Pulsatile Research Articles

Biomechanical Assessment of Red Blood Cells in Pulsatile Blood Flows

As rheological properties are substantially influenced by red blood cells (RBCs) and plasma, the separation of their individual contributions in blood is essential. The estimation of multiple rheological factors is a critical issue for effective early detection of diseases. In this study, three rheological properties (i.e., viscoelasticity, RBC aggregation, and blood junction pressure) are measured by analyzing the blood velocity and image intensity in a microfluidic device. Using a single syringe pump, the blood flow rate sets to a pulsatile flow pattern (Qb[t] = 1 + 0.5 sin(2πt/240) mL/h). Based on the discrete fluidic circuit model, the analytical formula of the time constant (λb) as viscoelasticity is derived and obtained at specific time intervals by analyzing the pulsatile blood velocity. To obtain RBC aggregation by reducing blood velocity substantially, an air compliance unit (ACU) is used to connect polyethylene tubing (i.d. = 250 µm, length = 150 mm) to the blood channel in parallel. The RBC aggregation index (AI) is obtained by analyzing the microscopic image intensity. The blood junction pressure (β) is obtained by integrating the blood velocity within the ACU. As a demonstration, the present method is then applied to detect either RBC-aggregated blood with different concentrations of dextran solution or hardened blood with thermally shocked RBCs. Thus, it can be concluded that the present method has the ability to consistently detect differences in diluent or RBCs in terms of three rheological properties.

Impaired damping of cerebral blood flow velocity pulsatility is associated with the number of perivascular spaces as measured with 7T MRI

Arterial walls stiffen with age, cardiovascular risk factors, and various vascular diseases, which may lead to less damping of the arterial blood flow pulse, subsequent microvascular damage, and enlarged perivascular spaces (PVS). However, the exact interplay between these processes is unclear. This study aimed to investigate the relation between blood flow velocity pulsatility in the small lenticulostriate arteries and their supplying middle cerebral artery and the respective damping factor (DF), with the number of MRI-visible PVS in elderly subjects. Blood flow velocity waveforms were obtained in 45 subjects (median age [range]: 64 [48–81] years, 47% male) using 7T MRI. PVS were scored in the basal ganglia (BG) and centrum semiovale (CSO). Spearman correlation analyses were used to determine associations of the blood flow pulsatility and the DF, with PVS score, adjusted for age and sex. We found a significant association between a lower DF and a higher number of PVS in the BG (rs = −0.352, P = 0.021), but not in the CSO. This finding supports the supposed pathophysiological mechanism in which excessive kinetic energy deposition leads to damage of small perforating arteries and contributes to the enlargement of PVS at the level of the BG, but possible other pathways might also be of influence.

MRV challenge 2: phase locked turbulent measurements in a roughness array

Magnetic resonance velocimetry (MRV) provides capabilities to measure three velocity components across three-dimensional fields of view without the need for optical accessibility. Predominant usage of the technique in engineering applications centers on steady flows and the discussion of a single time-averaged set of data. In this second MRV Challenge comparison, phase-locked MRV measurements of a pulsatile flow are conducted by five teams from across the globe. A geometry is explored which consists of turbulent flow past six identical cubic elements placed in the center of a square water channel, with partial elements along each side of periodically varying heights. A pulsatile injection flow through the floor between the second and third cubic roughness elements creates a three-dimensional jet that interacts with the complex cube wakes. The details of each scan sequence are summarized for the teams. Results are compared for three different time windows—one pre-injection, a second while the injection flow accelerates, and a third during a quasi-steady condition with the injector fully on. Finally, the influence of the temporal resolution selection for the phase locked MRV is discussed. The results are remarkably similar despite the complex flow configuration selection and showcase a relatively underutilized capability to obtain time-dependent, volumetric data for periodic flows through three-dimensional geometries using MRI. Recommendations for best practices are also provided.

Characterising spinal cerebrospinal fluid flow in the pig with phase-contrast magnetic resonance imaging

BackgroundDetecting changes in pulsatile cerebrospinal fluid (CSF) flow may assist clinical management decisions, but spinal CSF flow is relatively understudied. Traumatic spinal cord injuries (SCI) often cause spinal cord swelling and subarachnoid space (SAS) obstruction, potentially causing pulsatile CSF flow changes. Pigs are emerging as a favoured large animal SCI model; therefore, the aim of this study was to characterise CSF flow along the healthy pig spine.MethodsPhase-contrast magnetic resonance images (PC-MRI), retrospectively cardiac gated, were acquired for fourteen laterally recumbent, anaesthetised and ventilated, female domestic pigs (22–29 kg). Axial images were obtained at C2/C3, T8/T9, T11/T12 and L1/L2. Dorsal and ventral SAS regions of interest (ROI) were manually segmented. CSF flow and velocity were determined throughout a cardiac cycle. Linear mixed-effects models, with post-hoc comparisons, were used to identify differences in peak systolic/diastolic flow, and maximum velocity (cranial/caudal), across spinal levels and dorsal/ventral SAS. Velocity wave speed from C2/C3 to L1/L2 was calculated.ResultsPC-MRI data were obtained for 11/14 animals. Pulsatile CSF flow was observed at all spinal levels. Peak systolic flow was greater at C2/C3 (dorsal: − 0.32 ± 0.14 mL/s, ventral: − 0.15 ± 0.13 mL/s) than T8/T9 dorsally (− 0.04 ± 0.03 mL/s; p < 0.001), but not different ventrally (− 0.08 ± 0.08 mL/s; p = 0.275), and no difference between thoracolumbar levels (p > 0.05). Peak diastolic flow was greater at C2/C3 (0.29 ± 0.08 mL/s) compared to T8/T9 (0.03 ± 0.03 mL/s, p < 0.001) dorsally, but not different ventrally (p = 1.000). Cranial and caudal maximum velocity at C2/C3 were greater than thoracolumbar levels dorsally (p < 0.001), and T8/T9 and L1/L2 ventrally (p = 0.022). Diastolic velocity wave speed was 1.41 ± 0.39 m/s dorsally and 1.22 ± 0.21 m/s ventrally, and systolic velocity wave speed was 1.02 ± 0.25 m/s dorsally and 0.91 ± 0.22 m/s ventrally.ConclusionsIn anaesthetised and ventilated domestic pigs, spinal CSF has lower pulsatile flow and slower velocity wave propagation, compared to humans. This study provides baseline CSF flow at spinal levels relevant for future SCI research in this animal model.

Efficacy of ultrasound vector flow imaging in tracking omnidirectional pulsatile flow.

Ultrasound vector flow imaging (VFI) shows potential as an emerging non-invasive modality for time-resolved flow mapping. However, its efficacy in tracking multidirectional pulsatile flow with temporal resolvability has not yet been systematically evaluated because of the lack of an appropriate test protocol. We present the first systematic performance investigation of VFI in tracking pulsatile flow in a meticulously designed scenario with time-varying, omnidirectional flow fields (with flow angles from 0° to 360°). Ultrasound VFI was performed on a three-loop spiral flow phantom (4mm diameter; 5mm pitch) that was configured to operate under pulsatile flow conditions (10ml/s peak flow rate; 1Hz pulse rate; carotid pulse shape). The spiral lumen geometry was designed to simulate recirculatory flow dynamics observed in the heart and in curvy blood vessel segments such as the carotid bulb. The imaging sequence was based on steered plane wave pulsing (-10°, 0°, +10° steering angles; 5MHz imaging frequency; 3.3kHz interleaved pulse repetition frequency). VFI's pulsatile flow estimation performance and its ability to detect secondary flow were comparatively assessed against flow fields derived from computational fluid dynamics (CFD) simulations that included consideration of fluid-structure interactions (FSI). The mean percentage error (MPE) and the coefficient of determination (R2 ) were computed to assess the correspondence of the velocity estimates derived from VFI and CFD-FSI simulations. In addition, VFI's efficacy in tracking pulse waves was analyzed with respect to pressure transducer measurements made at the phantom's inlet and outlet. Pulsatile flow patterns rendered by VFI agreed with the flow profiles computed from CFD-FSI simulations (average MPE: -5.3%). The shape of the VFI-measured velocity magnitude profile generally matched the inlet flow profile. High correlation exists between VFI measurements and simulated flow vectors (lateral velocity: R2 =0.8; axial velocity R2 =0.89; beam-flow angle: R2 =0.98; p<0.0001 for all three quantities). VFI was found to be capable of consistently tracking secondary flow. It also yielded pulse wave velocity (PWV) estimates (5.72±1.02m/s) that, on average, are within 6.4% of those obtained from pressure transducer measurements (6.11±1.15m/s). VFI can consistently track omnidirectional pulsatile flow on a time-resolved basis. This systematic investigation serves well as a quality assurance test of VFI.

Visualization of multiphase pulsatile blood over single phase blood flow in a patient specific stenosed left coronary artery using image processing technique.

Coronary arteries disease has been reported as one of the principal roots of deaths worldwide. The aim of this study is to analyze the multiphase pulsatile blood flow in the left coronary artery tree with stenosis. The 3D left coronary artery model was reconstructed using 2D computerized tomography (CT) scan images. The Red Blood Cell (RBC) and varying hemodynamic parameters for single and multiphase blood flow conditions were analyzed. Results asserted that the multiphase blood flow modeling has a maximum velocity of 1.017 m/s and1.339 m/s at the stenosed region during the systolic and diastolic phases respectively. The increase in Wall Shear Stress (WSS) observed at the stenosed region during the diastole phase as compared during the systolic phase. It was also observed that the highest Oscillatory Shear Index (OSI) regions are found in the downstream area of stenosis and across the bifurcations. The increase in RBCs velocity from 0.45 m/s to 0.6 m/s across the stenosis was also noticed. The computational multiphase blood flow analysis improves the understanding and accuracy of the complex flow conditions of blood elements (RBC and Plasma) and provides the progression of the disease development in the coronary arteries. This study helps to enhance the diagnosis of the blocked (stenosed) arteries more precisely compared to the single-phase blood flow modeling.

Influence of blood viscosity models and boundary conditions on the computation of hemodynamic parameters in cerebral aneurysms using computational fluid dynamics.

Computational fluid dynamics (CFD) is widely used to calculate hemodynamic parameters that are known to influence cerebral aneurysms. However, the boundary conditions for CFD are chosen without any specific criteria. Our objective is to establish the recommendations for setting the analysis conditions for CFD analysis of the cerebral aneurysm. The plug and the Womersley flow were the inlet boundary conditions, and zero and pulsatile pressures were the outlet boundary conditions. In addition, the difference in the assumption of viscosity was analyzed with respect to the flow rate. The CFD process used in our research was validated using particle image velocimetry experiment data from Tupin et al.'s work to ensure the accuracy of the simulations. It was confirmed that if the entrance length was sufficiently secured, the inlet and outlet boundary conditions did not affect the CFD results. In addition, it was observed that the difference in the hemodynamic parameter between Newtonian and non-Newtonian fluid decreased as the flow rate increased. Furthermore, it was confirmed that similar tendencies were evaluated when these recommendations were utilized in the patient-specific cerebral aneurysm models. These results may help conduct standardized CFD analyses regardless of the research group.

Channel impeller design for centrifugal blood pump in hybrid pediatric total artificial heart: Modeling, magnet integration, and hydraulic experiments.

The purpose of this research is to address ongoing device shortfalls for pediatric patients by developing a novel pediatric hybrid total artificial heart (TAH). The valveless magnetically-levitated MCS device (Dragon Heart) has only two moving parts, integrates an axial and centrifugal blood pump into a single device, and will occupy a compact footprint within the chest for the pediatric patient population. Prior work on the Dragon Heart focused on the development of pump designs to achieve hemodynamic requirements. The impeller of these pumps was shaft-driven and thus could not be integrated for testing. The presented research leverages an existing magnetically levitated axial flow pump and focuses on centrifugal pump development. Using the axial pump diameter as a geometric constraint, a shaftless, magnetically supported centrifugal pump was designed for placement circumferentially around the axial pump domain. The new design process included the computational analysis of more than 50 potential centrifugal impeller geometries. The resulting centrifugal pump designs were prototyped and tested for levitation and no-load rotation, followed by in vitro testing using a blood analog. To meet physiologic demands, target performance goals were pressure rises exceeding 90 mm Hg for flow rates of 1-5L/min with operating speeds of less than 5000 RPM. Three puck-shaped, channel impellers for the centrifugal blood pump were selected based on achieving performance and space requirements for magnetic integration. A quasi-steady flow analysis revealed that the impeller rotational position led to a pulsatile component in the pressure generation. After prototyping, the centrifugal prototypes (3, 4, and 5 channeled designs) demonstrated levitation and no-load rotation. Hydraulic experiments established pressure generation capabilities beyond target requirements. The pressure-flow performance of the prototypes followed expected trends with a dependence on rotational speed. Pulsatile blood flow was observed without pump-speed modulation due to rotating channel passage frequency. The results are promising in the advancement of this pediatric TAH. The channeled impeller design creates pressure-flow curves that are decoupled from the flow rate, a benefit that could reduce the required controller inputs and improve treatment of hypertensive patients.

Deep learning-based hemodynamic prediction of carotid artery stenosis before and after surgical treatments.

Hemodynamic prediction of carotid artery stenosis (CAS) is of great clinical significance in the diagnosis, prevention, and treatment prognosis of ischemic strokes. While computational fluid dynamics (CFD) is recognized as a useful tool, it shows a crucial issue that the high computational costs are usually required for real-time simulations of complex blood flows. Given the powerful feature-extraction capabilities, the deep learning (DL) methodology has a high potential to implement the mapping of anatomic geometries and CFD-driven flow fields, which enables accomplishing fast and accurate hemodynamic prediction for clinical applications. Based on a brain/neck CT angiography database of 280 subjects, image based three-dimensional CFD models of CAS were constructed through blood vessel extraction, computational domain meshing and setting of the pulsatile flow boundary conditions; a series of CFD simulations were undertaken. A DL strategy was proposed and accomplished in terms of point cloud datasets and a DL network with dual sampling-analysis channels. This enables multimode mapping to construct the image-based geometries of CAS while predicting CFD-based hemodynamics based on training and testing datasets. The CFD simulation was validated with the mass flow rates at two outlets reasonably agreed with the published results. Comprehensive analysis and error evaluation revealed that the DL strategy enables uncovering the association between transient blood flow characteristics and artery cavity geometric information before and after surgical treatments of CAS. Compared with other methods, our DL-based model trained with more clinical data can reduce the computational cost by 7,200 times, while still demonstrating good accuracy (error<12.5%) and flow visualization in predicting the two hemodynamic parameters. In addition, the DL-based predictions were in good agreement with CFD simulations in terms of mean velocity in the stenotic region for both the preoperative and postoperative datasets. This study points to the capability and significance of the DL-based fast and accurate hemodynamic prediction of preoperative and postoperative CAS. For accomplishing real-time monitoring of surgical treatments, further improvements in the prediction accuracy and flexibility may be conducted by utilizing larger datasets with specific real surgical events such as stent intervention, adopting personalized boundary conditions, and optimizing the DL network.

Wall Shear Stress Measurement in Carotid Artery Phantoms with Variation in Degree of Stenosis Using Plane Wave Vector Doppler

Wall shear stress (WSS) plays an important role in the formation, growth, and rupture of atherosclerotic plaques in arteries. This study measured WSS in diseased carotid artery phantoms with degrees of stenosis varying from 0 to 60% with both steady and pulsatile flow. Experiments were performed using in silico and real flow phantoms. Blood velocities were estimated using plane wave (PW) vector Doppler. Wall shear stress was then estimated from the velocity gradient near the wall multiplied by the viscosity of a blood-mimicking fluid. The estimated WSS using the in silico phantom agreed within 10% of the ground-truth values (root-mean-square error). The phantom experiment showed that the mean WSS and maximum WSS increased with the increasing degree of stenosis. The simulation and experiment results provide the necessary validation data to give confidence in WSS measurements in patients using the PW vector Doppler technique.

Biocompatibility of the Oxygenator on Pulsatile Flow by Electron Microscope.

Extracorporeal perfusion flow type requires further investigation. The aim of this study is to compare the effects of pulsatile and nonpulsatile flow on oxygenator fibers that were analyzed by scanning electron microscope (SEM) and to extensively study patients' coagulation profiles, inflammatory markers, and functional blood tests. Twelve patients who had open heart surgery were randomly divided into two groups; the nonpulsatile flow (group NP, six patients) and pulsatile flow (group P, six patients) groups. Both superficial view and axial sections of the oxygenator fiber samples were examined under SEM to compare the thickness of absorbed blood proteins and amount of blood cells on the surface of oxygenators. Platelet count, coagulation profile, and inflammatory predictors were also studied from the blood samples. Fibrinogen levels after cardiopulmonary bypass were significantly lower in group NP (group P, 2.57±2.78 g/L; group NP; 2.39±0.70 g/L, P=0.03). Inflammatory biomarkers such as C-reactive protein, interleukin (IL)-6, IL-12, apelin, S100β, and tumor necrosis factor alpha were comparable in both groups. Axial sections of the oxygenator fiber samples had a mean thickness of 45.2 µm and 46.5 µm in groups P and NP, respectively, and this difference is statistically significant (P=0.006). Superficial view of the fiber samples showed obviously lower platelet, leukocyte, and erythrocyte levels in group P. Our study demonstrated that both cellular elements and protein adsorption on oxygenator fibers are lower in the group P than in the group NP. Pulsatile perfusion has better biocompatibility on extracorporeal circulation when analyzed by SEM technique.

Dispersion of Heterogeneous Medium in Pulsatile Blood Flow and Absolute Pulsatile Flow Velocity Quantification.

Heterogeneous medium enhanced angiogr- ams are key diagnostic tools in clinical practice; the associated hemodynamic information is crucial for diagnosing cardiovascular diseases. However, the dynamics of such medium in physiological blood flow are poorly understood. Herein, we report a previously unnoticed dispersion pattern, which is a universal phenomenon, of a medium in pulsatile blood flow. We present a physical theory for studying the dispersion of a steadily injected heterogeneous medium into a thin tubular blood vessel in which the blood flow is pulsatile. In a thin tubular blood vessel, we demonstrate that variations of concentration associated with the heterogeneous medium obey a one-dimensional advection diffusion equation, and the diffusion has limited effect whenever a short vascular segment is considered. A distinct feature of the distribution of the medium in the axial distance-time plane is a "dilation-retraction" pattern. The time evolution signals at different axial positions exhibit distinct concentration waveforms. A numerical scheme is proposed for exploiting this information to estimate the pulsatile velocity. Artificial data are adopted to validate the scheme. Real X-ray angiography is also analyzed to support our theory and method. The theory is applicable whenever imaging protocols involve a heterogeneous medium in pulsatile flow.

A PULSATILE WILLIAMSON NANOFLUID FLOW WITH MOTILE MICROORGANISMS BETWEEN TWO PERMEABLE WALLS: EFFECT OF MODIFIED DARCY'S LAW

The aim of the proposed scheme is to look at the non-Newtonian Williamson magnetohydrodynamics (MHD) pulsatile movement of an incompressible nanofluid in the existence of motile microorganisms. The flow is saturated in porous media between two permeable vertical walls. The non-Newtonian fluid is described by employing the modified Darcy's law. An unchanged normal magnetic field pervades the structure to the walls. The novelty of the ongoing work originates from a desire to highlight the role played by microbes and bacteria, as well as nanoparticles in the use of significant pulsatile pump flow. The heat transmission, effects of viscous dissipation, and thermal radiation, in addition to volumetric nanoparticles fraction and microorganism concentration, are scrutinized. Regarding the pulsatile flow, each of the distributions is divided into two steady and oscillatory parts. The nonlinear fundamental equations are analyzed by means of the homotopy perturbation method (HPM). The impact of numerous physical restrictions is examined and depicted in a series of graphs. It is found that the existence of microorganisms obstructs the flow and reduces its speed. This infection can be avoided by reducing the parameters of buoyancy and bio-convection. All heat-related parameters are found as incremental factors of heat flux, which is an important phenomenon in many medical and engineering applications.

Ultrasound-guided radial artery cannulation: A report of a simple and low-cost model for training

IntroductionPracticing models for invasive procedure have proven useful in achieving better rates of success for physicians in training. Often, these models are not easy to get because of its expensive price. Radial artery cannulation is a common practice and its performance with ultrasonographic guidance has proven to be more efficient than traditional ways. We developed a low-cost practicing model that may aid physicians in training to master the ultrasound-guided radial artery cannulation technique and achieve better rates of success when performing this procedure. MethodsUsing ordinary materials such as a piece of pork ham and rubber torniquets, we were able to build a 3-vessel artery model with pulsatile flow. ResultsUltrasonographic imaging revealed a vessel-like material embedded inside the piece of ham. This material resembles an artery which can be punctured with an in-plane or out-of-plane technique and cannulated afterwards, either with a Seldinger or a modified Seldinger technique. Once cannulated, pulsatile flow can be obtained through the catheter used. ConclusionOur model building time was 30 minutes, and its price doesn’t exceed more than $7.50 USD. This model can be used by physicians in training to practice the cannulation of a radial artery using ultrasonographic guidance.

Prediction of vortex structures in pulsatile flow through S-bend arterial geometry with different stenosis levels

Arterial stenosis poses a high cardiovascular risk, and clinical intervention is needed when these stenoses grow beyond a specific limit. The study of vortex dynamics in these diseased arteries can be beneficial to understand its severity. Therefore, in the present work, we have investigated the flow structures in an S-bend arterial geometry with different levels of stenosis using a sharp interface immersed boundary method. We have observed an onset of Kelvin-Helmholtz-type vortex roll-up for higher degrees of stenoses. Fluctuations in the wall shear stress are observed for higher stenosis degrees. However, these fluctuations depend on the position and length of the stenosis. Newtonian and non-Newtonian Carreau fluids predict similar vortex structures, although minor differences in the Kelvin-Helmholtz vortex structures and associated fluctuations are observed in the diastolic phase. The Newtonian fluid predicts a slightly longer low time-averaged wall shear stress (≤0.5 Pa) region immediately after the stenosis compared with the Carreau fluid in the 58 % blockage S-bend artery.

Elliptic cross sections in blood flow regulation

&lt;abstract&gt;&lt;p&gt;Arterial deformations arise in blood flow when surrounding tissue invades the space available for a blood vessel to maintain its circular cross section, the most immediate effects being a reduction in blood flow and redistribution of shear stress. Here we consider deformations from circular to elliptic cross sections. Solution of this problem in steady flow is fairly straightforward. The focus in the present paper is on pulsatile flow where the change from circular to elliptic cross sections is associated with a transition in the character of the equations governing the flow from Bessel to Mathieu equations. The main aim of our study is to examine the hemodynamic consequences of the change from circular to elliptic cross sections and on possible implications of this change in blood flow regulation. The study of this problem has been hampered in the past because of difficulties involved in the solution of the governing equations. In the present study we describe methods we have used to overcome some of these difficulties and present a comprehensive set of results based on these methods. In particular, vessel deformation is examined under two different conditions relevant to blood flow regulation: (i) keeping cross sectional area constant and (ii) keeping cross sectional circumference constant. The results provide an important context for the mechanism of neurovascular control of blood flow under the pathological conditions of vessel deformation. The difficulty which has characterized this problem is that it involves elements of mathematics which are well outside the scope of a clinical/physiological study, while it actually involves clinical/physiological elements which are well outside the scope of a mathematical study. We hope that the context which we provide in this paper helps resolve this difficulty.&lt;/p&gt;&lt;/abstract&gt;

A 3-D Printed Optically Clear Rigid Diseased Carotid Bifurcation Arterial Mock Vessel Model for Particle Image Velocimetry Analysis in Pulsatile Flow

Abstract In recent years, blood flow analyses of diseased arterial mock vessels using particle image velocimetry (PIV) have been hampered by the inability to fabricate optically clear anatomical vessel models that realistically replicate the complex morphology of arterial vessels and provide highly resolved flow images of flow tracer particles. The aim of this paper is to introduce a novel approach for producing optically clear 3-D printed rigid anatomical arterial vessel models that are suitable for PIV analysis using a common 3-D inkjet printing process (using a Formlabs Form 2 3-D printer) and stock clear resin (RS-F2-GPCL-04). By matching the index of refraction (IOR) of the working fluid to the stock clear resin material, and by printing the part in a 45-deg print orientation, a clear anatomical model that allows clear visualization of flow tracer particles can be produced which yields highly resolved flow images for PIV analyses. However, a 45-deg print orientation increases the need for post-processing due to an increased amount of printed support material. During post-processing, the part must be wet sanded in several steps and surface finished with Novus Plastic Polish 3 Step System to achieve the final surface finish needed to yield high-resolution flow images. The mock arterial vessel model produced in this work is a 3-D printed diseased carotid bifurcation artery developed from CTA scan data. A PIV analysis was conducted on the developed mock arterial vessel model installed in a complex transient flow loop to assess the flow profiles within the model and the clarity of the model. A computational fluid dynamics (CFD) simulation was conducted on the same carotid bifurcation arterial geometry, and the results were used as a benchmark comparison for PIV results. The results obtained in this work show excellent promise for using the developed approach for developing 3-D printed anatomical vessel models for experimental PIV analyses. The fabrication methodology of the clear anatomical models, PIV results, and CFD results is described in detail.

TEVP model predictions of the pulsatile blood flow in 3D aneurysmal geometries

TEVP model predictions of the pulsatile blood flow in 3D aneurysmal geometries

Characterizing pulsatile blood flow in a specific carotid bifurcation: insights into hemodynamics and rheology models

&lt;abstract&gt; &lt;p&gt;This study uses laminar and turbulent flow models to investigate the blood flow dynamics in a specific carotid bifurcation. Pulsatile boundary conditions and the rigid carotid artery wall are considered. Three viscosity models describe the non-Newtonian blood behavior. The Fluent solver and the finite volume method solve the equations. Results show a Poiseuille-like flow in the common carotid artery (CCA), unaffected by the flow regime, viscosity model, or boundary conditions. The branching zone exhibits a C-shaped stagnation zone with low velocity and wall shear stress due to the CCA widening and ICA/ECA curvature. Strong secondary flow is observed in the carotid sinus; the flow is directed towards the inner wall with higher velocity in the internal carotid artery. Discrepancies between viscosity models are pronounced in laminar flow, particularly with the natural boundary conditions. The non-Newtonian blood behavior is more apparent in the laminar flow of the external carotid artery, especially with the second set of boundary conditions.&lt;/p&gt; &lt;/abstract&gt;

The Capacitive Sensing of the Pulsatile Liquid Flow—Investigation on a Physical Vascular Model

This article investigates a prospective capacitive sensing method for the measurement of physical characteristics of a pulsatile liquid flow. It was tested on a physical vascular model. The volume pulse wave sensor holds a high sensitivity and thus great potential in the field of industrial applications and also in biomedical applications where we also encounter a pulsating flow of blood. Two types of capacity sensors were developed and tested on our blood vessel model, currently used for the simulation of pulse wave propagation with the possibility of changes in vessel properties and many setups are reached for testing different pulse wave propagations. The newly developed capacitive sensor detects the capacity change of pulsating liquid flow in the vascular model. Data from the capacitive sensor are compared with two reference sensors, one for direct pressure sensing and the second for noncontact optical sensing of changes in diameter. The signal processing is used for all three types of sensors and analysis in the time and frequency domain to determine the accuracy. The use of capacitive sensors is promising since it can measure a negligible change in the diameter of the vessel in the range of tens of femtofarads (fF). We can confirm that the high precision measurement is dependent on the environment, which can cause the capacity change, but with proper shielding it can be eliminated.