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Moshe Brand

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Yoshinobu Onuma

Krishnaraj Rathod

Oliver Guttmann

Krishnaraj Rathod

Queen Mary, University of London

National Institutes of Health

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Papers by Moshe Brand

The effect of completeness of revascularization on event-free survival at one year in the arts trial

Journal of the American College of Cardiology, 2002

We sought to assess the relationship between completeness of revascularization and adverse events... more We sought to assess the relationship between completeness of revascularization and adverse events at one year in the ARTS (Arterial Revascularization Therapies Study) trial. BACKGROUND There is uncertainty to what extent degree of completeness of revascularization, using up-to-date techniques, influences medium-term outcome. METHODS After consensus between surgeon and cardiologist regarding the potential for equivalence in the completeness of revascularization, 1,205 patients with multivessel disease were randomly assigned to either bypass surgery or stent implantation. All baseline and procedural angiograms and surgical case-record forms were centrally assessed for completeness of revascularization. RESULTS Of 1,205 patients randomized, 1,172 underwent the assigned treatment. Complete data for review were available in 1,143 patients (97.5%). Complete revascularization was achieved in 84.1% of the surgically treated patients and 70.5% of the angioplasty patients (p Ͻ 0.001). After one year, the stented angioplasty patients with incomplete revascularization showed a significantly lower event-free survival than stented patients with complete revascularization (i.e., freedom from death, myocardial infarction, cerebrovascular accident and repeat revascularization) (69.4% vs. 76.6%; p Ͻ 0.05). This difference was due to a higher incidence of subsequent bypass procedures (10.0% vs. 2.0%; p Ͻ 0.05). Conversely, at one year, bypass surgery patients with incomplete revascularization showed only a marginally lower event-free survival rate than those with complete revascularization (87.8% vs. 89.9%). CONCLUSIONS Complete revascularization was more frequently accomplished by bypass surgery than by stent implantation. One year after bypass, there was no significant difference in event-free survival between surgically treated patients with complete revascularization and those with incomplete revascularization, but patients randomized to stenting with incomplete revascularization had a greater need for subsequent bypass surgery.

Computational Fluid Dynamics of Blood Flow in the Abdominal Aorta Post “Chimney” Endovascular Aneurysm Repair (ChEVAR)

Aortic Aneurysm, 2017

Abdominal aortic aneurysms (AAAs) are a significant cause of death in the Western world. Endovasc... more Abdominal aortic aneurysms (AAAs) are a significant cause of death in the Western world. Endovascular aneurysm repair (EVAR) is becoming the prevalently used procedure to repair AAAs (versus the traditional approach of open surgery). In cases of infrarenal AAAs, there is a risk of the renal arteries being blocked by the stent graft (SG) inserted to repair the aneurysm. In these cases, two additional SGs termed"chimney" stent grafts (CSGs) are inserted into the renal arteries in parallel with the main SG to exclude this hazard. In this study, the hemodynamics of an infrarenal AAA endovascularly repaired by a system of SGs using the "chimney" technique is investigated. Two AAA models are analyzed using computational fluid dynamics (CFD, Ansys Fluent)-a healthy abdominal aorta and an abdominal aorta post"chimney" endovascular aneurysm repair (ChEVAR) with a CSG inserted into each renal artery in parallel with the aortic SG. Results indicate that CSGs induce stagnation zones downstream the renal arteries yet mild and confined overall flow and wall shear stress (WSS) modifications. The flow regime remains principally laminar. The study findings indicate the limited hemodynamic modifications of the ChEVAR procedure and thus further support its merit.

ESDA2008-59341 the Scimed Radius TM Stent-Artery Interaction

Main cause of restenosis after balloon angioplasty is due to the stresses generated in the artery... more Main cause of restenosis after balloon angioplasty is due to the stresses generated in the artery as well as from the stent artery interaction. Understanding the factors that are involved in this interaction and the ability to evaluate the stresses that are formed in the artery, could help to lessen the number of failures. The goal of the present study is to develop computationally efficient analytical model for estimating the potential damage factor as the contact stresses, and to investigate their influence upon stent design, artery and plaque parameters. The artery was stipulated to be thick walled cylinder and its stress-strain state was determined from analytic solution of Lame problem. An analytic model based on the analysis of the beams deformation in the framework EulerBernoulli assumptions was formulated for the stent. The radial pressure, which is exerted on the inner surface of the artery, is assumed to be an average of contact stresses applied by the stent and the blood ...

The effect of stent graft curvature on the hemodynamic displacement force after abdominal aortic aneurysm endovascular repair

Royal Society Open Science

Endovascular aortic aneurysm repair is a minimally invasive procedure with low mortality and morb... more Endovascular aortic aneurysm repair is a minimally invasive procedure with low mortality and morbidity. Clinical studies have revealed that a displacement force (DF) can cause stent graft (SG) migration in some circumstances requiring repeated intervention. This study aims to determine the relationship between the SG curvature and the calculated DF from four patient-specific computational fluid dynamics models. The SG's curvature was defined according to the centrelines of the implanted SG's branches. The centrelines were defined as either intersecting or separated lines. The centreline curvature (CLC) metrics were calculated based on the local curvature radii and the distances from the centrelines of idealized straight branches. The average CLC value and average variation were calculated to represent the entire graft's curvature. These CLC calculations were compared, and the method that gave the best correlation to the calculated DF was found. The optimal correlation is...

Is t-Branch stent Appropriate for Different Patients with Thoracoabdominal Aortic Aneurysm?

Investigation of the radial stiffness of stents

An Attempt to develop a numerical toll for the Prediction of Stenosis in Arteriovenous Fistula for Hemodialysis

Resolution of human arm redundancy in point tasks by synthesizing two criteria

Tel-Aviv University

Abstract—The human arm may be considered to be a redundant mechanism given a pointing task. As a ... more Abstract—The human arm may be considered to be a redundant mechanism given a pointing task. As a result, multiple arm configurations can be used to complete a pointing task in which the tip of the index finger is brought to a preselected point in space. A kinematic model of the human arm with four degrees of freedom (DOF) and the synthesis of two criteria were developed as an analytical tool for studying position tasks. The two criteria were: (1) minimizing angular joint displacement (Minimal Angular Displacement (MAD)) and (2) averaging limits of the shoulder joint range (Joint Range Availability (JRA)). Joint angles predicted by a weighted model synthesizing the MAD and JRA models was linearly correlated (slope=0.97; r2=0.81) with experimental data compared to individual criteria (MAD slope=0.76; r2=0.67 or JRA slope=1; r2=0.56). The partial contributions to the synthesized criterion were 70 % MAD and 30 % JRA. Solving the inverse kinematics problem of articulated redundant serial...

Numerical Models of an Artery with a Net Structured Stent

IFMBE Proceedings, 2009

Main cause of restenosis after balloon angioplasty is due to the stresses generated in the artery... more Main cause of restenosis after balloon angioplasty is due to the stresses generated in the artery as well as from the stent artery interaction. Understanding the factors that are involved in this interaction, and the ability to evaluate the stresses that are formed in the artery, could help to lessen the number of failures. The goal of the present study is to develop computationally efficient numerical models for estimating the Damage Factor (DF) as the contact stresses, and to investigate their influence upon stent design, artery and plaque parameters. At first the artery was taken as a hollow cylinder with homogenous, linear elastic properties of the material. Later, the artery was taken as a two dissimilar layers model, with non-linear hyper-elastic properties. The variation in the Damage Factor value as a function of the mismatch between stent's and artery's diameters is nearly linear, and as much as the diameter of the artery increases, the Damage Factor for the same mismatch decreases. For arteries with 75% blocking and mismatch of 1mm, the Damage Factor is 3.8.

Blood Flow in the Abdominal Aorta Post 'Chimney' Endovascular Aneurysm Repair

Proceedings of The 9th EUROSIM Congress on Modelling and Simulation, EUROSIM 2016, The 57th SIMS Conference on Simulation and Modelling SIMS 2016, Dec 19, 2018

Aortic aneurysms are a main death cause in the elderly population throughout the western world. I... more Aortic aneurysms are a main death cause in the elderly population throughout the western world. In recent years, more aneurysm repairs are performed endovascularly using stent grafts (SGs) inserted into the aneurysm site through the arterial system (minimally invasive). In this study, we analyze the hemodynamics in an aneurysmatic abdominal aorta (AAA) endovascularly repaired by a stent graft (SG) system using the chimney technique. Computational fluid dynamics (CFD) is employed to study models of a healthy aorta versus an aorta post 'chimney' endovascular aneurysm repair (ChEVAR) using chimney stent grafts (CSG) inserted into each renal artery in parallel to the aortic SG. Results demonstrate that the presence of the CSGs results in stagnation regions and wall shear stress (WSS) modifications, yet the flow regime remains laminar. Thus, indicating the spatially contained effects of the ChEVAR technique and further supporting its merit.

Knee position sense: does the time interval at the target angle affect position accuracy?

Journal of Physical Therapy Science, 2017

This study examined whether the interval at the target angle during knee joint position sense (JP... more This study examined whether the interval at the target angle during knee joint position sense (JPS) affected reposition accuracy, and evaluated the consequence of this factor on test-retest reliability. [Subjects and Methods] Twenty healthy subjects participated in this study. Reposition ability was measured after the knee was placed at a target angle (ranging from 40° to 60°) for intervals of 3, 6, 9, and 12 seconds, in randomized order. Two trials were performed for each condition. The measurement was repeated after a week. The absolute error (AE) of each trial and average AE under each condition within the two measures were used for data analysis. [Results] No significant difference was found in comparing the AE or the average AE during all trials and between the two measures. Fair-to-good reliability was found for the AE results of all trials under the conditions of 3, 6, and 12 seconds. Poor reliability was found with time interval of 9 seconds. [Conclusion] The length of time needed to memorize the target angle during knee JPS test might affect test reliability. Practitioners can use this information when collecting JPS data.

Clinical, Hemodynamical and Mechanical Aspects of Aortic Aneurisms and Endovascular Repair

Author's Accepted Manuscript Numerical Models of net-structure Stents inserted into arteries

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Numerical models of net-structure stents inserted into arteries

Computers in biology and medicine, 2014

Restenosis is strongly attributed to stresses caused by stent-artery interactions generated in th... more Restenosis is strongly attributed to stresses caused by stent-artery interactions generated in the artery after balloon angioplasty. Numerical methods are often used to examine the stent-artery mechanical interactions. To overcome the extensive computational requirements demanded by these simulations, simplifications are needed. We introduce simplified models to calculate the mechanical interactions between net-structured stents and arteries, and discuss their validity and implications. 2D simplified numerical models are suggested, which allow cost effective assessment of arterial stresses and the potential damage factor (DF). In these models, several contact problems were solved for arteries with hyper elastic mechanical properties. Stresses were calculated for a large range of cases and for different numerical model types. The effects of model simplifications, oversizing mismatch and stenosis rate and length and symmetry on the resulting stresses were analyzed. Results obtained fr...

The Influence of Post Angioplasty Stent Implant Profile on Arterial Wall Stress

Volume 4: 12th International Conference on Advanced Vehicle and Tire Technologies; 4th International Conference on Micro- and Nanosystems, 2010

One of the main causes for post angioplasty arterial restenosis is the excessive stress induced i... more One of the main causes for post angioplasty arterial restenosis is the excessive stress induced in the arterial wall during and after the medical intervention. The closed stent is introduced in the artery wrapped around the deflated balloon catheter and is expanded in the final position by inflating the balloon. Unfortunately, this process also stretches the arterial wall. Additionally, for the stent to be successful, its diameter must be slightly larger than the diameter of the inflated artery. The stent is usually a dense mesh of interconnected beams. Therefore, it is often considered that it applies a constant pressure to the artery / stent interface. However, in reality each beam individually presses against the innermost layer of the artery (intima). The current study proposes a model, which predicts the arterial wall subsurface stress field due to individual stent beams. It was found that the local shape of the contact (beam cross section) plays an important role close to the ...

Synthesizing two criteria for redundancy resolution of human arm in point tasks

2011 Third World Congress on Nature and Biologically Inspired Computing, 2011

The human arm may be considered to be a redundant mechanism given a pointing task. As a result, m... more The human arm may be considered to be a redundant mechanism given a pointing task. As a result, multiple arm configurations can be used to complete a pointing task in which the tip of the index finger is brought to a preselected point in space. A kinematic model of the human arm with four degrees of freedom (DOF) and the synthesis of two criteria were developed as an analytical tool for studying position tasks. The two criteria were: (1) minimizing angular joint displacement (Minimal Angular Displacement (MAD)) and (2) averaging limits of the shoulder joint range (Joint Range Availability (JRA)). Joint angles predicted by a weighted model synthesizing the MAD and JRA models was linearly correlated (slope=0.97; r 2 =0.81) with experimental data compared to individual criteria (MAD slope=0.76; r 2 =0.67 or JRA slope=1; r 2 =0.56). The partial contributions to the synthesized criterion were 70% MAD and 30% JRA. Solving the inverse kinematics problem of articulated redundant serials mechanism such as the human or robotic arm has applications in fields of human-robot interaction and wearable robotics, ergonomics, and computer graphics animation.

Post-Angioplastic Contact Mechanics With Different Levels of Artherosclerotic Plaque

STLE/ASME 2010 International Joint Tribology Conference, 2010

The main goal of balloon angioplasty is to extend the active cross-section of a partly blocked ar... more The main goal of balloon angioplasty is to extend the active cross-section of a partly blocked artery. In the last stage of the medical operation, a metallic frame (stent) is introduced in the open space of the artery (lumen) and expanded to the desired diameter. It is generally accepted that some of the main causes of post-angioplasty restenosis are the global stresses induced in the artery by the expanding stent and the local interaction between the stent and the arterial wall. In a blocked artery a thick layer of hard plaque deposition usually covers a significant section of the wall. Therefore, to choose an appropriate stent and improve upon the angioplasty success rate, a fundamental understanding of the local interaction between the stent and the plaque, as well as between the stent and the healthy wall is vital. The goal of the present study is to find a correlation between the local thickness of the plaque layer, contact geometry and the stent/artery radial mismatch.

Blood Flow in a Healthy Abdominal Aorta Versus Configurations of Aneurysmatic Abdominal Aortas Post 'Chimney' Endovascular Repair

In recent years, more aortic aneurysm repairs are performed endovascularly using stent grafts (SG... more In recent years, more aortic aneurysm repairs are performed endovascularly using stent grafts (SGs). In this study, we analyze the hemodynamics in an aneurysmatic abdominal aorta (AAA) endovascularly repaired by a stent graft (SG) system using the chimney technique. Computational fluid dynamics (CFD) is employed to study models of a healthy aorta versus an aorta post 'chimney' endovascular aneurysm repair (ChEVAR) using chimney stent grafts (CSG). Results demonstrate that the presence of the CSGs results in stagnation regions and wall shear stress (WSS) modifications, yet the flow regime remains laminar.

Numerical analysis of the hemodynamics of an abdominal aortic aneurysm repaired using the endovascular chimney technique

2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2015

This paper presents a numerical analysis of the hemodynamics in an abdominal aorta (AA) with an a... more This paper presents a numerical analysis of the hemodynamics in an abdominal aorta (AA) with an aneurysm repaired by a stent graft (SG) system using the chimney technique. Computational fluid dynamics (CFD) simulations were conducted in a model of an AA repaired with a chimney stent graft (CSG) inserted into a renal artery parallel to an aortic SG and a model of a healthy AA. Comparing the simulation results of these two cases suggests that the presence of the CSG in the AA causes changes in average wall shear stress (WSS), potentially damaging recirculation zones, and additional changes in flow patterns.

The effect of completeness of revascularization on event-free survival at one year in the arts trial

Journal of the American College of Cardiology, 2002

We sought to assess the relationship between completeness of revascularization and adverse events... more We sought to assess the relationship between completeness of revascularization and adverse events at one year in the ARTS (Arterial Revascularization Therapies Study) trial. BACKGROUND There is uncertainty to what extent degree of completeness of revascularization, using up-to-date techniques, influences medium-term outcome. METHODS After consensus between surgeon and cardiologist regarding the potential for equivalence in the completeness of revascularization, 1,205 patients with multivessel disease were randomly assigned to either bypass surgery or stent implantation. All baseline and procedural angiograms and surgical case-record forms were centrally assessed for completeness of revascularization. RESULTS Of 1,205 patients randomized, 1,172 underwent the assigned treatment. Complete data for review were available in 1,143 patients (97.5%). Complete revascularization was achieved in 84.1% of the surgically treated patients and 70.5% of the angioplasty patients (p Ͻ 0.001). After one year, the stented angioplasty patients with incomplete revascularization showed a significantly lower event-free survival than stented patients with complete revascularization (i.e., freedom from death, myocardial infarction, cerebrovascular accident and repeat revascularization) (69.4% vs. 76.6%; p Ͻ 0.05). This difference was due to a higher incidence of subsequent bypass procedures (10.0% vs. 2.0%; p Ͻ 0.05). Conversely, at one year, bypass surgery patients with incomplete revascularization showed only a marginally lower event-free survival rate than those with complete revascularization (87.8% vs. 89.9%). CONCLUSIONS Complete revascularization was more frequently accomplished by bypass surgery than by stent implantation. One year after bypass, there was no significant difference in event-free survival between surgically treated patients with complete revascularization and those with incomplete revascularization, but patients randomized to stenting with incomplete revascularization had a greater need for subsequent bypass surgery.

Computational Fluid Dynamics of Blood Flow in the Abdominal Aorta Post “Chimney” Endovascular Aneurysm Repair (ChEVAR)

Aortic Aneurysm, 2017

Abdominal aortic aneurysms (AAAs) are a significant cause of death in the Western world. Endovasc... more Abdominal aortic aneurysms (AAAs) are a significant cause of death in the Western world. Endovascular aneurysm repair (EVAR) is becoming the prevalently used procedure to repair AAAs (versus the traditional approach of open surgery). In cases of infrarenal AAAs, there is a risk of the renal arteries being blocked by the stent graft (SG) inserted to repair the aneurysm. In these cases, two additional SGs termed"chimney" stent grafts (CSGs) are inserted into the renal arteries in parallel with the main SG to exclude this hazard. In this study, the hemodynamics of an infrarenal AAA endovascularly repaired by a system of SGs using the "chimney" technique is investigated. Two AAA models are analyzed using computational fluid dynamics (CFD, Ansys Fluent)-a healthy abdominal aorta and an abdominal aorta post"chimney" endovascular aneurysm repair (ChEVAR) with a CSG inserted into each renal artery in parallel with the aortic SG. Results indicate that CSGs induce stagnation zones downstream the renal arteries yet mild and confined overall flow and wall shear stress (WSS) modifications. The flow regime remains principally laminar. The study findings indicate the limited hemodynamic modifications of the ChEVAR procedure and thus further support its merit.

ESDA2008-59341 the Scimed Radius TM Stent-Artery Interaction

Main cause of restenosis after balloon angioplasty is due to the stresses generated in the artery... more Main cause of restenosis after balloon angioplasty is due to the stresses generated in the artery as well as from the stent artery interaction. Understanding the factors that are involved in this interaction and the ability to evaluate the stresses that are formed in the artery, could help to lessen the number of failures. The goal of the present study is to develop computationally efficient analytical model for estimating the potential damage factor as the contact stresses, and to investigate their influence upon stent design, artery and plaque parameters. The artery was stipulated to be thick walled cylinder and its stress-strain state was determined from analytic solution of Lame problem. An analytic model based on the analysis of the beams deformation in the framework EulerBernoulli assumptions was formulated for the stent. The radial pressure, which is exerted on the inner surface of the artery, is assumed to be an average of contact stresses applied by the stent and the blood ...

The effect of stent graft curvature on the hemodynamic displacement force after abdominal aortic aneurysm endovascular repair

Royal Society Open Science

Endovascular aortic aneurysm repair is a minimally invasive procedure with low mortality and morb... more Endovascular aortic aneurysm repair is a minimally invasive procedure with low mortality and morbidity. Clinical studies have revealed that a displacement force (DF) can cause stent graft (SG) migration in some circumstances requiring repeated intervention. This study aims to determine the relationship between the SG curvature and the calculated DF from four patient-specific computational fluid dynamics models. The SG's curvature was defined according to the centrelines of the implanted SG's branches. The centrelines were defined as either intersecting or separated lines. The centreline curvature (CLC) metrics were calculated based on the local curvature radii and the distances from the centrelines of idealized straight branches. The average CLC value and average variation were calculated to represent the entire graft's curvature. These CLC calculations were compared, and the method that gave the best correlation to the calculated DF was found. The optimal correlation is...

Is t-Branch stent Appropriate for Different Patients with Thoracoabdominal Aortic Aneurysm?

Investigation of the radial stiffness of stents

An Attempt to develop a numerical toll for the Prediction of Stenosis in Arteriovenous Fistula for Hemodialysis

Resolution of human arm redundancy in point tasks by synthesizing two criteria

Tel-Aviv University

Abstract—The human arm may be considered to be a redundant mechanism given a pointing task. As a ... more Abstract—The human arm may be considered to be a redundant mechanism given a pointing task. As a result, multiple arm configurations can be used to complete a pointing task in which the tip of the index finger is brought to a preselected point in space. A kinematic model of the human arm with four degrees of freedom (DOF) and the synthesis of two criteria were developed as an analytical tool for studying position tasks. The two criteria were: (1) minimizing angular joint displacement (Minimal Angular Displacement (MAD)) and (2) averaging limits of the shoulder joint range (Joint Range Availability (JRA)). Joint angles predicted by a weighted model synthesizing the MAD and JRA models was linearly correlated (slope=0.97; r2=0.81) with experimental data compared to individual criteria (MAD slope=0.76; r2=0.67 or JRA slope=1; r2=0.56). The partial contributions to the synthesized criterion were 70 % MAD and 30 % JRA. Solving the inverse kinematics problem of articulated redundant serial...

Numerical Models of an Artery with a Net Structured Stent

IFMBE Proceedings, 2009

Main cause of restenosis after balloon angioplasty is due to the stresses generated in the artery... more Main cause of restenosis after balloon angioplasty is due to the stresses generated in the artery as well as from the stent artery interaction. Understanding the factors that are involved in this interaction, and the ability to evaluate the stresses that are formed in the artery, could help to lessen the number of failures. The goal of the present study is to develop computationally efficient numerical models for estimating the Damage Factor (DF) as the contact stresses, and to investigate their influence upon stent design, artery and plaque parameters. At first the artery was taken as a hollow cylinder with homogenous, linear elastic properties of the material. Later, the artery was taken as a two dissimilar layers model, with non-linear hyper-elastic properties. The variation in the Damage Factor value as a function of the mismatch between stent's and artery's diameters is nearly linear, and as much as the diameter of the artery increases, the Damage Factor for the same mismatch decreases. For arteries with 75% blocking and mismatch of 1mm, the Damage Factor is 3.8.

Blood Flow in the Abdominal Aorta Post 'Chimney' Endovascular Aneurysm Repair

Proceedings of The 9th EUROSIM Congress on Modelling and Simulation, EUROSIM 2016, The 57th SIMS Conference on Simulation and Modelling SIMS 2016, Dec 19, 2018

Aortic aneurysms are a main death cause in the elderly population throughout the western world. I... more Aortic aneurysms are a main death cause in the elderly population throughout the western world. In recent years, more aneurysm repairs are performed endovascularly using stent grafts (SGs) inserted into the aneurysm site through the arterial system (minimally invasive). In this study, we analyze the hemodynamics in an aneurysmatic abdominal aorta (AAA) endovascularly repaired by a stent graft (SG) system using the chimney technique. Computational fluid dynamics (CFD) is employed to study models of a healthy aorta versus an aorta post 'chimney' endovascular aneurysm repair (ChEVAR) using chimney stent grafts (CSG) inserted into each renal artery in parallel to the aortic SG. Results demonstrate that the presence of the CSGs results in stagnation regions and wall shear stress (WSS) modifications, yet the flow regime remains laminar. Thus, indicating the spatially contained effects of the ChEVAR technique and further supporting its merit.

Knee position sense: does the time interval at the target angle affect position accuracy?

Journal of Physical Therapy Science, 2017

This study examined whether the interval at the target angle during knee joint position sense (JP... more This study examined whether the interval at the target angle during knee joint position sense (JPS) affected reposition accuracy, and evaluated the consequence of this factor on test-retest reliability. [Subjects and Methods] Twenty healthy subjects participated in this study. Reposition ability was measured after the knee was placed at a target angle (ranging from 40° to 60°) for intervals of 3, 6, 9, and 12 seconds, in randomized order. Two trials were performed for each condition. The measurement was repeated after a week. The absolute error (AE) of each trial and average AE under each condition within the two measures were used for data analysis. [Results] No significant difference was found in comparing the AE or the average AE during all trials and between the two measures. Fair-to-good reliability was found for the AE results of all trials under the conditions of 3, 6, and 12 seconds. Poor reliability was found with time interval of 9 seconds. [Conclusion] The length of time needed to memorize the target angle during knee JPS test might affect test reliability. Practitioners can use this information when collecting JPS data.

Clinical, Hemodynamical and Mechanical Aspects of Aortic Aneurisms and Endovascular Repair

Author's Accepted Manuscript Numerical Models of net-structure Stents inserted into arteries

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Numerical models of net-structure stents inserted into arteries

Computers in biology and medicine, 2014

Restenosis is strongly attributed to stresses caused by stent-artery interactions generated in th... more Restenosis is strongly attributed to stresses caused by stent-artery interactions generated in the artery after balloon angioplasty. Numerical methods are often used to examine the stent-artery mechanical interactions. To overcome the extensive computational requirements demanded by these simulations, simplifications are needed. We introduce simplified models to calculate the mechanical interactions between net-structured stents and arteries, and discuss their validity and implications. 2D simplified numerical models are suggested, which allow cost effective assessment of arterial stresses and the potential damage factor (DF). In these models, several contact problems were solved for arteries with hyper elastic mechanical properties. Stresses were calculated for a large range of cases and for different numerical model types. The effects of model simplifications, oversizing mismatch and stenosis rate and length and symmetry on the resulting stresses were analyzed. Results obtained fr...

The Influence of Post Angioplasty Stent Implant Profile on Arterial Wall Stress

Volume 4: 12th International Conference on Advanced Vehicle and Tire Technologies; 4th International Conference on Micro- and Nanosystems, 2010

One of the main causes for post angioplasty arterial restenosis is the excessive stress induced i... more One of the main causes for post angioplasty arterial restenosis is the excessive stress induced in the arterial wall during and after the medical intervention. The closed stent is introduced in the artery wrapped around the deflated balloon catheter and is expanded in the final position by inflating the balloon. Unfortunately, this process also stretches the arterial wall. Additionally, for the stent to be successful, its diameter must be slightly larger than the diameter of the inflated artery. The stent is usually a dense mesh of interconnected beams. Therefore, it is often considered that it applies a constant pressure to the artery / stent interface. However, in reality each beam individually presses against the innermost layer of the artery (intima). The current study proposes a model, which predicts the arterial wall subsurface stress field due to individual stent beams. It was found that the local shape of the contact (beam cross section) plays an important role close to the ...

Synthesizing two criteria for redundancy resolution of human arm in point tasks

2011 Third World Congress on Nature and Biologically Inspired Computing, 2011

The human arm may be considered to be a redundant mechanism given a pointing task. As a result, m... more The human arm may be considered to be a redundant mechanism given a pointing task. As a result, multiple arm configurations can be used to complete a pointing task in which the tip of the index finger is brought to a preselected point in space. A kinematic model of the human arm with four degrees of freedom (DOF) and the synthesis of two criteria were developed as an analytical tool for studying position tasks. The two criteria were: (1) minimizing angular joint displacement (Minimal Angular Displacement (MAD)) and (2) averaging limits of the shoulder joint range (Joint Range Availability (JRA)). Joint angles predicted by a weighted model synthesizing the MAD and JRA models was linearly correlated (slope=0.97; r 2 =0.81) with experimental data compared to individual criteria (MAD slope=0.76; r 2 =0.67 or JRA slope=1; r 2 =0.56). The partial contributions to the synthesized criterion were 70% MAD and 30% JRA. Solving the inverse kinematics problem of articulated redundant serials mechanism such as the human or robotic arm has applications in fields of human-robot interaction and wearable robotics, ergonomics, and computer graphics animation.

Post-Angioplastic Contact Mechanics With Different Levels of Artherosclerotic Plaque

STLE/ASME 2010 International Joint Tribology Conference, 2010

The main goal of balloon angioplasty is to extend the active cross-section of a partly blocked ar... more The main goal of balloon angioplasty is to extend the active cross-section of a partly blocked artery. In the last stage of the medical operation, a metallic frame (stent) is introduced in the open space of the artery (lumen) and expanded to the desired diameter. It is generally accepted that some of the main causes of post-angioplasty restenosis are the global stresses induced in the artery by the expanding stent and the local interaction between the stent and the arterial wall. In a blocked artery a thick layer of hard plaque deposition usually covers a significant section of the wall. Therefore, to choose an appropriate stent and improve upon the angioplasty success rate, a fundamental understanding of the local interaction between the stent and the plaque, as well as between the stent and the healthy wall is vital. The goal of the present study is to find a correlation between the local thickness of the plaque layer, contact geometry and the stent/artery radial mismatch.

Blood Flow in a Healthy Abdominal Aorta Versus Configurations of Aneurysmatic Abdominal Aortas Post 'Chimney' Endovascular Repair

In recent years, more aortic aneurysm repairs are performed endovascularly using stent grafts (SG... more In recent years, more aortic aneurysm repairs are performed endovascularly using stent grafts (SGs). In this study, we analyze the hemodynamics in an aneurysmatic abdominal aorta (AAA) endovascularly repaired by a stent graft (SG) system using the chimney technique. Computational fluid dynamics (CFD) is employed to study models of a healthy aorta versus an aorta post 'chimney' endovascular aneurysm repair (ChEVAR) using chimney stent grafts (CSG). Results demonstrate that the presence of the CSGs results in stagnation regions and wall shear stress (WSS) modifications, yet the flow regime remains laminar.

Numerical analysis of the hemodynamics of an abdominal aortic aneurysm repaired using the endovascular chimney technique

2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2015

This paper presents a numerical analysis of the hemodynamics in an abdominal aorta (AA) with an a... more This paper presents a numerical analysis of the hemodynamics in an abdominal aorta (AA) with an aneurysm repaired by a stent graft (SG) system using the chimney technique. Computational fluid dynamics (CFD) simulations were conducted in a model of an AA repaired with a chimney stent graft (CSG) inserted into a renal artery parallel to an aortic SG and a model of a healthy AA. Comparing the simulation results of these two cases suggests that the presence of the CSG in the AA causes changes in average wall shear stress (WSS), potentially damaging recirculation zones, and additional changes in flow patterns.