Blood Flow Studies Research Articles

Histogram analysis of laser speckle contrast image for cerebral blood flow monitoring

Laser speckle contrast imaging (LSCI) is a powerful tool for blood flow mapping. In this paper, we described a simple algorithm based on histogram analysis of laser speckle contrast image to provide rapid differentiation between macro- and microcirculations. The algorithm was successfully verified by the study of blood flow in rat cortex under functional activation.

A biomechanical approach to study the effect of body acceleration and slip velocity through stenotic artery

This paper presents the study of blood flow through stenosed artery with the effect of external body acceleration and slip velocity. Blood has been considered as non-Newtonian Bingham plastic fluid model. The non-linear differential equations governing the fluid flow are solved using the perturbation method and Matlab. The analytic expressions are derived for the velocity profile, flow rate, wall shear stress and effective viscosity. The computer codes are developed for the analysis of physiological parameters. The variation of flow variables with different parameters are shown graphically and discussed. It is noticed that the velocity and flow rate and resistance to flow increases but effective viscosity decreases due to wall slip. Body acceleration enhances the axial velocity and flow rate. However the wall shear stress decreases significantly with the application of slip velocity.

P1341 : Perform: An imaging study of arterial blood flow to liver metastases before and after selective internal radiotherapy

P1341 : Perform: An imaging study of arterial blood flow to liver metastases before and after selective internal radiotherapy

Ocular blood flow regulation in glaucoma - examination with the ocular pressure flow analyzer (OPFA)

The results of studies of ocular blood flow (BF) regulation of patients with primary open-angle glaucoma (POAG), normal-tension glaucoma (NTG) and ocular hypertension (OH) are presented. Examinations were carried out with the "OPFA", a newly developed ocular pressure flow analyzer (producer: tpm Lüneburg) on 92 patients with newly diagnosed glaucomas, among whom 48 patients had POAG, 22 NTG and 22 OH, and compared with age-matched groups of healthy subjects. The OPFA uses pneumatic coupling through special scleral suction cups to record ocular pulses with highly sensitive transducers and a suction pump for simultaneously increasing intraocular pressure (IOP). Following local drop anaesthesia on both eyes, IOP is artificially raised to suprasystolic values. While continuously lowering IOP, the ocular pulse is then recorded with increasing ocular perfusion pressure. We obtain the relative ocular pulse blood volume by correlating the ocular pulse amplitudes with a calibration volume of 1 µl. This enables us to collect reproducible data on intra- and inter-individual pulse blood volume (PVoc). The ocular perfusion pressure pulse blood volume curve characterizes the respective individual ocular circulation as well as systolic and diastolic ocular perfusion pressures. In healthy subjects, the ocular pulse blood volume remains stable over a certain range of ocular perfusion pressure (ppoc) changes. After exceeding a critical point (CP), the ocular pulse blood volume drops. We refer to the difference between the CP and IOP as the autoregulatory capacity (AC). In patients with POAG and in patients with NTG, the AC was reduced significantly compared with the groups of healthy subjects. The mean AC of patients with OH remained within the normal range. The ROC curves showed at an optimal cut-off value for POAG a sensitivity of 75.0 % and a specificity of 97.9 %, for NTG a sensitivity of 77.3 % and a specificity of 100 %. In patients with POAG and OH, the ocular arterial pressures were elevated. In patients with NTG they remained unchanged compared with the healthy subjects. The ocular perfusion pressures did not change in POAG as well as in NTG and OH. In patients with POAG and in patients with NTG the ocular BF regulation was impaired and detected by the OPFA device with a high level of reliability. Ocular arterial blood pressures were increased as a result of vascular regulation to keep up the ocular perfusion pressure and to maintain ocular perfusion.

Rescue Bypass for Revascularization After Ischemic Complications in the Treatment of Giant or Complex Intracranial Aneurysms

Surgical trapping or endovascular deconstruction commonly is used for the treatment of giant or complex intracranial aneurysms. Preoperative balloon test occlusion and cerebral blood flow studies and intraoperative neurophysiologic monitoring can indicate whether sufficient collateralization exists or whether revascularization is needed. Hemodynamic insufficiency can occur, however, despite passing these tests, necessitating posttreatment revascularization. We conducted a retrospective review of patients who underwent surgical or endovascular parent vessel occlusion for the management of giant or complex intracranial aneurysms and subsequently required rescue bypass for symptoms of hemodynamic insufficiency. Pre- and postrevascularization functional status was measured with the modified Rankin Scale. During a 15-year period from 1997 to 2012, a rescue bypass was performed in 5 patients each harboring a giant or complex intracranial internal carotid artery (ICA) aneurysm that was treated with surgical trapping or endovascular deconstruction in a previous procedure. All bypasses were extracranial-to-intracranial and included cervical ICA to middle cerebral artery, subclavian to middle cerebral artery, and cervical ICA to supraclinoid ICA anastomoses via either a saphenous vein or radial artery graft. Functional outcome at time of last follow-up was improved in each patient (improvement in modified Rankin Scale of 1-3 points). Ischemic complications must always be anticipated in the treatment of giant or complex intracranial aneurysms, even if pre- and intraoperative blood flow studies indicate sufficient collateralization. Here we show that extracranial-to-intracranial bypass is an effective option to rescue unanticipated hemodynamic insufficiency after parent vessel occlusion. This study emphasizes the need for cerebrovascular surgeons to maintain proficiency in complex bypass techniques.

Development of radioiodinated lipophilic cationic compounds for myocardial imaging

IntroductionTc-99m compounds are mainly used in myocardial blood flow studies. These compounds, however, are produced by a generator and alternate single photon emission computed tomography (SPECT) radiopharmaceuticals are therefore required to avoid the risks posed by generator failure. Three radiolabeled compounds, including [125I]p-iodobenzyl triphenylphosphonium ([125I]ITPP), [125I]p-Iodobenzyl dipropylphenylphosphonium ([125I]IDPP) and [125I]p-iodobenzyl methyldiphenylphosphonium ([125I]IMPP), have been synthesized in the current study. All three of these compounds contain a lipophilic cation, which enhances their cell permeability properties and allows them to accumulate in the myocardium as SPECT probes. Methods4-(2-Tributylstannyl) benzyl alcohol was mixed with [125I]NaI in the presence of aqueous hydrogen peroxide and hydrochloric acid to allow for the synthesis of 4-[125I]iodobenzyl alcohol. Bromination of the alcohol under standard conditions gave 4-[125I]iodo benzyl bromide, which was treated with triphenylphosphine, dipropylphenylphosphine or methyldiphenylphosphine to give [125I]ITPP, [125I]IDPP and [125I]IMPP, respectively. These compounds were evaluated in biodistribution and SPECT studies in normal ddY mice. ResultsAll three of the radiolabeled compounds were synthesized in approximately 60% yield with radiochemical purities greater than 99%. The specific activity of each compound was 74 GBq/μmol. The results of the biodistribution and SPECT studies showed that all compounds accumulated preferentially in the heart in vivo, especially [125I]IDPP. Conclusion[123I] IDPP could be used in clinical practice as a novel myocardial imaging agent.

Study of blood flow in one half of cosine shaped stenosis in the presence of magnetic field

In the 21st century, the flow of blood through stenosed arteries is one of the main research areas in computational biomechanics due to its role in the medical field. In the present investigation, a study of non-Newtonian blood flow in one half of cosine shaped stenosed artery in the presence of externally applied transverse magnetic field is proposed. The expressions for dimensionless axial velocity, wall shear stress and volumetric flow rate have been obtained. The effect of externally applied magnetic field on blood flow has been discussed with the help of graphs. All the flow characteristics are found to be affected in the presence of externally applied transverse magnetic field.

Numerical Study of Turbulent Pulsatile Blood Flow through Stenosed Artery Using Fluid-Solid Interaction.

The turbulent pulsatile blood flow through stenosed arteries considering the elastic property of the wall is investigated numerically. During the numerical model validation both standard k-ε model and RNG K-ε model are used. Compared with the RNG K-ε model, the standard K-ε model shows better agreement with previous experimental results and is better able to show the reverse flow region. Also, compared with experimental data, the results show that, up to 70% stenosis, the flow is laminar and for 80% stenosis the flow becomes turbulent. Assuming laminar or turbulent flow and also rigid or elastic walls, the results are compared with each other. The investigation of time-averaged shear stress and the oscillatory shear index for 80% stenosis show that assuming laminar flow will cause more error than assuming a rigid wall. The results also show that, in turbulent flow compared with laminar flow, the importance of assuming a flexible artery wall is more than assuming a rigid artery wall.

Experimental study of hemodynamics in the Circle of Willis.

BackgroundThe Circle of Willis (CoW) is an important collateral pathway of the cerebral blood flow. An experimental study of the cerebral blood flow (CBF) distribution in different anatomical variations may help to a better understanding of the collateral mechanism of the CoW.MethodsAn in-vitro test rig was developed to simulate the physiological cerebral blood flow in the CoW. Ten anatomical variations were considered in this study, include a set of different degrees of stenosis in L-ICA and L-ICA occlusion coexist with common anatomical variations. Volume flow rates of efferent arteries and pressure signals at the end of communicating arteries of each case were recorded. Physiological pressure waveforms were applied as inlet boundary condition.ResultsIn the development of L-ICA stenosis, the total CBF decreases with the increase of stenosis degree. The blood supply of ipsilateral middle cerebral artery (MCA) was affected most by the stenosis of L-ICA. Anterior communicating artery (ACoA) and ipsilateral posterior communicating artery (PCoA) function as important collateral pathways of cerebral collateral circulation when unilateral stenosis occurred. The blood supply of anterior cerebral circulation was compensated by the posterior cerebral circulation through ipsilateral PCoA when L-ICA stenosis degree is greater than 40% and the affected side was compensated immediately by the unaffected side through ACoA. Blood flow of the anterior circulation and the total CBF reached the minimum among all cases studied when L-ICA occlusion coexist with the absence of PCoA.ConclusionThe results demonstrated the flow distribution patterns of the CoW under anatomical variations and clarified the collateral mechanism of the CoW. The flow ACoA is the most sensitive indexes to the morphology change of ipsilateral ICA. The relative independence of the circulation in anterior and posterior sections of the CoW is not broken and the function of ipsilateral PCoA is not activated until a severe stenosis of unilateral ICA occurs. PCoA is the most important collateral pathway of the collateral circulation and the missing of PCoA has the highest risk of stroke when the ipsilateral ICA has severe stenosis. These findings may provide the basis for future therapeutic and diagnosis applications.

Quantification of myocardial blood flow with cardiovascular magnetic resonance throughout the cardiac cycle.

BackgroundMyocardial blood flow (MBF) varies throughout the cardiac cycle in response to phasic changes in myocardial tension. The aim of this study was to determine if quantitative myocardial perfusion imaging with cardiovascular magnetic resonance (CMR) can accurately track physiological variations in MBF throughout the cardiac cycle.Methods30 healthy volunteers underwent a single stress/rest perfusion CMR study with data acquisition at 5 different time points in the cardiac cycle (early-systole, mid-systole, end-systole, early-diastole and end-diastole). MBF was estimated on a per-subject basis by Fermi-constrained deconvolution. Interval variations in MBF between successive time points were expressed as percentage change. Maximal cyclic variation (MCV) was calculated as the percentage difference between maximum and minimum MBF values in a cardiac cycle.ResultsAt stress, there was significant variation in MBF across the cardiac cycle with successive reductions in MBF from end-diastole to early-, mid- and end-systole, and an increase from early- to end-diastole (end-diastole: 4.50 ± 0.91 vs. early-systole: 4.03 ± 0.76 vs. mid-systole: 3.68 ± 0.67 vs. end-systole 3.31 ± 0.70 vs. early-diastole: 4.11 ± 0.83 ml/g/min; all p values <0.0001). In all cases, the maximum and minimum stress MBF values occurred at end-diastole and end-systole respectively (mean MCV = 26 ± 5%). There was a strong negative correlation between MCV and peak heart rate at stress (r = −0.88, p < 0.001). The largest interval variation in stress MBF occurred between end-systole and early-diastole (24 ± 9% increase). At rest, there was no significant cyclic variation in MBF (end-diastole: 1.24 ± 0.19 vs. early-systole: 1.28 ± 0.17 vs.mid-systole: 1.28 ± 0.17 vs. end-systole: 1.27 ± 0.19 vs. early-diastole: 1.29 ± 0.19 ml/g/min; p = 0.71).ConclusionQuantitative perfusion CMR can be used to non-invasively assess cyclic variations in MBF throughout the cardiac cycle. In this study, estimates of stress MBF followed the expected physiological trend, peaking at end-diastole and falling steadily through to end-systole. This technique may be useful in future pathophysiological studies of coronary blood flow and microvascular function.

Stochastic dynamics in a fluid--plate interaction model with the only longitudinal deformations of the plate

We consider a stochastically perturbed coupled system consisting of linearized 3D Navier--Stokes equations in a bounded domain and the classical (nonlinear) elastic plate equation for in-plane motions on a flexible flat part of the boundary. This kind of models arises in the study of blood flows in large arteries. Our main result states the existence of a random pullback attractor of finite fractal dimension. Our argument is based on some modification of the method of quasi-stability estimates recently developed for deterministic systems.

Comparative study of vertebral arterial blood flow between arteriosclerosis patients and healthy people

Objective To conduct comparative study of vertebral artery blood flow of arteriosclerosis patients and healthy people using color Doppler ultrasound (CDUS),and to discuss the effect of arteriosclerosis on vertebral arterial blood flow.Methods Two hundred and eighty-five cases of vertebral artery test were collected and divided in to normal group of one hundred and thirty-five cases and vertebral artery sclerosis group of one hundred and fifty cases according to the presence of vertebral artery sclerosis.Time averaged maximum velocity (TAMV) and vertebral artery diameter(D) of vertebral artery were measured using CDUS technique.Unilateral vertebral artery blood flow and total blood flow were calculated.Results The vertebral artery TAMV and total blood flow of arteriosclerosis group was both lower than that of normal group (P＜0.05).Left side vertebral artery diameters of the two groups were higher than that of the right side.Conclusions Arteriosclerosis can reduce vertebral artery TAMV and blood flow.The inner diameter of the left side vertebral artery dominates the artery blood flow. Key words: Color Doppler ultrasound; Vertebral artery; Blood flow; Arteriosclerosis

Comparative study of healthy vertebral artery blood flow from plain and plateau region

Objective To conduct comparative study of healthy vertebral artery (VA) blood flow of subjects from plain and plateau region using color Doppler ultrasound (CDUS) measurement,and to investigate the influence of plateau on blood flow of VA.Methods One hundred and thirty-five subjects from plain region and eighty from high altitude region were recruited.Time averaged maximum velocity and inradium (D) of VA were measured with CDUS technology.Unilateral VA blood flow and total blood flow were calculated.Peripheral blood viscosity measurement was carried out by testing low cut,mid cut,high cut,plasma viscosity and red blood cell count (RBC),hemoglobin concentration (HGB),hematocrit (HCT).Results VA diameter,blood viscosity,RBC,HGB,and HCT of plateau group are all higher than that of the plain group (P＜0.05),while the total blood flow was lower than that of plain group and the value of male was higher than that of female (P＜0.05).The inradiums of right side VA were larger than that of the left side (P＜0.05) in plain group,while no difference was observed in plateau group (P＞0.05).Conclusions Long term (＞10 years) living in plateau hypoxia (altitude＞3 000 m) environment can reduce the average flow velocity and the blood flow of VA. Key words: Color Doppler ultrasound; Plain; Plateau; Vertebral artery; Blood flow

New Approaches to Treatment of Severe Intrauterine Growth Restriction.

IntroductionIntrauterine growth restriction (IUGR) is a leading cause of perinatal morbidity and mortality due to placental insufficiency. Currently, one of the new approaches to treating this disease is the injection of nutrients to the fetus through intravascular port-systems (catheters).ObjectiveTo assess the impact of nutrient injections as treatment to fetuses with severe growth retardation.Materials and methodsPregnant women with IUGR (abdominal circumference (AC) < 5th percentile) with the absence of diastolic flow in the umbilical artery and a fetal gestational age of less than 30 weeks were randomly divided into two groups. The treatment group included six pregnant women who had an intravascular port-system for the infusion of nutrients (amino acids and glucose) in the umbilical vein of the fetus for 14 ± 3 days. The control group consisted of eight patients who received only traditional dynamic monitoring and delivery at the optimum time of pregnancy. Fetal status was assessed using ultrasound equipment Accuvix V20 (Medison, South Korea) by examining indicators of biometry and Doppler study of blood flow in utero, umbilical arteries, middle cerebral artery, and ductus venosus with fetal vascular resistance index calculation - pulsatility index (PI). Criteria for blood flow disturbances in the vessels were considered PI values above normal values for their gestational age, which were defined as absence or reverse blood flow in a diastole in the umbilical artery.ResultsIn a comparative analysis of the two groups, the treatment led to a 44.7% increase in AC of the fetus (121.0 ± 11.5 mm and 219.3 ± 18.3 mm, respectively, p < 0.001). In all cases, the profile of blood flow in the umbilical artery had a positive diastolic component. As a result, there was a 45.3% decrease in PI in the umbilical artery (2.14 ± 0.54 and 1.17 ± 0.15, respectively, p < 0.05). Average fetal weight in the study group was not significantly higher than the control group (1,120.3 ± 213.6 g and 909.6 ± 131.4 g, p > 0.05).ConclusionThus, injection of nutrients to the fetuses through intravascular port-system improved placental perfusion and metabolism, which has the potential for improved fetal growth. This, in turn, promoted full-term pregnancy and improved perinatal outcomes in fetal pathology.

Potential application of ivim and dwi imaging in parkinson's disease

Parkinson’s disease (PD) is a progressive degenerative neurological condition, which origin remains unclear. We are interested in proposing the study of blood flow in the substantia nigra (SN) in PD patients, based on findings that demonstrated relative hypoactivity in PD patients located to subthalamic nucleus and SN. It is believed that this hipoactivity may suggest changes in the blood flow to the SN, where the particular loss of dopaminergic neurons occurs. The method used is the Incoherent Motion Intravoxel (IVIM) that allows measurement of blood flow to the microvascular level and recently has been producing high resolution quantitative perfusion maps. This paper proposes to measure the perfusion in PD patients and find any correlation with neural activity and water displacements within the tissue. Assuming decreasing the local perfusion suggests the possible impairments that affect the neural activity in PD causing the progressive death of neurons in the SN.

Hemodynamics in the microcirculation and in microfluidics.

Hemodynamics in microcirculation is important for hemorheology and several types of circulatory disease. Although hemodynamics research has a long history, the field continues to expand due to recent advancements in numerical and experimental techniques at the micro-and nano-scales. In this paper, we review recent computational and experimental studies of blood flow in microcirculation and microfluidics. We first focus on the computational studies of red blood cell (RBC) dynamics, from the single cellular level to mesoscopic multiple cellular flows, followed by a review of recent computational adhesion models for white blood cells, platelets, and malaria-infected RBCs, in which the cell adhesion to the vascular wall is essential for cellular function. Recent developments in optical microscopy have enabled the observation of flowing blood cells in microfluidics. Experimental particle image velocimetry and particle tracking velocimetry techniques are described in this article. Advancements in micro total analysis system technologies have facilitated flowing cell separation with microfluidic devices, which can be used for biomedical applications, such as a diagnostic tool for breast cancer or large intestinal tumors. In this paper, cell-separation techniques are reviewed for microfluidic devices, emphasizing recent advances and the potential of this fast-evolving research field in the near future.

Сколиоз и аномалии краниовертебрального перехода: взаимосвязь или сочетание?

The paper presents the point of view of the anomaly Chiari 1 and retroareolar cyst from the position of the possible causal correlation of these diseases with scoliosis. Scoliosis occurs in patients with anomaly Chiari 1 according to different data from 35 to 60%. The authors didn’t find scientific information about the combination of retroareolar cysts with scoliosis. The authors made an attempt to combine these diseases from the point of view of a single etiopathogenetic mechanisms based on the study of blood flow at the level craniovertebral transition. Patients were divided into two groups and two subgroups. The first group included 67 patients with anomaly Chiari 1, the second – 26 patients with retroareolar cysts. Subgroups were formed from patients, necessarily had scoliosis: the subgroup «A» is for patients with scoliosis and anomaly Chiari 1, the subgroup “B” – for patients with scoliosis and retroareolar cyst. Neurological, x-ray examination was carried out in all patients. The diagnostic and treatment algorithm for patients with a combination of scoliosis and anomaly Chiari 1 taking into account the dominant pathology has been defined. It is established that scoliosis often combined with abnormalities of craniovertebral transition, including retroareolar cyst. Neurosurgical treatment of anomalies of craniovertebral transition can posi-tively influence on the course of the accompanying scoliosis.

Blood flow study of Williamson fluid through stenosed arteries with permeable walls

The present work deals with the theoretical study of the unsteady blood flow of a Williamson fluid through composite stenosed arteries with permeable walls. The highly non-linear momentum equations of the Williamson fluid model are simplified by considering the mild stenosis case and the perturbation solutions are evaluated. The expressions for velocity, flow impedance, wall shear stress and shearing stress at the stenosis throat are computed and discussed through graphs for different physical parameters of interest.

Сlinical and neurophysiological estimation of cognitive function in patients with chronic cerebral ischemia in a period of recovery after surgery

Objective – to estimate the peculiarities of the cognitive function disorders and cognitive evoked potentials (CEP) changes in patients with cerebrovascular deseasis (CVD) in post-operative period and period of recovery.Methods and subjects. 42 patients with chronic cerebral circulation impairment were examined. The patients were operated about the hemodynamic significantly stenosys in internal carotid or/and vertebral artery. The first clinical group included 20 patients, who had acute ischemic stroke; the second group comprised 22 patients without data on ischemic stroke in anamnesis. The methods used: clinical, neurological; neuropsychological testing (NPT), MRI, ultrasound study of the cerebral blood flow, EEG mapping, CEP P300.Results. All studies were conducted in the period of recovery 6 months – 2 years after operation: carotid endarterectomy (14), endovascular angioplasty with stenting (12). Positive changes in blood flow in the area of stenosis, and in the affected intracranial artery and its branches were observed after surgical removal of stenosis. As evidence of cognitive impairment using the results of the NPT decrease by 1.5 σ or more, as a sign of slowing of mental processes – significant increase of the latent period of P300 to 2 σ or more, a significant reduction in the amplitude and increase asymmetry of these indicators. It confirms the correlation of negative effect on the NPT-CEP indicators and next factors: elderly age, decreased blood flow in the proximal segments of the middle cerebral artery by more than 20% of the age norms, absence (significant decrease) in reserve capacity of cerebral blood flow, site of the lesion in the right hemisphere, the presence of seizures.Conclusions. Complex methodology of NTP-CEP allows to educe violations of cognitive functions for patients with CVD in the dynamics of surgery treatment and to control renewal.

Radial-basis-function level-set-based regularized Gauss–Newton-filter reconstruction scheme for dynamic shape tomography

The dynamic reconstruction problem in tomographic imaging is encountered in several applications, such as species determination, the study of blood flow through arteries/veins, motion compensation in medical imaging, and process tomography. The reconstruction method of choice is the Kalman filter and its variants, which, however, are faced by issues of filter tuning. In addition, since the time-propagation models of physical parameters are typically very complex, most of the time, a random walk model is considered. For geometric deformations, affine models are typically used. In our work, with the objectives of minimizing tuning issues and reconstructing time-varying geometrically deforming features of interest with affine in addition to pointwise-normal scaling motions, a novel level-set-based reconstruction scheme for ray tomography is proposed for shape and electromagnetic parameters using a regularized Gauss-Newton-filter-based scheme. We use an implicit Hermite-interpolation-based radial basis function representation of the zero level set corresponding to the boundary curve. Another important contribution of the paper is an evaluation of the shape-related Frechet derivatives that does not need to evaluate the pointwise Jacobian (the ray-path matrix in our ray-tomography problem). Numerical results validating the formulation are presented for a straight ray-based tomographic reconstruction. To the best of our knowledge, this paper presents the first tomographic reconstruction results in these settings.