The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform
Stéphane Avril - One of the best experts on this subject based on the ideXlab platform.
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Patient-specific computational evaluation of Stiffness distribution in ascending thoracic aortic aneurysm.
Journal of biomechanics, 2021Co-Authors: Marzio Di Giuseppe, Solmaz Farzaneh, Massimiliano Zingales, Salvatore Pasta, Stéphane AvrilAbstract:Abstract Quantifying local aortic Stiffness properties in vivo is acknowledged as essential to assess the severity of an ascending thoracic aortic aneurysm (ATAA). Recently, the LESI (local Extensional Stiffness identification) methodology has been established to quantify non-invasively local Stiffness properties of ATAAs using electrocardiographic-gated computed tomography (ECG-gated CT) scans. The aim of the current study was to determine the most sensitive markers of local ATAA Stiffness estimation with the hypothesis that direct measures of local ATAA Stiffness could better detect the high-risk patients. A cohort of 30 patients (12 BAV and 18 TAV) referred for aortic size evaluation by ECG-gated CT were recruited. For each patient, the Extensional Stiffness Q was evaluated by the LESI methodology whilst computational flow analyses were also performed to derive hemodynamics markers such as the wall shear stress (WSS). A strong positive correlation was found between the Extensional Stiffness and the aortic pulse pressure (R=0.644 and p
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Inverse identification of local Stiffness across ascending thoracic aortic aneurysms
Biomechanics and Modeling in Mechanobiology, 2019Co-Authors: Solmaz Farzaneh, Olfa Trabelsi, Stéphane AvrilAbstract:Aortic dissection is the most common catastrophe of the thoracic aorta, with a very high rate of mortality. Type A dissection is often associated with an ascending thoracic aortic aneurysm (ATAA). However, it is widely acknowledged that the risk of type A dissection cannot be reliably predicted simply by measuring the ATAA diameter and there is a pressing need for more reliable risk predictors. It was previously shown that there is a significant correlation between a rupture criterion based on the ultimate stretch of the ATAA and the local Extensional Stiffness of the aorta. Therefore, reconstructing regional variations of the Extensional Stiffness across the aorta appears highly important. In this paper, we present a novel noninvasive inverse method to identify the patient-specific local Extensional Stiffness of aortic walls based on preoperative gated CT scans. Using these scans, a structural mesh is defined across the aorta with a set of nodes attached to the same material points at different time steps throughout the cardiac cycle. For each node, time variations of the position are analyzed using Fourier series, permitting the reconstruction of the local strain distribution (fundamental term). Relating these strains to tensions with the Extensional Stiffness, and writing the local equilibrium satisfied by the tensions, the local Extensional Stiffness is finally derived at every position. The methodology is applied onto the ascending and descending aorta of three patients. Interestingly, the regional distribution of identified Stiffness properties appears heterogeneous across the ATAA. Averagely, the identified Stiffness is also compared with values obtained using other nonlocal methodologies. The results support the possible noninvasive prediction of stretch-based rupture criteria in clinical practice using local Stiffness reconstruction.
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Identifying Local Arterial Stiffness to Assess the Risk of Rupture of Ascending Thoracic Aortic Aneurysms
Annals of Biomedical Engineering, 2019Co-Authors: Solmaz Farzaneh, Olfa Trabelsi, Bertrand Chavent, Stéphane AvrilAbstract:It was recently submitted that the rupture risk of an ascending thoracic aortic aneurysm (ATAA) is strongly correlated with the aortic Stiffness. To validate this assumption, we propose a non-invasive inverse method to identify the patient-specific local Extensional Stiffness of aortic walls based on gated CT scans. Using these images, the local strain distribution is reconstructed throughout the cardiac cycle. Subsequently, obtained strains are related to tensions, through local equilibrium equations, to estimate the local Extensional Stiffness at every position. We apply the approach on 11 patients who underwent a gated CT scan before surgical ATAA repair and whose ATAA tissue was tested after the surgical procedure to estimate the rupture risk criterion. We find a very good correlation between the rupture risk criterion and the local Extensional Stiffness. Finally it is shown that patients can be separated in two groups: a group of stiff and brittle ATAA with a rupture risk criterion above 0.9, and a group of relatively compliant ATAA with a rupture risk below 0.9. Although these results need to be repeated on larger cohorts to impact the clinical practice, they support the paradigm that local aortic Stiffness is an important determinant of ATAA rupture risk.
Solmaz Farzaneh - One of the best experts on this subject based on the ideXlab platform.
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Patient-specific computational evaluation of Stiffness distribution in ascending thoracic aortic aneurysm.
Journal of biomechanics, 2021Co-Authors: Marzio Di Giuseppe, Solmaz Farzaneh, Massimiliano Zingales, Salvatore Pasta, Stéphane AvrilAbstract:Abstract Quantifying local aortic Stiffness properties in vivo is acknowledged as essential to assess the severity of an ascending thoracic aortic aneurysm (ATAA). Recently, the LESI (local Extensional Stiffness identification) methodology has been established to quantify non-invasively local Stiffness properties of ATAAs using electrocardiographic-gated computed tomography (ECG-gated CT) scans. The aim of the current study was to determine the most sensitive markers of local ATAA Stiffness estimation with the hypothesis that direct measures of local ATAA Stiffness could better detect the high-risk patients. A cohort of 30 patients (12 BAV and 18 TAV) referred for aortic size evaluation by ECG-gated CT were recruited. For each patient, the Extensional Stiffness Q was evaluated by the LESI methodology whilst computational flow analyses were also performed to derive hemodynamics markers such as the wall shear stress (WSS). A strong positive correlation was found between the Extensional Stiffness and the aortic pulse pressure (R=0.644 and p
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Inverse identification of local Stiffness across ascending thoracic aortic aneurysms
Biomechanics and Modeling in Mechanobiology, 2019Co-Authors: Solmaz Farzaneh, Olfa Trabelsi, Stéphane AvrilAbstract:Aortic dissection is the most common catastrophe of the thoracic aorta, with a very high rate of mortality. Type A dissection is often associated with an ascending thoracic aortic aneurysm (ATAA). However, it is widely acknowledged that the risk of type A dissection cannot be reliably predicted simply by measuring the ATAA diameter and there is a pressing need for more reliable risk predictors. It was previously shown that there is a significant correlation between a rupture criterion based on the ultimate stretch of the ATAA and the local Extensional Stiffness of the aorta. Therefore, reconstructing regional variations of the Extensional Stiffness across the aorta appears highly important. In this paper, we present a novel noninvasive inverse method to identify the patient-specific local Extensional Stiffness of aortic walls based on preoperative gated CT scans. Using these scans, a structural mesh is defined across the aorta with a set of nodes attached to the same material points at different time steps throughout the cardiac cycle. For each node, time variations of the position are analyzed using Fourier series, permitting the reconstruction of the local strain distribution (fundamental term). Relating these strains to tensions with the Extensional Stiffness, and writing the local equilibrium satisfied by the tensions, the local Extensional Stiffness is finally derived at every position. The methodology is applied onto the ascending and descending aorta of three patients. Interestingly, the regional distribution of identified Stiffness properties appears heterogeneous across the ATAA. Averagely, the identified Stiffness is also compared with values obtained using other nonlocal methodologies. The results support the possible noninvasive prediction of stretch-based rupture criteria in clinical practice using local Stiffness reconstruction.
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Identifying Local Arterial Stiffness to Assess the Risk of Rupture of Ascending Thoracic Aortic Aneurysms
Annals of Biomedical Engineering, 2019Co-Authors: Solmaz Farzaneh, Olfa Trabelsi, Bertrand Chavent, Stéphane AvrilAbstract:It was recently submitted that the rupture risk of an ascending thoracic aortic aneurysm (ATAA) is strongly correlated with the aortic Stiffness. To validate this assumption, we propose a non-invasive inverse method to identify the patient-specific local Extensional Stiffness of aortic walls based on gated CT scans. Using these images, the local strain distribution is reconstructed throughout the cardiac cycle. Subsequently, obtained strains are related to tensions, through local equilibrium equations, to estimate the local Extensional Stiffness at every position. We apply the approach on 11 patients who underwent a gated CT scan before surgical ATAA repair and whose ATAA tissue was tested after the surgical procedure to estimate the rupture risk criterion. We find a very good correlation between the rupture risk criterion and the local Extensional Stiffness. Finally it is shown that patients can be separated in two groups: a group of stiff and brittle ATAA with a rupture risk criterion above 0.9, and a group of relatively compliant ATAA with a rupture risk below 0.9. Although these results need to be repeated on larger cohorts to impact the clinical practice, they support the paradigm that local aortic Stiffness is an important determinant of ATAA rupture risk.
R.b. Moore - One of the best experts on this subject based on the ideXlab platform.
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Stiffness loss of synchronous belts
Composites Part B: Engineering, 1998Co-Authors: K.w. Dalgarno, Andrew J. Day, T.h.c. Childs, R.b. MooreAbstract:This paper considers the loss of Extensional Stiffness of synchronous belts through the life of the belt. It is shown experimentally that the belt Extensional Stiffness reduces initially with running time, before levelling out to remain constant. The Stiffness loss is considered to arise from the development of cracks in the cord which reinforces the belt. The cessation of this loss and the development of constant Stiffness is thought to arise from the cracks in the cord running out between the helically wound yarns in the cord, where the crack propagates either into the elastomer compound matrix or along the cord-elastomer compound interface. While this continues to undermine the strength of the belt, it does not serve to reduce the Stiffness of the cord or the belt.
K.w. Dalgarno - One of the best experts on this subject based on the ideXlab platform.
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Stiffness loss of synchronous belts
Composites Part B: Engineering, 1998Co-Authors: K.w. Dalgarno, Andrew J. Day, T.h.c. Childs, R.b. MooreAbstract:This paper considers the loss of Extensional Stiffness of synchronous belts through the life of the belt. It is shown experimentally that the belt Extensional Stiffness reduces initially with running time, before levelling out to remain constant. The Stiffness loss is considered to arise from the development of cracks in the cord which reinforces the belt. The cessation of this loss and the development of constant Stiffness is thought to arise from the cracks in the cord running out between the helically wound yarns in the cord, where the crack propagates either into the elastomer compound matrix or along the cord-elastomer compound interface. While this continues to undermine the strength of the belt, it does not serve to reduce the Stiffness of the cord or the belt.
Olfa Trabelsi - One of the best experts on this subject based on the ideXlab platform.
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Inverse identification of local Stiffness across ascending thoracic aortic aneurysms
Biomechanics and Modeling in Mechanobiology, 2019Co-Authors: Solmaz Farzaneh, Olfa Trabelsi, Stéphane AvrilAbstract:Aortic dissection is the most common catastrophe of the thoracic aorta, with a very high rate of mortality. Type A dissection is often associated with an ascending thoracic aortic aneurysm (ATAA). However, it is widely acknowledged that the risk of type A dissection cannot be reliably predicted simply by measuring the ATAA diameter and there is a pressing need for more reliable risk predictors. It was previously shown that there is a significant correlation between a rupture criterion based on the ultimate stretch of the ATAA and the local Extensional Stiffness of the aorta. Therefore, reconstructing regional variations of the Extensional Stiffness across the aorta appears highly important. In this paper, we present a novel noninvasive inverse method to identify the patient-specific local Extensional Stiffness of aortic walls based on preoperative gated CT scans. Using these scans, a structural mesh is defined across the aorta with a set of nodes attached to the same material points at different time steps throughout the cardiac cycle. For each node, time variations of the position are analyzed using Fourier series, permitting the reconstruction of the local strain distribution (fundamental term). Relating these strains to tensions with the Extensional Stiffness, and writing the local equilibrium satisfied by the tensions, the local Extensional Stiffness is finally derived at every position. The methodology is applied onto the ascending and descending aorta of three patients. Interestingly, the regional distribution of identified Stiffness properties appears heterogeneous across the ATAA. Averagely, the identified Stiffness is also compared with values obtained using other nonlocal methodologies. The results support the possible noninvasive prediction of stretch-based rupture criteria in clinical practice using local Stiffness reconstruction.
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Identifying Local Arterial Stiffness to Assess the Risk of Rupture of Ascending Thoracic Aortic Aneurysms
Annals of Biomedical Engineering, 2019Co-Authors: Solmaz Farzaneh, Olfa Trabelsi, Bertrand Chavent, Stéphane AvrilAbstract:It was recently submitted that the rupture risk of an ascending thoracic aortic aneurysm (ATAA) is strongly correlated with the aortic Stiffness. To validate this assumption, we propose a non-invasive inverse method to identify the patient-specific local Extensional Stiffness of aortic walls based on gated CT scans. Using these images, the local strain distribution is reconstructed throughout the cardiac cycle. Subsequently, obtained strains are related to tensions, through local equilibrium equations, to estimate the local Extensional Stiffness at every position. We apply the approach on 11 patients who underwent a gated CT scan before surgical ATAA repair and whose ATAA tissue was tested after the surgical procedure to estimate the rupture risk criterion. We find a very good correlation between the rupture risk criterion and the local Extensional Stiffness. Finally it is shown that patients can be separated in two groups: a group of stiff and brittle ATAA with a rupture risk criterion above 0.9, and a group of relatively compliant ATAA with a rupture risk below 0.9. Although these results need to be repeated on larger cohorts to impact the clinical practice, they support the paradigm that local aortic Stiffness is an important determinant of ATAA rupture risk.
