scholarly journals Patient-specific Hemodynamics of Severe Carotid Artery Stenosis Before and After Endarterectomy Examined by 4D Flow MRI

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Seungbin Ko ◽  
Jeesoo Lee ◽  
Simon Song ◽  
Doosang Kim ◽  
Sang Hyung Lee ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Carotid Artery Stenosis ◽  
Artery Stenosis ◽  
Patch Repair ◽  
Patient Specific ◽  
4D Flow Mri ◽  
4D Flow ◽  
Spatiotemporal Resolution ◽  
Before And After ◽  
Flow Mri

AbstractCarotid endarterectomy (CEA) influences the carotid endoluminal anatomy, which results in hemodynamic changes before and after surgery. We investigated the hemodynamics of severe carotid artery stenosis before and after conventional endarterectomy with/without patch repair. An in vitro experiment utilizing carotid phantoms, which underwent a procedure that emulated CEA with/without the patch repair, was performed with a high-spatiotemporal resolution using 4D flow MRI. We evaluated an abnormal region of carotids, which consists of the normalized time-averaged wall shear stress (NTA|WSS|) and the oscillatory shear index (OSI), to account for continuous high-shear regions (high NTA|WSS| and low OSI) and chaotic low-shear regions, i.e., stenosis-prone regions (low NTA|WSS| and high OSI). The use of normalized hemodynamic parameters (e.g., NTA|WSS|) allowed comparison of diverse cases with different conditions of hemodynamics and vessel geometry. We observed that the stenosis-prone regions of the carotids with patches were noticeably larger than the corresponding regions in no-patch carotids. A large recirculating flow zone found in the stenosis-prone region of the internal carotid artery (ICA) of the postoperative carotids with patches partially blocks the flow path into ICA, and consequently the flow rate was not recovered after surgery unlike an expectation.

scholarly journals Differences in Wall Shear Stress Between High-Risk and Low-Risk Plaques in Patients With Moderate Carotid Artery Stenosis: A 4D Flow MRI Study

2021 ◽  
Vol 15 ◽  
Author(s):  
Guiling Zhang ◽  
Shun Zhang ◽  
Yuanyuan Qin ◽  
Jicheng Fang ◽  
Xiangyu Tang ◽  
...  
Keyword(s):  
High Risk ◽  
Carotid Artery ◽  
Carotid Artery Stenosis ◽  
Cardiac Cycle ◽  
Low Risk ◽  
Artery Stenosis ◽  
4D Flow ◽  
Time Points ◽  
Flow Mri ◽  
The Difference

This study aimed to evaluate the difference in wall shear stress (WSS) (axial, circumferential, and 3D) between high-risk and low-risk plaques in patients with moderate carotid artery stenosis and to identify which time points and directions play the dominant roles in determining the risk associated with plaques. Forty carotid arteries in 30 patients were examined in this study. All patients underwent high-resolution vessel wall (HRVW) imaging, diffusion-weighted imaging (DWI), and 4D flow MRI; HRVW imaging and DWI were used to separate low- and high-risk plaque. Twenty-four high-risk plaques and 16 low-risk plaques were enrolled. An independent-sample t-test was used to compare WSS between low- and high-risk plaques in the whole cardiac cycle and at 20 different time points in the cardiac cycle. The study found that patients with high-risk plaques had higher WSS than those with low-risk plaques throughout the entire cardiac cycle (p < 0.05), but the changes varied at the 20 different time points. The number of non-significant differences (p > 0.05) was less in diastole than in systole across different time points. The axial WSS values were higher than the circumferential WSS values; the difference in axial WSS values between high- and low-risk plaques was more significant than the difference in circumferential WSS, whereas 3D WSS values best reflected the difference between high-risk and low-risk plaques because they showed significant differences at every time point. In conclusion, increased WSS, especially during the diastolic period and in the axial direction, may be a signal of a high-risk plaque and may cause cerebrovascular events in patients with moderate carotid artery stenosis. Additionally, WSS can provide hemodynamic information and help clinicians make more appropriate decisions for patients with plaques.

scholarly journals Enhancement of cerebrovascular 4D flow MRI velocity fields using machine learning and computational fluid dynamics simulation data

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
David R. Rutkowski ◽  
Alejandro Roldán-Alzate ◽  
Kevin M. Johnson
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Velocity Fields ◽  
Dynamics Simulation ◽  
Patient Specific ◽  
4D Flow Mri ◽  
4D Flow ◽  
Flow Phase ◽  
Flow Mri ◽  
Trained Network

AbstractBlood flow metrics obtained with four-dimensional (4D) flow phase contrast (PC) magnetic resonance imaging (MRI) can be of great value in clinical and experimental cerebrovascular analysis. However, limitations in both quantitative and qualitative analyses can result from errors inherent to PC MRI. One method that excels in creating low-error, physics-based, velocity fields is computational fluid dynamics (CFD). Augmentation of cerebral 4D flow MRI data with CFD-informed neural networks may provide a method to produce highly accurate physiological flow fields. In this preliminary study, the potential utility of such a method was demonstrated by using high resolution patient-specific CFD data to train a convolutional neural network, and then using the trained network to enhance MRI-derived velocity fields in cerebral blood vessel data sets. Through testing on simulated images, phantom data, and cerebrovascular 4D flow data from 20 patients, the trained network successfully de-noised flow images, decreased velocity error, and enhanced near-vessel-wall velocity quantification and visualization. Such image enhancement can improve experimental and clinical qualitative and quantitative cerebrovascular PC MRI analysis.

Abstract 14534: In vitro Assessment of Transvalvular Peak Velocity Measurement for Various Orifice Shapes: Comparison Between 4D Flow MRI vs. Doppler Echocardiography

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Jeesoo Lee ◽  
Nadia El hangouche ◽  
Liliana Ma ◽  
Michael Scott ◽  
Michael Markl ◽  
...  
Keyword(s):  
Temporal Resolution ◽  
Continuous Wave ◽  
Peak Velocity ◽  
Left Ventricular ◽  
Patient Specific ◽  
Maximal Velocity ◽  
4D Flow Mri ◽  
4D Flow ◽  
Flow Phantom ◽  
Flow Mri

Introduction: 4D flow MRI can assess transvalvular velocity, but validation against continuous wave (CW) Doppler echo is limited in high-velocity regurgitation and stenosis situations. We sought to compare 4D flow MRI and echo peak velocity using a pulsatile echo-MRI flow phantom. Materials and Methods: An MRI-compatible flow phantom with restrictive orifice situated was driven by a left ventricular assist device at 50 bpm (figure 1A). Three orifice shapes were tested: circular, elliptical and 3D-printed patient-specific mitral regurgitant orifice model of prolapse with areas of 0.5, 0.41 and 0.35 cm 2 , respectively. CW Doppler was acquired with peak velocity extracted from the profile. Retrospectively-gated 4D flow MRI was performed (spatial resolution = 2 mm isotropic, temporal resolution = 36 ms, encoding velocity = 400 cm/s). Maximal velocity magnitude was extracted volumetrically (figure 1B). An echo-mimicking profile was also obtained with a “virtual” ultrasound beam in the 4D flow data to simulate CW Doppler (figure 1C). Bland-Altman analysis was used to assess the agreement of temporal peak velocities. Results: 4D flow MRI demonstrated a centrally directed jet for the circular and elliptical orifices and an oblique jet for the prolapse orifice (figure 1B). Peak velocities were in excellent agreement between 4D flow MRI vs. echo for the circular (peak: 5.13 vs. 5.08 m/s, bias = 0.06 ± 0.66 m/s, figure 1D) and the elliptical orifice (peak: 4.95 vs. 4.79 m/s, bias = 0.07 ± 0.87 m/s, figure 1E). The prolapse orifice velocity was underestimated somewhat by MRI by ~10% (peak: 4.41 vs. 4.90 m/s, bias=0.26±1.18, figure 1F). Conclusion: 4D flow MRI can quantify high velocities like echo for simple geometries while underestimating for more complex geometry, likely due to partial volume effects. Further investigation is warranted to systematically investigate the effects of 4D flow MRI spatial and temporal resolution as well as the jet angle on velocity quantification accuracy.

scholarly journals Retinal Arterial Pressure Before and After Surgery for Carotid Artery Stenosis

Stroke ◽  
1971 ◽  
Vol 2 (6) ◽  
pp. 569-575 ◽  
Author(s):  
SHIGEAKI KOBAYASHI ◽  
ROBERT W. HOLLENHORST ◽  
THORALF M. SUNDT
Keyword(s):  
Carotid Artery ◽  
Arterial Pressure ◽  
Carotid Artery Stenosis ◽  
Artery Stenosis ◽  
Before And After

Abstract 14689: Regional Aortic Wall Shear Stress Mapping Implicates Hemodynamics in Human Bicuspid Aortopathy

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
David G Guzzardi ◽  
Pim van Ooij ◽  
Alex J Barker ◽  
Giampaolo Martufi ◽  
Katherine E Olsen ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Aortic Wall ◽  
Transforming Growth Factor ◽  
Patient Specific ◽  
4D Flow Mri ◽  
4D Flow ◽  
Hemodynamic Assessment ◽  
Flow Mri ◽  
Wall Shear

Introduction: A suspected genetic cause for bicuspid aortic valve (BAV) aortopathy has led to aggressive resection strategies. Using 4D flow MRI, we documented increased regional wall shear stress (WSS) in BAV patients. Local hemodynamics may exacerbate extracellular matrix (ECM) degradation leading to disease progression. If validated, preoperative regional hemodynamic assessment could be used to guide more targeted patient-specific aortic resection. For the first time, we correlated regional WSS with aortic tissue remodeling in BAV patients. Methods & Results: BAV patients (N=11) undergoing ascending aortic resection received preoperative 4D flow MRI with regional WSS differences mapped. Paired aortic wall samples (from same-patient with elevated WSS paired to normal WSS regions) were collected during surgery and compared using histology (pentachrome), biomechanics (biaxial mechanical testing), and ECM regulation (protein expression). Patient mean age: 49±18 years; mean aortic diameter: 4.6±0.7cm (range: 3.6 - 6.3cm); 55% had R+L fusion pattern; 36% had severe aortic stenosis. All patients had heterogeneous WSS patterns with regions of elevated WSS adjacent to those of normal WSS. By histology, regions of increased WSS showed greater medial elastin fragmentation, fibrosis, and cystic medial necrosis compared to adjacent areas of normal WSS. Regions of increased WSS showed increased elastic modulus (fold change±SD: 1.53±0.68; P=0.06, N=5) and collagen stiffness (1.37±0.49; P=0.07, N=5) compared to normal WSS regions suggesting altered distensibility. Multiplex protein analyses of ECM regulatory molecules revealed an increase in transforming growth factor β-1 (1.49±0.71, P=0.02), MMP-1 (1.62±0.84; P=0.01), MMP-2 (1.49±1.00; P=0.06), MMP-3 (1.23±0.36; P=0.02), MMP-7 (1.57±0.75; P=0.02), and TIMP-2 (1.26±0.33; P=0.01) in elevated WSS regions suggesting ECM dysregulation consistent with aortic remodeling. Conclusions: In BAV aorta, regional WSS corresponds with local histologic abnormalities, altered biomechanics, and ECM dysregulation. These novel data strongly implicate local hemodynamics as a mediator of BAV aortopathy. With further validation, 4D flow MRI could be used to guide personalized resection strategies.

TCD Evaluation Before and After Stenting in Patients With Severe Primary Carotid Artery Stenosis Versus Restenosis

2007 ◽  
Vol 14 (4) ◽  
pp. 483-488 ◽  
Author(s):  
Gregory Telman ◽  
Efim Kouperberg ◽  
Elliot Sprecher ◽  
Luis Gruberg ◽  
Rafael Beyar ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Carotid Artery Stenosis ◽  
Artery Stenosis ◽  
Before And After
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