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Journal ArticleDOI

A Spatiotemporal exploration and 3D modeling of blood flow in healthy carotid artery bifurcation from two modalities: Ultrasound-Doppler and phase contrast MRI.

TL;DR: The measured velocities showed that blood flow keeps a parabolic sectional profile distal from CCA, ECA and ICA, while being quite disturbed in the carotid sinus with a significant decrease in magnitude making this site very prone to atherosclerosis.
About: This article is published in Computers in Biology and Medicine.The article was published on 2020-03-01 and is currently open access. It has received 4 citations till now.

Summary (3 min read)

1. Introduction

  • Vascular maladies may be caused by thrombi and can lead to stroke [18].
  • Blood flow analysis can confirm the presence of a local vessel anomaly, its impact on the blood flow pattern and its possible evolution [7, 26, 25, 10].
  • Few studies compared velocity measurements in the carotid artery between US-Doppler and PC-MRI [15, 16, 38, 28].
  • Section 2 describes the imaging data sets and the analysis methodology.

2. Material and Methods

  • The arterial geometrical model was extracted from MR anatomical images and the hemodynamic modeling was performed from the obtained models.
  • The velocity waveforms from both PC-MRI and US-Doppler were extracted at three locations: the right CCA, ECA and ICA.

2.1.1. PC-MR imaging

  • The PC-MR images were acquired with a clinical 1.5 T Philips system (Ingenia, Philips medical systems, Best, the Netherlands) using 20 channels phased array head neck spine coil.
  • Fifty 2D anatomical images were acquired in axial orientation to cover cervical region Arij Debbich et al.: Preprint submitted to Elsevier Page 2 of 16 Figure 3: Growing carotid scanning windows size.
  • Key points are located in: CCA at 1.5 cm from the bifurcation, ECA and ICA: at 1 cm from the bifurcation.
  • The ideal velocity encoding (VENC) should be high enough to avoid aliasing and as low as possible to reduce velocity noise [47].
  • The total scan time for an exam was approximately 7 minutes.

2.1.2. US-Doppler imaging

  • All US-Doppler exams were conducted by a radiologist (B.H) with 10 years’ experience in cardiovascular imaging.
  • Clinical General Electric ultrasound systems (LOGIQ E9, GE Healthcare, Milwaukee, WI, USA) with 9 MHz linear probe were used.
  • US-Doppler images were matrices of dimension 720x960.
  • To extract the velocity waveform, the authors chose a profile of one cardiac cycle , fixed the two profile axes and selected 14 feature points on these profiles including PSV and EDV.
  • The USDoppler profile point digitization was performed using the Engauge Digitizer software [29].

2.2. PC-MRI Velocity profile extraction

  • Three velocity waveforms were extracted from PC-MRI at locations CCA, ECA, and ICA during a cardiac cycle which was divided into 14 time points.
  • The following values were deduced from the interpolated waveforms: - Velocity variation at a given pixel VMRIpixel .
  • - Maximum velocity at a given pixel within its eight neighbors VMRImax.-.
  • As the MRI and the US-Doppler examinations were not acquired at the same time, there might be some physiological variations [16].

2.3. Arterial model reconstruction and computational mesh generation

  • The geometrical characteristics of all the vessel segments for the ten subjects are given in Table1.
  • The carotid lumen was separated from the rest of the structures by applying an intensity threshold.
  • The model was further re-meshed using an Octree surface refinement based on prismatic wall [20].
  • Some studies adopted the rheological Newtonian behavior for the carotid artery (stationary viscosity) because it is simpler than the hemodynamic modeling with a non Newtonian behavior and arguing it has aminor impact on the results [33].

2.4. Boundary conditions

  • One of their objectives was to investigate the impact of the inlet boundary conditions on the simulation results.
  • These inlets were pulsed over time and were composed of the two usual physiological phases during a cardiac cycle: systole and diastole.
  • Velocity profile for every subject was matched to VMRImax inthe CCA, 3.3 cm from the carotid bifurcation to conform to the CCA dimension in the geometrical model.
  • (5) where ℎt is the maximal parabolic magnitude matching the VMRImax or VUS at time t. (xc , yc) and R are respectively thecenter coordinates and the radius of the CCA inlet section.
  • All meshes brought velocity profiles close to each other.

2.5. Simulated velocity profiles

  • Simulated velocity profiles Vsim were extracted at threelocations of the carotid bifurcation: 1.5 cm from the bifurcation in the CCA and 1 cm up the bifurcation in ECA and ICA.
  • The values were extracted using CFD-POST from ANSYS software.

3. Results

  • Velocity waveforms were extracted from PC-MRI (VMRImax, VMRIpixel and VMRImean) and Doppler-US (VUS)imaging data for ten volunteers at the three localizations of the carotid artery.
  • The first one, called VSIM_MRI, is based on PC-MRI data VMRImaxprofile used as inlet boundary condition.
  • The authors did not integrate the pixel-based PC-MRI velocity VMRIpixel in the tables since its values werebetween those of VMRImax and VMRImean and were noisier.

3.1. Analysis of PC-MRI velocities

  • Typical measured velocity waveforms from PC-MRI are presented in Figure 4. ECA and ICA relative to V MRImax for PC-MRI (up) and V US for US-Doppler (down).
  • The authors noted that a velocity profile over the CCA diameter at a given location was almost parabolic for all time points . and end diastolic (ED) time points every centimeter from the CCA to the carotid sinus, ICA and ECA .
  • There were significant variations de- tected in the carotid sinus site: a progressive decrease of the maximum velocity and a disruption of the profile shape.

3.2. Analysis of PC-MRI and US velocity measurements

  • Unlike the difference observed by Harloff et al.[15] for ICA, PSV of PC-MRI was on average less than US-Doppler by about 17.6%.
  • The same tendency was observed in CCA PSV (mean difference of 21.8 cm/s), to a much lower extent for CCA EDV .
  • Diastolic velocity profiles are less dissimilar except in ICA for the two modalities.
  • The mean velocity waveforms of the ten volunteers relative to PC-MRI and US-Doppler in CCA, ECA and ICA are plotted in Figure 10.

3.3. Analysis of simulated velocity waveforms

  • Overall, the numerical velocity waveforms were closer to the PC-MRI ones independent of the arterial input function considered (US or MRI).
  • The numerical velocities were compared to in vivo measurements through the global and the local indicators defined in section 3 .
  • The mean difference between measurements and simulation for PSV and EDV was greater.
  • From Tables 2, 3 and 4, it can be noted that the mean PSV of the ten subjects from VSIM_MRImax is lower than that from VSIM_US.

4. Discussion

  • The PC-MRI velocity behavior in the carotid bifurcation was investigated in time and space.
  • It was observed that the velocity estimation increased with the window size up to maximum .
  • This can be difficult to achieve when dealing with a PC-MRI and US-Doppler comparative study like ours for two reasons related to US measurements: i) lack of convenient accessibility for radiologists.
  • The arterial wall pulsatility has not been considered as it would have brought many additional issues with less mastered modeling methods (Fluid Structure Interaction).
  • Locally, the mean difference between VSIM_MRImax and VMRImax varied from 22% to 32% according to the local dif-ference metric at peak systole PSV and from 29% to 37%according to the local difference metric at end diastole EDV.

5. Conclusion

  • The authors investigated blood velocity quantification over the carotid artery bifurcation from PC-MRI and US-Doppler, and 3D velocity modeling from these modalities.
  • PC-MRI data analysis showed velocity across the section of the artery follows a parabolic profile except in the sinus region.
  • Overall, the authors found numerical velocities based on PC-MRI velocity inlet closer to measurements than those based on Doppler-US velocity inlet.
  • Therefore, from their experiments, the PC-MRI-based hemodynamic modeling approach could be reasonably more realistic.

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Citations
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TL;DR: In this paper, a wavy-walled arterial structure is simulated by applying a vorticity-stream function formulation approach. And the transformed dimensionless equations are further discretized using the finite difference method by developing the Peaceman-Rachford alternating direction implicit (P-R ADI) scheme.

4 citations

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TL;DR: In this article, the authors proposed a largeeddy simulation (LES) approach to carry out the hemodynamics and medication dispersion and deposition studies inside the descending aorta. And the analysis reveals that the flow separation causes a preferential deposition and build-up of low-density lipoproteins (LDL) on the arterial surface.
Abstract: The hemodynamics plays a key role in the transport processes, in the blood stream, and thus, on the accumulation and deposition of lipids and medication on the vessel’s wall. Therefore, understanding the hemodynamics of the arterial veins can advance the understanding of transport phenomena and prediction of deposition and buildup of the low-density lipoproteins (LDL) and particulate medication, on the arterial surfaces. Previous studies have showed that for pulsatile flow, laminar-turbulent flow transition may occur, particularly during intense exercises. Experimental and computational studies, of hemodynamics and transport phenomena, pose significant challenges due to the complex aorta’s geometry and arterial fluid dynamics. In the present study, we propose a large-eddy simulation (LES), computational approach, to carry out the hemodynamics and medication dispersion and deposition studies, inside the descending aorta. The analysis reveals that the flow separation causes a preferential deposition and build-up of low-density lipoproteins (LDL) on the arterial surface. Our study also shows that the flow boundary-layer separation is associated with an increase in deposition of the low-density lipoproteins. The analysis reveals the presence of Dean vortices, inside the aorta branches, which contribute to the reduction of the deposition and build-up of low-density lipoproteins on the arterial surfaces. The analysis of medication dispersion and deposition, inside the descending aorta, shows that the total medication deposition increases with the increase of particle size and density. Particles of fiber-like shape are more prone to deposition, and this is due to the fact that fiber-like particles align perfectly with the flow streamlines. Thus, the interaction of complex turbulent eddies with vessel’s wall causes medication deposition. The research shows that LES is a promising tool in the analysis of hemodynamics and medication transport and therefore, it may assist medical planning by providing surgeons with the elements of the blood flow such as, pressure, velocity, vorticity, wall-shear stresses, which cannot be measured in vivo and obtained with imaging techniques.

3 citations

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TL;DR: In this paper , simultaneous effects of tDCS on cerebral blood flow (CBF), venous blood oxygenation (Yv) and cerebral metabolic rate of oxygen (CMRO2) using simultaneous MRI in healthy adults to provide a reference frame for its neurobiological mechanisms.

1 citations

Journal ArticleDOI
TL;DR: The MRI‐based techniques that were used in the current study for measuring arterial flow in pediatric and adolescent patients demonstrated acceptable test‐retest reliability both at rest and immediately post‐exercise.
Abstract: Magnetic Resonance Imaging (MRI) is well‐suited for imaging peripheral blood flow due to its non‐invasive nature and excellent spatial resolution. Although MRI is routinely used in adults to assess physiological changes in chronic diseases, there are currently no MRI‐based data quantifying arterial flow in pediatric or adolescent populations during exercise. Therefore the current research sought to document femoral arterial blood flow at rest and following exercise in a pediatric‐adolescent population using phase contrast MRI, and to present test‐retest reliability data for this method. Ten healthy children and adolescents (4 male; mean age 14.8 ± 2.4 years) completed bloodwork and resting and exercise MRI. Baseline images consisted of PC‐MRI of the femoral artery at rest and following a 5 × 30 s of in‐magnet exercise. To evaluate test‐retest reliability, five participants returned for repeat testing. All participants successfully completed exercise testing in the MRI. Baseline flow demonstrated excellent reliability (ICC = 0.93, p = 0.006), and peak exercise and delta rest‐peak flow demonstrated good reliability (peak exercise ICC = 0.89, p = 0.002, delta rest‐peak ICC = 0.87, p = 0.003) between‐visits. All three flow measurements demonstrated excellent reliability when assessed with coefficients of variance (CV’s) (rest: CV = 6.2%; peak exercise: CV = 7.3%; delta rest‐peak: CV = 7.1%). The mean bias was small for femoral arterial flow. There was no significant mean bias between femoral artery flow visits 1 and 2 at peak exercise. There were no correlations between age or height and any of the flow measurements. There were no significant differences between male and female participants for any of the flow measurements. The current study determined that peripheral arterial blood flow in children and adolescents can be evaluated using non‐invasive phase contrast MRI. The MRI‐based techniques that were used in the current study for measuring arterial flow in pediatric and adolescent patients demonstrated acceptable test‐retest reliability both at rest and immediately post‐exercise.

1 citations

References
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01 Jan 1993-Stroke
TL;DR: In this paper, the prevalence of carotid stenosis and atherosclerosis in older adults with and without isolated systolic hypertension and to determine risk factors for Carotid artery disease in these two groups were determined.
Abstract: This study was designed to determine the prevalence of carotid stenosis and atherosclerosis in older adults with and without isolated systolic hypertension and to determine risk factors for carotid artery disease in these two groupsDuplex scans were performed on 187 participants of the Systolic Hypertension in the Elderly Program and on 187 normotensive control subjects Doppler measures of blood flow velocity were used to determine the prevalence of internal carotid artery stenosisCarotid stenosis was found in 25% of hypertensive participants but in only 7% of normotensive participants (p or = 160 mm Hg was the strongest predictor of carotid stenosis Other variables independently related to stenosis were diastolic blood pressure of or = 80 beats per minute (p =

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TL;DR: Pooled analysis suggests that WSS magnitudes obtained by 4D flow MRI are underestimated, while the relative distribution is reasonably accurate, the latter being an important factor for determining the natural history of intracranial aneurysms and other cerebrovascular diseases.

60 citations


"A Spatiotemporal exploration and 3D..." refers background in this paper

  • ...Several in vivo [15, 16, 28, 17, 30] , in vitro [45, 21, 2], in-silico [23, 19, 49, 33, 11], and mixed imageCFD (Computational Fluid Dynamics) [22, 36] approaches have focused on this artery and associated anomalies....

    [...]

Journal ArticleDOI
TL;DR: This study develops a proof-of-concept numerical procedure for constructing a simulated flow field that is influenced by both direct PC-MRI measurements and a fluid physics model, thereby taking advantage of both the accuracy of PC- MRI and the high spatial resolution of CFD.
Abstract: Phase contrast magnetic resonance imaging (PC-MRI) is used clinically for quantitative assessment of cardiovascular flow and function, as it is capable of providing directly-measured 3D velocity maps. Alternatively, vascular flow can be estimated from model-based computation fluid dynamics (CFD) calculations. CFD provides arbitrarily high resolution, but its accuracy hinges on model assumptions, while velocity fields measured with PC-MRI generally do not satisfy the equations of fluid dynamics, provide limited resolution, and suffer from partial volume effects. The purpose of this study is to develop a proof-of-concept numerical procedure for constructing a simulated flow field that is influenced by both direct PC-MRI measurements and a fluid physics model, thereby taking advantage of both the accuracy of PC-MRI and the high spatial resolution of CFD. The use of the proposed approach in regularizing 3D flow fields is evaluated. The proposed algorithm incorporates both a Newtonian fluid physics model and a linear PC-MRI signal model. The model equations are solved numerically using a modified CFD algorithm. The numerical solution corresponds to the optimal solution of a generalized Tikhonov regularization, which provides a flow field that satisfies the flow physics equations, while being close enough to the measured PC-MRI velocity profile. The feasibility of the proposed approach is demonstrated on data from the carotid bifurcation of one healthy volunteer, and also from a pulsatile carotid flow phantom. The proposed solver produces flow fields that are in better agreement with direct PC-MRI measurements than CFD alone, and converges faster, while closely satisfying the fluid dynamics equations. For the implementation that provided the best results, the signal-to-error ratio (with respect to the PC-MRI measurements) in the phantom experiment was 6.56 dB higher than that of conventional CFD; in the in vivo experiment, it was 2.15 dB higher. The proposed approach allows partial or complete measurements to be incorporated into a modified CFD solver, for improving the accuracy of the resulting flow fields estimates. This can be used for reducing scan time, increasing the spatial resolution, and/or denoising the PC-MRI measurements.

59 citations


"A Spatiotemporal exploration and 3D..." refers background or methods in this paper

  • ...ii) measurements of blood flow velocity (Ultrasound Doppler (US-Doppler) [46] or phase contrast Magnetic Resonance (PC-MRI) [41]) to provide at least arterial input functions....

    [...]

  • ...Realistic image-based patient specific CFDmodeling requires the extraction of several pieces of information from medical data with at least: i) the vascular morphology frommedical imaging (Computed tomographyAngiography (CTA) [43] orMagnetic Resonance Imaging (MRI) [41])....

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TL;DR: This work analyzes PIV-measured flow velocities in normal and stenosed carotid artery bifurcation models and demonstrates two quantitative measures of the flow complexity through the power-law decay slope of the energy spectrum and the global entropy.

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"A Spatiotemporal exploration and 3D..." refers background in this paper

  • ...Several in vivo [15, 16, 28, 17, 30] , in vitro [45, 21, 2], in-silico [23, 19, 49, 33, 11], and mixed imageCFD (Computational Fluid Dynamics) [22, 36] approaches have focused on this artery and associated anomalies....

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TL;DR: This work demonstrated that the proposed downstream peripheral vascular impedance model can be used for computational modelling when the outlets boundary conditions are not available, and successfully presented the potential of using medical imaging and numerical simulation to provide existing clinical prerequisites for diagnosis and therapeutic treatment.
Abstract: The study of cardiovascular models was presented in this paper based on medical image reconstruction and computational fluid dynamics. Our aim is to provide a reality platform for the purpose of flow analysis and virtual intervention outcome predication for vascular diseases. By connecting two porous mediums with transient permeability at the downstream of the carotid bifurcation branches, a downstream peripheral impedance model was developed, and the effect of the downstream vascular bed impedance can be taken into consideration. After verifying its accuracy with a healthy carotid bifurcation, this model was implemented in a diseased carotid bifurcation analysis. On the basis of time-averaged wall shear stress, oscillatory shear index, and the relative residence time, fractions of abnormal luminal surface were highlighted, and the atherosclerosis was assessed from a hemodynamic point of view. The effect of the atherosclerosis on the transient flow division between the two branches because of the existence of plaque was also analysed. This work demonstrated that the proposed downstream peripheral vascular impedance model can be used for computational modelling when the outlets boundary conditions are not available, and successfully presented the potential of using medical imaging and numerical simulation to provide existing clinical prerequisites for diagnosis and therapeutic treatment.

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"A Spatiotemporal exploration and 3D..." refers background or result in this paper

  • ...Several in vivo [15, 16, 28, 17, 30] , in vitro [45, 21, 2], in-silico [23, 19, 49, 33, 11], and mixed imageCFD (Computational Fluid Dynamics) [22, 36] approaches have focused on this artery and associated anomalies....

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  • ...This observation agrees with several CFD simulations in previous works [37, 40, 11, 12]....

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