scholarly journals Simultaneous measurements of 3D wall shear stress and pulse wave velocity in the murine aortic arch

2021 ◽  
Vol 23 (1) ◽  
Author(s):  
Patrick Winter ◽  
Kristina Andelovic ◽  
Thomas Kampf ◽  
Jan Hansmann ◽  
Peter Michael Jakob ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Pulse Wave Velocity ◽  
Aortic Arch ◽  
Spatial Resolution ◽  
Temporal Resolution ◽  
Pulse Wave ◽  
High Spatial Resolution ◽  
High Temporal Resolution ◽  
4D Flow

Abstract Purpose Wall shear stress (WSS) and pulse wave velocity (PWV) are important parameters to characterize blood flow in the vessel wall. Their quantification with flow-sensitive phase-contrast (PC) cardiovascular magnetic resonance (CMR), however, is time-consuming. Furthermore, the measurement of WSS requires high spatial resolution, whereas high temporal resolution is necessary for PWV measurements. For these reasons, PWV and WSS are challenging to measure in one CMR session, making it difficult to directly compare these parameters. By using a retrospective approach with a flexible reconstruction framework, we here aimed to simultaneously assess both PWV and WSS in the murine aortic arch from the same 4D flow measurement. Methods Flow was measured in the aortic arch of 18-week-old wildtype (n = 5) and ApoE−/− mice (n = 5) with a self-navigated radial 4D-PC-CMR sequence. Retrospective data analysis was used to reconstruct the same dataset either at low spatial and high temporal resolution (PWV analysis) or high spatial and low temporal resolution (WSS analysis). To assess WSS, the aortic lumen was labeled by semi-automatically segmenting the reconstruction with high spatial resolution. WSS was determined from the spatial velocity gradients at the lumen surface. For calculation of the PWV, segmentation data was interpolated along the temporal dimension. Subsequently, PWV was quantified from the through-plane flow data using the multiple-points transit-time method. Reconstructions with varying frame rates and spatial resolutions were performed to investigate the influence of spatiotemporal resolution on the PWV and WSS quantification. Results 4D flow measurements were conducted in an acquisition time of only 35 min. Increased peak flow and peak WSS values and lower errors in PWV estimation were observed in the reconstructions with high temporal resolution. Aortic PWV was significantly increased in ApoE−/− mice compared to the control group (1.7 ± 0.2 versus 2.6 ± 0.2 m/s, p < 0.001). Mean WSS magnitude values averaged over the aortic arch were (1.17 ± 0.07) N/m2 in wildtype mice and (1.27 ± 0.10) N/m2 in ApoE−/− mice. Conclusion The post processing algorithm using the flexible reconstruction framework developed in this study permitted quantification of global PWV and 3D-WSS in a single acquisition. The possibility to assess both parameters in only 35 min will markedly improve the analyses and information content of in vivo measurements.

scholarly journals Decreased rotational flow and circumferential wall shear stress as early markers of descending aorta dilation in Marfan syndrome: a 4D flow CMR study

2019 ◽  
Vol 21 (1) ◽  
Author(s):  
A. Guala ◽  
G. Teixido-Tura ◽  
L. Dux-Santoy ◽  
C. Granato ◽  
A. Ruiz-Muñoz ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Pulse Wave Velocity ◽  
Marfan Syndrome ◽  
Pulse Wave ◽  
Rotational Flow ◽  
4D Flow ◽  
Descending Aorta ◽  
Early Markers ◽  
Wall Shear

Abstract Background Diseases of the descending aorta have emerged as a clinical issue in Marfan syndrome following improvements in proximal aorta surgical treatment and the consequent increase in life expectancy. Although a role for hemodynamic alterations in the etiology of descending aorta disease in Marfan patients has been suggested, whether flow characteristics may be useful as early markers remains to be determined. Methods Seventy-five Marfan patients and 48 healthy subjects were prospectively enrolled. In- and through-plane vortexes were computed by 4D flow cardiovascular magnetic resonance (CMR) in the thoracic aorta through the quantification of in-plane rotational flow and systolic flow reversal ratio, respectively. Regional pulse wave velocity and axial and circumferential wall shear stress maps were also computed. Results In-plane rotational flow and circumferential wall shear stress were reduced in Marfan patients in the distal ascending aorta and in proximal descending aorta, even in the 20 patients free of aortic dilation. Multivariate analysis showed reduced in-plane rotational flow to be independently related to descending aorta pulse wave velocity. Conversely, systolic flow reversal ratio and axial wall shear stress were altered in unselected Marfan patients but not in the subgroup without dilation. In multivariate regression analysis proximal descending aorta axial (p = 0.014) and circumferential (p = 0.034) wall shear stress were independently related to local diameter. Conclusions Reduced rotational flow is present in the aorta of Marfan patients even in the absence of dilation, is related to aortic stiffness and drives abnormal circumferential wall shear stress. Axial and circumferential wall shear stress are independently related to proximal descending aorta dilation beyond clinical factors. In-plane rotational flow and circumferential wall shear stress may be considered as an early marker of descending aorta dilation in Marfan patients.

A Technique for the Measurement of Wall Shear Stress Based on Micro Fabricated Hot-Film Sensor

2013 ◽  
Author(s):  
Takuya Sawada ◽  
Osamu Terashima ◽  
Yasuhiko Sakai ◽  
Kouji Nagata ◽  
Mitsuhiro Shikida ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Flows ◽  
Temporal Resolution ◽  
Large Scale ◽  
High Temporal Resolution ◽  
Film Sensor ◽  
Wall Shear ◽  
Hot Film ◽  
Hot Film Sensor

The objective of this study is to establish a technique for accurately measuring the wall shear stress in turbulent flows using a micro-fabricated hot-film sensor. Previously, we developed a hot-film sensor with a flexible polyimide-film substrate. This sensor can be attached to curved walls and be used in various situations. Furthermore, the sensor has a 20-μm-wide, heated thin metal film. However, the temporal resolution of this hot-film sensor is not very high owing to its substrate’s high heat capacity. Consequently, its performance is inadequate for measuring the wall shear stress “fluctuations” in turbulent flows. Therefore, we have developed another type of hot-film sensor in which the substrate is replaced with silicon, and a cavity has been introduced under the hot-film for reducing heat loss from the sensor and achieving high temporal resolution. Furthermore, for improving the sensor’s spatial resolution, the width of the hot-film is decreased to 10 μm. The structure of the hot-film’s pattern and the flow-detection mechanism are similar to those of the previous sensor. Experimental results show that new hot-film sensor works as expected and has better temporal resolution than the previous hot-film sensor. As future work, we will measure the wall shear stress for a turbulent wall-jet and discuss the relationship between a large-scale coherent vortex structure and wall shear stress based on data obtained using the new hot-film sensor.

scholarly journals Measurements of wall shear stress and aortic pulse wave velocity in swine with familial hypercholesterolemia

2014 ◽  
Vol 41 (5) ◽  
pp. 1475-1485 ◽  
Author(s):  
Andrew L. Wentland ◽  
Oliver Wieben ◽  
Dhanansayan Shanmuganayagam ◽  
Christian G. Krueger ◽  
Jennifer J. Meudt ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Pulse Wave Velocity ◽  
Familial Hypercholesterolemia ◽  
Wave Velocity ◽  
Pulse Wave ◽  
Aortic Pulse Wave Velocity ◽  
Wall Shear

scholarly journals An automatic contrail tracking algorithm

2010 ◽  
Vol 3 (4) ◽  
pp. 1089-1101 ◽  
Author(s):  
M. Vazquez-Navarro ◽  
H. Mannstein ◽  
B. Mayer
Keyword(s):  
Spatial Resolution ◽  
Temporal Resolution ◽  
High Spatial Resolution ◽  
High Temporal Resolution ◽  
Cirrus Cloud ◽  
Linear Stage ◽  
Geostationary Satellites ◽  
Rapid Scan ◽  
Temporal And Spatial ◽  
Resolution Data

Abstract. A method designed to track the life cycle of contrail-cirrus using satellite data with high temporal and spatial resolution, from its formation to the final dissolution of the aviation-induced cirrus cloud is presented. The method follows the evolution of contrails from their linear stage until they are undistinguishable from natural cirrus clouds. Therefore, the study of the effect of aircraft-induced clouds in the atmosphere is no longer restricted to linear contrails and can include contrail-cirrus. The method takes advantage of the high spatial resolution of polar orbiting satellites and the high temporal resolution of geostationary satellites to identify the pixels that belong to an aviation induced cloud. The high spatial resolution data of the MODIS sensor is used for contrail detection, and the high temporal resolution of the SEVIRI sensor in the Rapid Scan mode is used for contrail tracking. An example is included in which the method is applied to the study of a long lived contrail over the bay of Biscay.

scholarly journals Dual-satellite (Sentinel-2 and Landsat 8) remote sensing of supraglacial lakes in Greenland

2018 ◽  
Author(s):  
Andrew G. Williamson ◽  
Alison F. Banwell ◽  
Ian C. Willis ◽  
Neil S. Arnold
Keyword(s):  
Remote Sensing ◽  
Spatial Resolution ◽  
Temporal Resolution ◽  
High Spatial Resolution ◽  
Greenland Ice Sheet ◽  
High Temporal Resolution ◽  
Landsat 8 ◽  
Supraglacial Lakes ◽  
Dual Sensor ◽  
Sentinel 2

Abstract. Although remote sensing is commonly used to monitor supraglacial lakes on the Greenland Ice Sheet, most satellite records must trade-off high spatial resolution for high temporal resolution (e.g. MODIS) or vice versa (e.g. Landsat). Here, we overcome this issue by developing and applying a dual-sensor method that can monitor changes to lake areas and volumes at high spatial resolution (10–30 m) with a frequent revisit time (~ 3 days). We achieve this by mosaicking imagery from the Landsat 8 OLI with imagery from the recently launched Sentinel-2 MSI for a ~ 12 000 km2 area of West Greenland in summer 2016. First, we validate a physically based method for calculating lake depths with Sentinel-2 by comparing measurements against those derived from the available contemporaneous Landsat 8 imagery; we find close correspondence between the two sets of values (R2 = 0.841; RMSE = 0.555 m). This provides us with the methodological basis for automatically calculating lake areas, depths and volumes from all available Landsat 8 and Sentinel-2 images. These automatic methods are incorporated into an algorithm for Fully Automated Supraglacial lake Tracking at Enhanced Resolution (FASTER). The FASTER algorithm produces time series showing lake evolution during the 2016 melt season, including automated rapid (≤ 4 day) lake-drainage identification. With the dual Sentinel-2-Landsat 8 record, we identify 184 rapidly draining lakes, many more than identified with either imagery collection alone (93 with Sentinel-2; 66 with Landsat 8), due to their inferior temporal resolution, or would be possible with MODIS, due to its omission of small lakes 

scholarly journals Leaflets fusion length in bicuspid aortic valve is related to ascending and aortic root dilation and ascending aorta wall shear stress

2021 ◽  
Vol 22 (Supplement_1) ◽  
Author(s):  
A Guala ◽  
A Evangelista ◽  
L La Mura ◽  
G Teixido-Tura ◽  
L Dux-Santoy ◽  
...  
Keyword(s):  
Shear Stress ◽  
Aortic Valve ◽  
Wall Shear Stress ◽  
Stroke Volume ◽  
Pulse Wave Velocity ◽  
Healthy Volunteers ◽  
Wave Velocity ◽  
Aortic Root ◽  
Pulse Wave ◽  
Ascending Aorta

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Spanish Ministry of Science, Innovation and Universities, Instituto de Salud Carlos III Background Bicuspid aortic valve (BAV) is the most common congenital heart defect, consisting in the fusion of two aortic valve leaflets. Altered flow patterns have been related to aortic wall degeneration in BAV patients and may be responsible for the high prevalence of aortic disease in these patients. A number of studies on excised BAV or using advanced imaging modalities reported a wide variability of fusion extent between leaflet, but no previous study assessed whether leaflet fusion length may be used to stratify BAV patients. Purpose We aimed to test whether leaflet fusion extent can be quantified by cardiac magnetic resonance imaging (CMR) and whether it is related to aortic dilation and flow abnormalities in non-dysfunctional BAV. Methods One hundred and twenty BAV adults with no previous aortic or aortic valve surgery or significant valvular disease were consecutively enrolled. Patients with two sinuses of Valsalva (true BAV) or fusion of the left and non-coronary cusps, both being rare forms of BAV, were excluded. Twenty-eight healthy volunteers were also included for comparison. A 4D flow CMR sequence was acquired and circumferential wall shear stress and pulse wave velocity were assessed in the ascending aorta. A stack of double-oblique cine images of the aortic valve were used to quantify the length of the fusion between leaflets. Results The length of the fusion between leaflets was effectively measured in 112/120 patients (93%). Reproducibility was good (ICC = 0.826). Fusion length varied greatly (range 2.3 – 15.4 mm, 7.8 ± 3.2 mm, tertiles cut-off points were 6 and 9.3 mm). After correction for age, BSA, stroke volume and BAV fusion morphotype, fusion length was independently associated with diameter at the sinus of Valsalva (p = 0.002). Moreover, once corrected for age, stroke volume and ascending aorta pulse wave velocity, fusion length was positively related to ascending aorta diameter (p = 0.028). The comparison of maps of circumferential peak-systolic WSS in healthy volunteers (left) and BAV patients pertaining to the three leaflet fusion length tertiles is shown in Figure 1. Circumferential WSS progressively increase with larger fusion length. This trend was statistically significant (p &lt; 0.05) in the right and outer regions of the proximal and mid ascending aorta. Conclusions Bicuspid aortic leaflet fusion length varies considerably and it is independently associated with ascending aorta and aortic root dilation, possibly through flow alterations. Abstract Figure 1

scholarly journals Wall shear stress angle determines aortic growth in patients with bicuspid aortic valves

2021 ◽  
Vol 22 (Supplement_2) ◽  
Author(s):  
SCS Minderhoud ◽  
JW Roos-Hesselink ◽  
RG Chelu ◽  
LR Bons ◽  
AT Van Den Hoven ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Pulse Wave Velocity ◽  
Wave Velocity ◽  
Healthy Subjects ◽  
Pulse Wave ◽  
Independent Predictor ◽  
Ascending Aorta ◽  
Volumetric Growth ◽  
Aortic Valves

Abstract Funding Acknowledgements Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): The Dutch Heart Foundation Background Patients with bicuspid aortic valve (BAV) have altered flow velocity patterns with different wall shear stress (WSS) distributions in the ascending aorta compared to patients with tricuspid aortic valves. These WSS distributions are associated with aortic dilatation in cross sectional studies, however, longitudinal data demonstrating a potential causative role is missing. Purpose The aim of this study was to assess the differences in WSS distributions between BAV patients and healthy subjects and to determine the predictive value of WSS for aortic growth in patients with a BAV. Methods Forty patients with a BAV and 32 healthy matched subjects were prospectively studied by 4D-flow cardiovascular magnetic resonance (CMR). Peak velocity, pulse wave velocity, aortic distensibility, peak systolic WSS (magnitude), the different WSS components (axial and circumferential), and WSS angle were assessed in the proximal ascending aorta. WSS angle was defined as the angle between the WSSmagnitude and WSSaxial component. In the BAV patients, aortic volumetric growth over three years was determined in the proximal ascending aorta (first 5cm) based on CT angiography. Multivariate linear regression analysis was used to identify independent predictors of aortic volumetric growth. Results Of the BAV patients, 21 (53%) had a left-right fusion pattern and eight patients had Turner syndrome. WSSaxial was significantly lower in BAV patients compared to healthy subjects (p = 0.008) and WSScircumferential and WSS angle were significantly higher (both p &lt; 0.001, see Figure). WSSmagnitude, pulse wave velocity, and aorta distensibility were not statistically significant different. WSSmagnitude (0.69 N/m² [0.51-0.81] vs 1.08 N/m² [0.89-1.24], p = 0.005), WSSaxial (0.50 N/m² [0.39-0.61] vs 0.72 N/m²  [0.54-0.94], p = 0.015) and WSScircumferential (0.34 N/m² [0.32-0.46] vs 0.64 N/m² [0.47-0.81], p = 0.008) were significantly lower in BAV Turner patients compared to BAV non-Turner patients, while WSS angle (40° [34-41] vs 40° [32-48], p = 0.607) was not statistically significant different. During a follow-up of three years, there was a significant growth of the proximal ascending aorta in the BAV patients (1.2 cm3 [-0.2-2.5], p = 0.001). In multivariate analysis corrected for baseline aortic volume and diastolic blood pressure, WSS angle was the only independent predictor for proximal aortic volume growth (β=0.108, p = 0.030). Conclusions Increased WSScircumferential and especially WSS angle are present in patients with BAV. WSS angle was the only independent predictor of aortic growth. These findings highlight the potential role of  WSS measurements in patients with BAV to stratify patients at risk for aortic dilation.

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