On the accuracy of viscous and turbulent loss quantification in stenotic aortic flow using phase‐contrast MRI

Binter, Christian; Gülan, Utku; Holzner, Markus; Kozerke, Sebastian

doi:10.1002/mrm.25862

Cited by 35 publications

(39 citation statements)

References 26 publications

(39 reference statements)

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“…Our finding that 4D Flow MRI underestimates PLVS is consistent with previous studies21363738. In contrast to the PLVS, PRSS was overestimated with increased voxel sizes.…”

Section: Discussionsupporting

confidence: 92%

“…This is because Reynolds stress estimation from 4D Flow MRI assumes that the velocity distribution within the voxel is Gaussian2728. Strong velocity gradients within the voxel resulting from local acceleration of the flow or the flow separation can result in intravoxel velocity distributions that differ from a Gaussian distribution2738. The overestimation of intravoxel velocity standard deviation (IVSD) and TKE near the vessel wall or jet flow has been observed in previous studies3739.…”

Section: Discussionmentioning

confidence: 92%

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Assessment of turbulent viscous stress using ICOSA 4D Flow MRI for prediction of hemodynamic blood damage

Lantz

Haraldsson

et al. 2016

Sci Rep

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Flow-induced blood damage plays an important role in determining the hemodynamic impact of abnormal blood flow, but quantifying of these effects, which are dominated by shear stresses in highly fluctuating turbulent flow, has not been feasible. This study evaluated the novel application of turbulence tensor measurements using simulated 4D Flow MRI data with six-directional velocity encoding for assessing hemodynamic stresses and corresponding blood damage index (BDI) in stenotic turbulent blood flow. The results showed that 4D Flow MRI underestimates the maximum principal shear stress of laminar viscous stress (PLVS), and overestimates the maximum principal shear stress of Reynolds stress (PRSS) with increasing voxel size. PLVS and PRSS were also overestimated by about 1.2 and 4.6 times at medium signal to noise ratio (SNR) = 20. In contrast, the square sum of the turbulent viscous shear stress (TVSS), which is used for blood damage index (BDI) estimation, was not severely affected by SNR and voxel size. The square sum of TVSS and the BDI at SNR >20 were underestimated by less than 1% and 10%, respectively. In conclusion, this study demonstrated the feasibility of 4D Flow MRI based quantification of TVSS and BDI which are closely linked to blood damage.

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“…Our finding that 4D Flow MRI underestimates PLVS is consistent with previous studies21363738. In contrast to the PLVS, PRSS was overestimated with increased voxel sizes.…”

Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 92%

Assessment of turbulent viscous stress using ICOSA 4D Flow MRI for prediction of hemodynamic blood damage

Lantz

Haraldsson

et al. 2016

Sci Rep

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“…Absolute quantification of flow and energy loss might be superior and more objective; furthermore, volumetric assessments might overcome limitatons of 2D analyses. However, validation using MRI, CFD, and particle image velocity data has only recently emerged, with mixed results relating to segmentation and resolution related errors 3536373839 . The computation of these parameters requires specialized algorithms and/or volumetric segmentations, neither of which were available for this study.…”

Section: Limitations Of the Studymentioning

confidence: 99%

Evaluation of Aortic Blood Flow and Wall Shear Stress in Aortic Stenosis and Its Association With Left Ventricular Remodeling

Knobelsdorff‐Brenkenhoff

Karunaharamoorthy

Trauzeddel

et al. 2016

Circ: Cardiovascular Imaging

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Background Aortic stenosis (AS) leads to variable stress for the left ventricle (LV) and consequently a broad range of LV remodeling. Study aim was to describe blood flow patterns in the ascending aorta of AS patients and determine their association with remodeling. Methods and Results Thirty-seven patients with AS (14 mild, 8 moderate, 15 severe; age 63±13 years) and 37 healthy controls (age 60±10 years) underwent 4D-flow MRI. Helical and vortical flow formations and flow eccentricity were assessed in the ascending aorta. Normalized flow displacement from the vessel center and peak systolic wall shear stress (WSSpeak) in the ascending aorta were quantified. LV remodeling was assessed based on LV mass index (LVMI-I) and the ratio of LV mass to enddiastolic volume (relative wall mass; RWM). Marked helical and vortical flow formation and eccentricity were more prevalent in patients with AS than in healthy subjects, and AS patients exhibited an asymmetric and elevated distribution of WSSpeak. In AS, aortic orifice area was strongly negatively associated with vortical flow formation (p=0.0274), eccentricity (p=0.0070) and flow displacement (p=0.0021). Bicuspid aortic valve was associated with more intense helical (p=0.0098) and vortical flow formation (p=0.0536), higher flow displacement (p=0.11) and higher WSSpeak (p=0.0926). LVM-I and RWM were significantly associated with aortic orifice area (p=0.0611, p=0.0058) and flow displacement (p=0.0058, p=0.0283). Conclusions In this pilot study, AS leads to abnormal blood flow pattern and WSSpeak in the ascending aorta. In addition to aortic orifice area, normalized flow displacement was significantly associated with LV remodeling.

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“…Viscous losses not related to turbulence also contribute to the total energy loss but have not been evaluated in this study. However, previous studies 19 showed that losses because of TKE exceeded nonturbulent viscous losses by a factor of 4 to 5 for moderate to severe stenosis, and currently used spatial resolutions are not sufficient for accurate viscous loss estimation.…”

Section: Study Limitationsmentioning

confidence: 94%

“…[14][15][16] Four-dimensional flow MRI also enables direct investigation of the mechanisms responsible for energy dissipation. 17,18 In particular, the assessment of turbulent kinetic energy (TKE)-the energy stored in turbulent flow-enables gauging energy losses caused by AS 19 because TKE is largely dissipated into heat. TKE can be quantified operator independently and reproducibly by 4D flow MRI, and it has been shown that TKE correlates with irreversible pressure loss as evidenced in a pilot study.…”

Section: Turbulent Kinetic Energy In Aortic Stenosismentioning

confidence: 99%

Turbulent Kinetic Energy Assessed by Multipoint 4-Dimensional Flow Magnetic Resonance Imaging Provides Additional Information Relative to Echocardiography for the Determination of Aortic Stenosis Severity

Binter

Gotschy

Sündermann

et al. 2017

Circ: Cardiovascular Imaging

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A ortic stenosis (AS) is the most prevalent valvular heart disease in adults of advanced age and, if untreated, is associated with a high mortality when symptoms occur. 1,2 According to current guidelines, the diagnosis of severe AS is based on echocardiographic measures of mean pressure gradient (MPG) and aortic valve effective orifice area (AVA). 3,4 Class I indications for valve replacement are severe, symptomatic AS or severe AS with reduced left ventricular ejection fraction.3,4 However, gauging symptoms of AS is highly subjective and can be confounded by various other diseases: for example, coronary artery disease, pulmonary disease, or orthopedic disorders. In addition, correct quantification of AS severity by 2-dimensional (2D) echocardiography is challenging, and AS severity is misclassified in a non-negligible portion of the patient population. [5][6][7][8] This misclassification has in part been associated with the effect of pressure recovery and its dependence on valve morphology and ascending aortic (AAo) diameter, which is not accounted for in standard echocardiographic metrics.An echocardiographic approach to correct for pressure recovery is the energy loss index (ELI), 9 which represents Background-Turbulent kinetic energy (TKE), assessed by 4-dimensional (4D) flow magnetic resonance imaging, is a measure of energy loss in disturbed flow as it occurs, for instance, in aortic stenosis (AS). This work investigates the additional information provided by quantifying TKE for the assessment of AS severity in comparison to clinical echocardiographic measures. Methods and Results-Fifty-one patients with AS (67±15 years, 20 female) and 10 healthy age-matched controls (69±5 years, 5 female) were prospectively enrolled to undergo multipoint 4D flow magnetic resonance imaging. Patients were split into 2 groups (severe and mild/moderate AS) according to their echocardiographic mean pressure gradient. TKE values were integrated over the aortic arch to obtain peak TKE. Integrating over systole yielded total TKE sys and by normalizing for stroke volume, normalized TKE sys was obtained. Mean pressure gradient and TKE correlated only weakly (R 2 =0.26 for peak TKE and R 2 =0.32 for normalized TKE sys ) in the entire study population including control subjects, while no significant correlation was observed in the AS patient group. In the patient population with dilated ascending aorta, both peak TKE and total TKE sys were significantly elevated (P<0.01), whereas mean pressure gradient was significantly lower (P<0.05). Patients with bicuspid aortic valves also showed significantly increased TKE metrics (P<0.01), although no significant difference was found for mean pressure gradient. Conclusions-Elevated TKE levels imply higher energy losses associated with bicuspid aortic valves and dilated ascending aortic geometries that are not assessable by current echocardiographic measures. These findings indicate that TKE may provide complementary information to echocardiography, helping to distinguish within the heterogeneo...

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On the accuracy of viscous and turbulent loss quantification in stenotic aortic flow using phase‐contrast MRI

Cited by 35 publications

References 26 publications

Assessment of turbulent viscous stress using ICOSA 4D Flow MRI for prediction of hemodynamic blood damage

Assessment of turbulent viscous stress using ICOSA 4D Flow MRI for prediction of hemodynamic blood damage

Evaluation of Aortic Blood Flow and Wall Shear Stress in Aortic Stenosis and Its Association With Left Ventricular Remodeling

Turbulent Kinetic Energy Assessed by Multipoint 4-Dimensional Flow Magnetic Resonance Imaging Provides Additional Information Relative to Echocardiography for the Determination of Aortic Stenosis Severity

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