximetry, capillary bed topography, and examining the metabolic state of the retina. Here we concentrated on characterizing blood flow velocity in retinal arteries and veins and accomplishing a nearly two-fold reduction of the variance of blood-flow velocity measurements by coupling the measurement to the heartbeat-cycle. Methods: : One eye of each of 14 healthy volunteers (mean age 30.7 years) was tested. Each subject had at least two separate sessions of imaging using the RFI. Results: : The mean velocity in non-heartbeat synchronized subjects was 6.1± 2.4 mm/sec for secondary and tertiary macular artery segments, and 4.4 ± ...
1] Parallel MRI with extended and averaged GRAPPA kernels (PEAK-GRAPPA): optimized spatiotemporal dynamic imaging. Jung B et al, J Magn Reson Imaging. 2008 Nov;28(5):1226-32. doi: 10.1002/jmri.21561. [2] J.N. Cohn, A.A. Quyyumi, N.K. Hollenberg, and K.A. Jamerson. Surrogate markers for cardiovascular disease. Circulation, 2004,109:31-46. [2] J. M. Tyszka, D. H. Laidlaw, J. W. Asa, and J. M. Silverman. Three-dimensional, time-resolved (4d) relative pressure mapping using magnetic resonance imaging. J Magn Reson Imaging, 12(2):321-329,2000 [3] 4D flow magnetic resonance imaging in bicuspid aortic valve disease demonstrates altered distribution of aortic blood flow helicity Lorenz R et al, Magn Reson Med. 2013 May 28. doi: 10.1002/mrm.24802. [4] H.G. Bogren et al. 4D magnetic resonance velocity mapping of blood flow patterns in the aorta in young vs. elderly normal subjects. J Magn Reson Imaging, 1999; 10(5):861-869.. [5] M.H. Buonocore et al. Analysis of flow patterns using MRI. International ...
Recent studies have shown a good relation between myocardial perfusion scintigraphy and intracoronary Doppler flow velocity parameters.8-11 15 However, the results are not uniform regarding both the best cut off values for the distal coronary flow reserve as well as the agreement between the invasive intracoronary diagnostic technique and non-invasive myocardial perfusion scintigraphy. Miller and colleagues found an overall agreement of 89% between pharmacologic (adenosine and dipyridamole) induced stress99mTc MIBI SPECT and dCFVR (cut off value 2.0) in a cohort of patients with single and multivessel disease.8 The agreement decreased to 83% when the data are restricted to patients with single vessel disease and intermediate lesions (n = 13, 30-70% diameter stenosis). Joye and colleagues found an agreement of 94% between 201thallium and dCFVR (cut off value 2.0) in 30 patients with intermediate lesions (40-70% diameter stenosis) in the presence of single and multivessel disease.9 ...
The hemodynamics of 56 femorodistal saphenous vein bypasses (in situ [n = 53] or reversed [n = 3]) identified to have residual or recurrent graft stenoses were characterized with Doppler-derived blood flow velocity and resting limb systolic pressure measurements. The magnitude and configuration of the graft blood flow velocity waveform were the best predictors of graft stenosis. Transformation of the graft blood flow velocity waveform from a triphasic to a monophasic or biphasic configuration coupled with a low (less than 45 cm/sec) or decrease (greater than 30 cm/sec) in peak systolic blood flow velocity relative to initial postoperative levels reliably predicted the presence of a remote occlusive lesion. In 20 (36%) of the 56 limbs, the ankle-brachial systolic pressure index (ABI) did not identify graft stenosis. The low sensitivity of ABI in the identification of graft stenosis was due to insignificant decrease (less than 0.15) of ABI (n = 11), incompressibility of the tibial arteries (n = 6), or
This paper describes the design and implementation of a two-phase flow meter which can be used in solids-in-water two phase pipe flows to measure the in-situ volume fraction distributions of both phases, the velocity profiles of both phases and the volumetric flow rates for both phases. The system contains an Impedance Cross Correlation (ICC) device which is used in conjunction with an Electromagnetic Velocity Profiler (EVP). Experimental results were obtained for the water and solids velocity and volume fraction profiles in upward inclined flow at 30 degrees to the vertical, in which non-uniform velocity and volume fraction profiles occur.. ...
Background- Lack of high-fidelity simultaneous measurements of pressure and flow velocity distal to a coronary artery stenosis has hampered the study of stenosis pressure drop-velocity (ΔP-v) relationships in patients.. Methods and Results- A novel 0.014-inch dual-sensor (pressure and Doppler velocity) guidewire was used in 15 coronary lesions to obtain per-beat averages of pressure drop and velocity after an intracoronary bolus of adenosine. ΔP-v relations from resting to maximal hyperemic velocity were constructed before and after stepwise executed percutaneous coronary intervention (PCI). Before PCI, half of the ΔP-v relations revealed the presence of a compliant stenosis, which was stabilized by angioplasty. Fractional flow reserve (FFR), coronary flow reserve (CFVR), and velocity-based indices of stenosis resistance (h-SRv) and microvascular resistance (h-MRv) at maximal hyperemia were compared. Stepwise PCI significantly lowered h-SRv, with an initial marked reduction in hyperemic ...
Techniques for the noninvasive evaluation of carotid artery disease are evolving so rapidly that a study such as this meta-analysis by Blakeley and colleagues is in danger of becoming outdated almost as soon as it is published. Nevertheless, this high-quality review synthesizes the current evidence in this field and yields useful information about the test properties of these diagnostic imaging procedures. At present, 2 noninvasive tests are clearly of value to clinicians. Duplex color ultrasonography combines anatomic B-mode views of the carotid bifurcation with Doppler blood flow velocity measurements and is the first test done in most patients suspected of having carotid disease. If substantial (, 70%) stenosis is not found, no further tests are usually necessary. If the results are positive, magnetic resonance angiography is useful for identifying additional vascular lesions and assessing the run-off circulation to the brain. The sensitivity and specificity of these 2 tests are so high that ...
Sixty post-stroke patients were randomly assigned to receive 15 sessions of the usual rehabilitation programme with or without tACS. The NIH Stroke Scale (NIHSS) and the mean blood flow velocity (MFV) and Gosling pulsatility index (PI) captured for the middle, anterior, and posterior cerebral artery were the outcome measures.. Fifteen 30-minute sessions of tACS appear to be effective for enhancing post-stroke patients neurological function. The haemodynamic measures taken indicated that the regaining of function among the patients was largely attributed to a lowering of the vascular autoregulatory activity together with an increase in blood flow velocity at the middle cerebral artery. Future studies should explore the underlying mechanisms mediating the positive effects brought about by tACS in post-stroke rehabilitation. ...
Computer Analysis of Coronary Doppler Flow Velocity: 10.4018/978-1-59904-889-5.ch038: The coronary flow reserve (CFR) represents an important functional parameter to assess epicardial coronary stenosis and to evaluate the integrity of coronary
To the Editor: Steinke and coworkers1 recently reported on the possible advantages of power Doppler imaging (PDI) for quantification of stenoses of the internal carotid artery (ICA): similar to angiography, it should be possible to assess the degree of stenosis of the ICA as the percentage of the diameter reduction from the longitudinal image.. We have tested this examination procedure by comparison with the usual, validated sonography criteria on 40 cases of ICA stenosis. Included in the observation period of the study were all consecutive stenosis findings for which color-coded duplex sonography (CCDS) fulfilled the following criteria: (1) detection of a local flow acceleration in the ICA, (2) peak flow velocity of ≥1 m/s (measurement of the jet flow at the stenosis maximum or, in cases of sound extinction there, directly distal from it), and (3) detection of flow disturbances. Quantification was achieved using the known Doppler criteria.2 In 22% of the cases an adequate evaluation by PDI ...
The flow of air passing through an orifice meter with a beat ratio (beta) of 0.75 and a Reynolds number of 54.700 has been examined using a 3-D laser Doppler velocimeter. The quantities derived from the 4096 simultaneous measurements of three velocity components at each of 670 locations in the flow field include the mean velocity vector, rms fluctuating components, the Reynolds stress tensor, and the entire triple correlation third order tensor. The mean velocity vector field shows the characteristics of flow associated with an orifice meter: fully developed axisymmetric flow undergoe, a large inward radial velocity gradient upstream of the plate. separates from the lip of the plate to form the vena contracts then spreads to the reattachment point at 2.5 pipe radii (10 step heights) downstream. The contour plots of the Reynolds stresses show the anisotropic nature of the flow field in the orifice plate region, and the triple velocity correlations indicate how rapidly the normal and shear stresses return
immediate identification and evaluation of blood flows intraoperatively.. The essential and cost effective intraoperative microvascular instrument that provides you with the sound information you need.. The VTI 20 MHz Microvascular Doppler System was specifically designed for use by surgeons who have a need to interrogate the microvascular vessels. This audio blood flow detector allows for real-time, intraoperative assessment of vessels in a wide variety of surgical specialties.. The System is ideal for intraoperative use in neurosurgical procedures. Combining a miniature probe tip with a high operating frequency, the system emits a tightly focused signal with a shallow depth of signal penetration, imparting a level of precision essential for the neurosurgeon. The sterile- out-of-the-package, single-use probes - optimize patient safety and eliminate probe failure due to reprocessing. ...
Summit Doppler LifeDop 250 Obstetrics / Vascular Doppler Combinations; hand held doppler system; includes popular probe combinations
A dependence on the position of the vessel relative to the location of the placenta was seen. Significant differences were noted when all subgroups were compared (Fig. 17). 1Sl). 27 L-.. 001 n = 71 n = 69 fZB- ~ Internal placental border External placental border ® 0 n = 27 Distant from placenta o Fig. 17. 2 Reproducibility The means and the relative coefficient of variation for the 67% and 90% confidence limits for fetal and uteroplacental blood flow parameters are presented in Table 9. Parameters with a low coefficient of variation show little dispersion about the mean and are most readily reproducible. The median value decreased from 290 ml/kg per minute in pregnancy week 24/0 to 220 mljkg in pregnancy week 40/0 (Fig. 39). - Ratio of mean blood flow volume of fetal common carotid artery to estimated fetal weight showed a decreasing trend until pregnancy week 38/0, followed by a slight increase. The median value changed from 60 ml/kg per minute in pregnancy week 28/0 to 46 ml/kg in ...
Figure 1 presents an en face plane from an age related macular degeneration (AMD) patient. It shows the removal of bias for flow estimation (grayscale is normalized to the highest flow). a) was processed with the method of direct calculation and b) with the MAP estimator. The backstitched scan pattern can be seen in the bias due to gradual changes in the background noise caused by revisitation error (i.e. the error in rescanning the same location). This induced an offset in method a) but the MAP estimator could isolate the flow from it. Figure 2 shows quantitative flow in the same en face plane processed with the MAP estimator to provide flow velocities. The determined flow velocities are within the expected range for retinal capillaries of 0.2 to 3.3 mm/s.. ...
Blood flow measurement using an improved surface integration of velocity vectors (SIVV) technique was tested in in vitro phantoms. SIVV was compared with true flow (12-116 mL/s) in a steady-state model using two angles of insonation (45 degrees and 60 degrees ) and two vessel sizes (internal diameter = 11 and 19 mm). Repeatability of the method was tested at various flow rates for each angle of insonation and vessel. In a univentricular pulsatile model, SIVV flow measured at the mitral inlet was compared to true flow (29-61 mL/s). Correlation was excellent for the 19-mm vessel (r(2)= 0.99). There was a systematic bias but close limits of agreement (mean +/- 2 SD = -24.1% +/- 7.6% at 45 degrees; +16.4% +/- 11.0% at 60 degrees ). Using the 11-mm vessel, a quadratic relationship was demonstrated between between SIVV and true flow (r(2) = 0.98-0.99), regardless of the angle of insonation. In the pulsatile system, good agreement and correlation were shown (r(2) = 0.94, mean +/- 2 SD = -4.7 +/- ...
Neurosurgery. 2010 Sep;67(3 Suppl Operative):ons102-7; discussion ons107. doi: 10.1227/01.NEU.0000383152.50183.81. Clinical Trial
Dynamic cerebral autoregulation (DCA) capacity along with the degree of internal carotid artery (ICA) stenosis and characteristics of the plaque can also play an important role in selection of appropriate treatment strategy. This study aims to classify the patients with severe ICA stenosis according to preoperative state of DCA and to assess its dynamics after surgery. Thirty-five patients with severe ICA stenosis having different clinical type of disease underwent reconstructive surgery. DCA was assessed with transfer function analysis (TFA) by calculating phase shift (PS) between Mayer waves of blood flow velocity (BFV) and blood pressure (BP) before and after operation ...
An experimental smartphone app might be an effective alternative to a traditional method of assessing circulation in people who need surgery to restore normal blood flow to the heart, a small study suggests.
The main reason for improvement or disappearance of peristent ulceration is considered to be due to clot formation outside the stent. This is promoted by stasis of the blood flow in the space between the stent and the irregular surface of the ulcer, because the stent struts decrease the blood flow into and out of the space. In addition, clot formation outside a stent is also accelerated by the decreasing of turbulent flow due to the decreased and normalized blood flow velocity at the stenotic lesion by stent placement.13-15 Neointimal hyperplasia and continuous expansion of a stent after stent placement may have the effect of curing ulcers in cases of small or shallow ulceration.. Ischemic stroke might be expected due to peristent ulceration because carotid plaque surface irregularity is considered to be one of the risk factors for microemboli, which may subsequently cause ipsilateral ischemic symptoms.8 Rothwell et al studied 3007 patients with carotid plaques in the European Carotid Study ...
TY - GEN. T1 - Efficient focusing scheme for transverse velocity estimation using cross-correlation. AU - Jensen, Jørgen Arendt. PY - 2001. Y1 - 2001. N2 - The blood velocity can be estimated by cross-correlation of received RE signals, but only the velocity component along the beam direction is found. A previous paper showed that the complete velocity vector can be estimated, if received signals are focused along lines parallel to the direction of the flow. Here a weakly focused transmit field was used along with a simple delay-sum beamformer. A modified method for performing the focusing by employing a special calculation of the delays is introduced, so that a focused emission can be used. The velocity estimation was studied through extensive simulations with Field II. A 64-elements, 5 MHz linear array was used. A parabolic velocity profile with a peak velocity of 0.5 m/s was considered for different angles between the flow and the ultrasound beam and for different emit foci. At 60 degrees ...
In spectral Doppler mode, the sample volume is placed at the end of the valvular funnel so as to minimize valvular noise and optimize the recording of blood flow. • Fig. 2-10 Spectral pulsed wave Doppler of the transaortic blood flow obtained from a left apical 5 chambers view by placing the sample volume at the level of the aortic valve. Note the asymmetry of the flow with a short acceleration time. Measurements include the maximal flow velocity (Vmax); the maximal (peak) pressure gradient (peakPG); the area under the curve, or the velocity-time integral (VTI), allowing the calculation of the mean pressure gradient (meanPG); and ejection time (ET). The aortic ratio is frequently used to describe the dimensions of the left atrium. Views Several views may be used to study the aorta and the left atrium (LA): the right parasternal long axis 5 and 4 chambers and the right parasternal short axis transaortic views. Right Parasternal Long Axis 5 Chambers View This view allows the measurements in TM ...
Cerebral autoregulation is a complex physiological process composed of both fast and slow components that may respond differently to different rates and patterns of blood pressure variation. To assess the temporal nature of autoregulation, transcranial Doppler velocity recordings of the middle cereb …
Authors:Connolly M, He X, Gonzalez N, Vespa P, Distefano J 3rd, Hu X.. Due to the inaccessibility of the cranial vault, it is difficult to study cerebral blood flow dynamics directly. A mathematical model can be useful to study these dynamics. The model presented here is a novel combination of a one-dimensional fluid flow model representing the major vessels of the circle of Willis (CoW), with six individually parameterized auto-regulatory models of the distal vascular beds. This model has the unique ability to simulate high temporal resolution flow and velocity waveforms, amenable to pulse-waveform analysis, as well as sophisticated phenomena such as auto-regulation. Previous work with human patients has shown that vasodilation induced by CO2 inhalation causes 12 consistent pulse-waveform changes as measured by the morphological clustering and analysis of intracranial pressure algorithm. To validate this model, we simulated vasodilation and successfully reproduced 9 out of the 12 pulse-waveform ...
Authors:Connolly M, He X, Gonzalez N, Vespa P, Distefano J 3rd, Hu X.. Due to the inaccessibility of the cranial vault, it is difficult to study cerebral blood flow dynamics directly. A mathematical model can be useful to study these dynamics. The model presented here is a novel combination of a one-dimensional fluid flow model representing the major vessels of the circle of Willis (CoW), with six individually parameterized auto-regulatory models of the distal vascular beds. This model has the unique ability to simulate high temporal resolution flow and velocity waveforms, amenable to pulse-waveform analysis, as well as sophisticated phenomena such as auto-regulation. Previous work with human patients has shown that vasodilation induced by CO2 inhalation causes 12 consistent pulse-waveform changes as measured by the morphological clustering and analysis of intracranial pressure algorithm. To validate this model, we simulated vasodilation and successfully reproduced 9 out of the 12 pulse-waveform ...
TY - JOUR. T1 - In Vitro verification of multiple-receiver doppler ultrasound for velocity estimation improvement. AU - Hallac, Rami R.. AU - Agarwal, Mangilal. AU - Jones, Steven A.. PY - 2010/6/1. Y1 - 2010/6/1. N2 - The coherent scattering effect, which introduces noise in Doppler-derived velocity estimates, is caused by constructive and destructive interference of sound waves scattered from multiple particles. Because the phase relationship between signals scattered from different particles depends on the orientation of the receiver, the error in a given velocity estimate depends on the receiver location. To examine this dependence, the velocity of a steady uniform flow was measured simultaneously with a transceiver and three receivers, and the cross-correlation coefficients between velocity estimates for pairs of crystals were calculated. The velocity estimates were nearly independent, with cross-correlation coefficients of approximately 0.2. This result agrees with our previously published ...
An epicardial multifunctional probe has been designed to measure blood flow velocity and muscle thickening with two sensors. The probe is implantable and remains inside the patient after surgery. The probe is removable through a small opening in the patients chest.
Correlation between aortic velocity time integral (AoVTI) at Adaptive CRT and echo-optimized device settings (AoVTI is an echocardiographic representative of stroke volume and cardiac performance ...
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In this paper, we determined the optimal flow rate trajectory during the loading phase of a mAb capture column. For this purpose, a multi-objective function was used, consisting of productivity and resin utilization. Several general types of trajectories were considered, and the optimal Pareto points were obtained for all of them. In particular, the presented trajectories include a constant-flow loading process as a nominal approach, a stepwise trajectory, and a linear trajectory. Selected trajectories were then applied in experiments with the state-of-the-art protein A resin mAb Select PrismATM, running in batch mode on a standard single-column chromatography setup, and using both a purified mAb solution as well as a clarified supernatant. The results show that this simple approach, programming the volumetric flow rate according to either of the explored strategies, can improve the process economics by increasing productivity by up to 12% and resin utilization by up to 9% compared to a ...
Level of Blood Flow  The normal blood flow to the brain is about 50 mL/100g of brain tissue/min.  Ischemic penumbra is a blood flow of 25 mL/100g of brain tissue/min. This level is dangerously low and can lead to loss of brain cells.  A blood flow of 8 mL/100g of brain tissue/min leads to an almost complete loss of functional neurons.  Consciousness is lost within 10 seconds of cessation of blood supply to the brain. Dr. Michael P. Gillespie 3
Color flow mapping has become an important clinical tool, for diagnosing a wide range of vascular diseases. Only the velocity component along the ultrasonic beam is estimated, so to find the actual blood velocity, the beam to flow angle has to be known. Because of the unpredictable nature of vascular hemodynamics, the flow angle cannot easily be found as the angle is temporally and spatially variant. Additionally the precision of traditional methods is severely lowered for high flow angles, and they breakdown for a purely transverse flow. To overcome these problems we propose a new method for estimating the transverse velocity component. The method measures the transverse velocity component by estimating the transit time of the blood between two parallel lines beamformed in receive. The method has been investigated using simulations performed with Field II. Using 15 emissions per estimate, a standard deviation of 1.64% and a bias of 1.13% are obtained for a beam to flow angle of 90 degrees. ...
For example, doctors usually determine whether the heart is pumping enough blood through the primary arteries to end organs by taking an ultrasound measurement called Velocity Time Integral (VTI). Hardware with AI-enabled features, such as Venue and Venue Go, developed by GE Healthcare, can get that VTI reading in seconds, not minutes. Thats because once physicians have an image of the patients beating heart, they can tap a button on the screen (Auto VTI) and the system will automatically place a box where the organs left ventricle meets the aorta, the bodys main artery. (The sample box looks similar to the frame that pops up over peoples faces when you take a photo on a smartphone.). Algorithms do the rest. Within seconds, they can analyze the outlined waveform showing the readings for the rate of blood flow in meters per second, and its volume in liters per minute. The technology dramatically reduces the number of keystrokes and the time it would take to calculate the flow rate manually. ...
How to Treat Shock. Shock is a life-threatening medical emergency caused by interruption of the normal blood flow, which cuts off the supply of oxygen and nutrients to cells and organs. Immediate emergency medical treatment is required....
Pitching velocity secrets from the pros. There are actually many of posts on the internet titled something similar to this article, most of them are useless, given that they focus primarily on upper body mechanics as the only methods to developing velocity. Any hard thrower will show you, there is a lot more to velocity…
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A student should be able to evaluate the speed of the object in the projectile and study the time of flight using range and horizontal velocity values ...
This apparatus allow the study of different methods of flow measurement in an incompressible fluid. This a direct application of the steady flow energy equation ; Bernoullis theorem.
Doppler Measurements & Calculations: MV E max vel: 83 cm/sec, MV A max vel: 86 cm/sec, MV E/A:0.96, MV dec time: 0.24 sec, Ao V2 max: 136cm/sec, Ao max PG: 7.0mmHg, LV max PG:3.0mmHg, LV V1 max:90 cm/sec, TR max vel: 204 cm/sec, TR max PG:17 mmHg,RVSPC(TR):22mmHg, RAP systole:5.0 ...
However, that all may be about to change. Blogger and macro specialist Naufal Sanaullah made an interesting observation recently: the United States economy looks like it is finally escaping its liquidity trap, thanks in large part to the stabilization in U.S. housing prices. Sanaullahs basic argument can be summed up in his thesis (emphasis added): Although deleveragings and liquidity traps are inextricably linked, sufficient income growth and credit velocity can allow for the economy to leave the liquidity trap, even as it continues to deleverage (through the denominators impact). This allows for a virtuous cycle to return, as traditional monetary policy regains efficacy and feeds into aggregate demand growth.. In other words, although the economy still has more to delever (reduce debt levels relative to GDP), the deleveraging process may now be helped along by monetary policy, instead of the two forces continuing to work in opposition to each other. To really understand what is going on ...