The Experts below are selected from a list of 12195 Experts worldwide ranked by ideXlab platform
Cari M Whyne - One of the best experts on this subject based on the ideXlab platform.
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Patient Specific quantitative analysis of fracture fixation in the proximal femur implementing principal strain ratios method and experimental validation
Journal of Biomechanics, 2010Co-Authors: Eran Peleg, Maarten Beek, Leo Joskowicz, Rami Mosheiff, Meir Liebergall, Cari M WhyneAbstract:Computational Patient-Specific Modeling has the potential to yield powerful information for selection and planning of fracture treatments if it can be developed to yield results that are rapid, focused and coherent from a clinical perspective. In this study we introduce the utilization of a principal strain fixation ratio measure (SR) defined as the ratio of principal strains that develop in a fixated bone relative to the principal strains that develop in the same bone in an intact state. The SR field output variable is theoretically independent of load amplitude and also has a direct clinical interpretation with SRo 1 � a representing stress shielding and SR41 +b representing overstressed bone. A combined experimental and numerical study was performed with cadaveric proximal femora (n¼ 6) intact and following fracture fixation to quantify the performance of the SR variable in terms of accuracy and sensitivity to uncertainties in density–elasticity relationships and load amplitude as model input variables. For a given axial compressive force the SR field output variable was found to be less sensitive to changes in density–elasticity relationships and the response function to be more accurate than strain values themselves; errors were reduced by 44% on comparing SR with strain in the fixated model. In addition, the experimental data confirmed the assumption that the SR values behave independent of load amplitude. The load independent behavior of SR and its direct clinical interpretation may ultimately provide an appropriate and easily understood comparative computational measure to choose between Patient Specific fracture fixation alternatives.
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Patient Specific quantitative analysis of fracture fixation in the proximal femur implementing principal strain ratios method and experimental validation
Journal of Biomechanics, 2010Co-Authors: Eran Peleg, Maarten Beek, Leo Joskowicz, Rami Mosheiff, Meir Liebergall, Cari M WhyneAbstract:Computational Patient-Specific Modeling has the potential to yield powerful information for selection and planning of fracture treatments if it can be developed to yield results that are rapid, focused and coherent from a clinical perspective. In this study we introduce the utilization of a principal strain fixation ratio measure (SR) defined as the ratio of principal strains that develop in a fixated bone relative to the principal strains that develop in the same bone in an intact state. The SR field output variable is theoretically independent of load amplitude and also has a direct clinical interpretation with SR 1+b representing overstressed bone. A combined experimental and numerical study was performed with cadaveric proximal femora (n=6) intact and following fracture fixation to quantify the performance of the SR variable in terms of accuracy and sensitivity to uncertainties in density-elasticity relationships and load amplitude as model input variables. For a given axial compressive force the SR field output variable was found to be less sensitive to changes in density-elasticity relationships and the response function to be more accurate than strain values themselves; errors were reduced by 44% on comparing SR with strain in the fixated model. In addition, the experimental data confirmed the assumption that the SR values behave independent of load amplitude. The load independent behavior of SR and its direct clinical interpretation may ultimately provide an appropriate and easily understood comparative computational measure to choose between Patient Specific fracture fixation alternatives.
Natalia A. Trayanova - One of the best experts on this subject based on the ideXlab platform.
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image based reconstruction of three dimensional myocardial infarct geometry for Patient Specific Modeling of cardiac electrophysiology
Medical Physics, 2015Co-Authors: Eranga Ukwatta, Adityo Prakosa, Martin Rajchl, Hermenegild Arevalo, Farhad Pashakhanloo, James A. White, Albert C. Lardo, Elliot R. Mcveigh, Daniel A. Herzka, Natalia A. TrayanovaAbstract:Purpose: Accurate three-dimensional (3D) reconstruction of myocardial infarct geometry is crucial to Patient-Specific Modeling of the heart aimed at providing therapeutic guidance in ischemic cardiomyopathy. However, myocardial infarct imaging is clinically performed using two-dimensional (2D) late-gadolinium enhanced cardiac magnetic resonance (LGE-CMR) techniques, and a method to build accurate 3D infarct reconstructions from the 2D LGE-CMR images has been lacking. The purpose of this study was to address this need. Methods: The authors developed a novel methodology to reconstruct 3D infarct geometry from segmented low-resolution (Lo-res) clinical LGE-CMR images. Their methodology employed the so-called logarithm of odds (LogOdds) function to implicitly represent the shape of the infarct in segmented image slices as LogOdds maps. These 2D maps were then interpolated into a 3D image, and the result transformed via the inverse of LogOdds to a binary image representing the 3D infarct geometry. To assess the efficacy of this method, the authors utilized 39 high-resolution (Hi-res) LGE-CMR images, including 36 in vivo acquisitions of human subjects with prior myocardial infarction and 3 ex vivo scans of canine hearts following coronary ligation to induce infarction. The infarct was manually segmented by trained experts in each slice of the Hi-res images, and the segmented data were downsampled to typical clinical resolution. The proposed method was then used to reconstruct 3D infarct geometry from the downsampled images, and the resulting reconstructions were compared with the manually segmented data. The method was extensively evaluated using metrics based on geometry as well as results of electrophysiological simulations of cardiac sinus rhythm and ventricular tachycardia in individual hearts. Several alternative reconstruction techniques were also implemented and compared with the proposed method. Results: The accuracy of the LogOdds method in reconstructing 3D infarct geometry, as measured by the Dice similarity coefficient, was 82.10% ± 6.58%, a significantly higher value than those of the alternative reconstruction methods. Among outcomes of electrophysiological simulations with infarct reconstructions generated by various methods, the simulation results corresponding to the LogOdds method showed the smallest deviation from those corresponding to the manual reconstructions, as measured by metrics based on both activation maps and pseudo-ECGs. Conclusions: The authors have developed a novel method for reconstructing 3D infarct geometry from segmented slices of Lo-res clinical 2D LGE-CMR images. This method outperformed alternative approaches in reproducing expert manual 3D reconstructions and in electrophysiological simulations.
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methodology for image based reconstruction of ventricular geometry for Patient Specific Modeling of cardiac electrophysiology
Progress in Biophysics & Molecular Biology, 2014Co-Authors: Adityo Prakosa, Hermenegild Arevalo, Farhad Pashakhanloo, Albert C. Lardo, Elliot R. Mcveigh, Daniel A. Herzka, Peter Malamas, S Zhang, Henry R Halperin, Natalia A. TrayanovaAbstract:Patient-Specific Modeling of ventricular electrophysiology requires an interpolated reconstruction of the 3-dimensional (3D) geometry of the Patient ventricles from the low-resolution (Lo-res) clinical images. The goal of this study was to implement a processing pipeline for obtaining the interpolated reconstruction, and thoroughly evaluate the efficacy of this pipeline in comparison with alternative methods. The pipeline implemented here involves contouring the epi- and endocardial boundaries in Lo-res images, interpolating the contours using the variational implicit functions method, and merging the interpolation results to obtain the ventricular reconstruction. Five alternative interpolation methods, namely linear, cubic spline, spherical harmonics, cylindrical harmonics, and shape-based interpolation were implemented for comparison. In the thorough evaluation of the processing pipeline, Hi-res magnetic resonance (MR), computed tomography (CT), and diffusion tensor (DT) MR images from numerous hearts were used. Reconstructions obtained from the Hi-res images were compared with the reconstructions computed by each of the interpolation methods from a sparse sample of the Hi-res contours, which mimicked Lo-res clinical images. Qualitative and quantitative comparison of these ventricular geometry reconstructions showed that the variational implicit functions approach performed better than others. Additionally, the outcomes of electrophysiological simulations (sinus rhythm activation maps and pseudo-ECGs) conducted using models based on the various reconstructions were compared. These electrophysiological simulations demonstrated that our implementation of the variational implicit functions-based method had the best accuracy.
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methodology for Patient Specific Modeling of atrial fibrosis as a substrate for atrial fibrillation
Journal of Electrocardiology, 2012Co-Authors: Kathleen S Mcdowell, Fijoy Vadakkumpadan, Robert C Blake, Joshua Blauer, Gernot Plank, Rob S Macleod, Natalia A. TrayanovaAbstract:Personalized computational cardiac models are emerging as an important tool for studying cardiac arrhythmia mechanisms, and have the potential to become powerful instruments for guiding clinical anti-arrhythmia therapy. In this article, we present the methodology for constructing a Patient-Specific model of atrial fibrosis as a substrate for atrial fibrillation. The model is constructed from high-resolution late gadolinium-enhanced magnetic resonance imaging (LGE-MRI) images acquired in vivo from a Patient suffering from persistent atrial fibrillation, accurately capturing both the Patient's atrial geometry and the distribution of the fibrotic regions in the atria. Atrial fiber orientation is estimated using a novel image-based method, and fibrosis is represented in the Patient-Specific fibrotic regions as incorporating collagenous septa, gap junction reModeling, and myofibroblast proliferation. A proof-of-concept simulation result of reentrant circuits underlying atrial fibrillation in the model of the Patient's fibrotic atrium is presented to demonstrate the completion of methodology development.
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Image-Based Estimation of Ventricular Fiber Orientations for Personalized Modeling of Cardiac Electrophysiology
IEEE Transactions on Medical Imaging, 2012Co-Authors: Fijoy Vadakkumpadan, Hermenegild Arevalo, Can Ceritoglu, Michael Miller, Natalia A. TrayanovaAbstract:Technological limitations pose a major challenge to acquisition of myocardial fiber orientations for Patient-Specific Modeling of cardiac (dys)function and assessment of therapy. The objective of this project was to develop a methodology to estimate cardiac fiber orientations from in vivo images of Patient heart geometries. An accurate representation of ventricular geometry and fiber orientations was reconstructed, respectively, from high-resolution ex vivo structural magnetic resonance (MR) and diffusion tensor (DT) MR images of a normal human heart, referred to as the atlas. Ventricular geometry of a Patient heart was extracted, via semiautomatic segmentation, from an in vivo computed tomography (CT) image. Using image transformation algorithms, the atlas ventricular geometry was deformed to match that of the Patient. Finally, the deformation field was applied to the atlas fiber orientations to obtain an estimate of Patient fiber orientations. The accuracy of the fiber estimates was assessed using six normal and three failing canine hearts. The mean absolute difference between inclination angles of acquired and estimated fiber orientations was 15.4° . Computational simulations of ventricular activation maps and pseudo-ECGs in sinus rhythm and ventricular tachycardia indicated that there are no significant differences between estimated and acquired fiber orientations at a clinically observable level.
Eran Peleg - One of the best experts on this subject based on the ideXlab platform.
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Patient Specific quantitative analysis of fracture fixation in the proximal femur implementing principal strain ratios method and experimental validation
Journal of Biomechanics, 2010Co-Authors: Eran Peleg, Maarten Beek, Leo Joskowicz, Rami Mosheiff, Meir Liebergall, Cari M WhyneAbstract:Computational Patient-Specific Modeling has the potential to yield powerful information for selection and planning of fracture treatments if it can be developed to yield results that are rapid, focused and coherent from a clinical perspective. In this study we introduce the utilization of a principal strain fixation ratio measure (SR) defined as the ratio of principal strains that develop in a fixated bone relative to the principal strains that develop in the same bone in an intact state. The SR field output variable is theoretically independent of load amplitude and also has a direct clinical interpretation with SRo 1 � a representing stress shielding and SR41 +b representing overstressed bone. A combined experimental and numerical study was performed with cadaveric proximal femora (n¼ 6) intact and following fracture fixation to quantify the performance of the SR variable in terms of accuracy and sensitivity to uncertainties in density–elasticity relationships and load amplitude as model input variables. For a given axial compressive force the SR field output variable was found to be less sensitive to changes in density–elasticity relationships and the response function to be more accurate than strain values themselves; errors were reduced by 44% on comparing SR with strain in the fixated model. In addition, the experimental data confirmed the assumption that the SR values behave independent of load amplitude. The load independent behavior of SR and its direct clinical interpretation may ultimately provide an appropriate and easily understood comparative computational measure to choose between Patient Specific fracture fixation alternatives.
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Patient Specific quantitative analysis of fracture fixation in the proximal femur implementing principal strain ratios method and experimental validation
Journal of Biomechanics, 2010Co-Authors: Eran Peleg, Maarten Beek, Leo Joskowicz, Rami Mosheiff, Meir Liebergall, Cari M WhyneAbstract:Computational Patient-Specific Modeling has the potential to yield powerful information for selection and planning of fracture treatments if it can be developed to yield results that are rapid, focused and coherent from a clinical perspective. In this study we introduce the utilization of a principal strain fixation ratio measure (SR) defined as the ratio of principal strains that develop in a fixated bone relative to the principal strains that develop in the same bone in an intact state. The SR field output variable is theoretically independent of load amplitude and also has a direct clinical interpretation with SR 1+b representing overstressed bone. A combined experimental and numerical study was performed with cadaveric proximal femora (n=6) intact and following fracture fixation to quantify the performance of the SR variable in terms of accuracy and sensitivity to uncertainties in density-elasticity relationships and load amplitude as model input variables. For a given axial compressive force the SR field output variable was found to be less sensitive to changes in density-elasticity relationships and the response function to be more accurate than strain values themselves; errors were reduced by 44% on comparing SR with strain in the fixated model. In addition, the experimental data confirmed the assumption that the SR values behave independent of load amplitude. The load independent behavior of SR and its direct clinical interpretation may ultimately provide an appropriate and easily understood comparative computational measure to choose between Patient Specific fracture fixation alternatives.
Wei Sun - One of the best experts on this subject based on the ideXlab platform.
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2018-New insights into mitral heart valve prolapse after chordae rupture through fluid–structure interaction computational Modeling.pdf
2019Co-Authors: Andrés Caballero, Wenbin Mao, Charles Primiano, Sabet Hashim, Raymond Mckay, Wei SunAbstract:Mitral valve (MV) dynamics depends on a force balance across the mitral leaflets, the chordae tendineae, the mitral annulus, the papillary muscles and the adjacent ventricular wall. Chordae rupture disrupts the link between the MV and the left ventricle (LV), causing mitral regurgitation (MR), the most common valvular disease. In this study, a fluid-structure interaction (FSI) Modeling framework is implemented to investigate the impact of chordae rupture on the left heart (LH) dynamics and severity of MR. A control and seven chordae rupture LH models were developed to simulate a pathological process in which minimal chordae rupture precedes more extensive chordae rupture. Different non-eccentric and eccentric regurgitant jets were identified during systole. Cardiac efficiency was evaluated by the ratio of external stroke work. MV structural results showed that basal/strut chordae were the major load-bearing chordae. An increased number of ruptured chordae resulted in reduced basal/strut tension, but increased marginal/intermediate load. Chordae rupture in a Specific scallop did not necessarily involve an increase in the stress of the entire prolapsed leaflet. This work represents a further step towards Patient-Specific Modeling of pathological LH dynamics, and has the potential to improve our understanding of the biomechanical mechanisms and treatment of primary MR.
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New insights into mitral heart valve prolapse after chordae rupture through fluid-structure interaction computational Modeling.
Scientific Reports, 2018Co-Authors: Andrés Caballero, Wenbin Mao, Charles Primiano, Sabet Hashim, Raymond G. Mckay, Wei SunAbstract:Mitral valve (MV) dynamics depends on a force balance across the mitral leaflets, the chordae tendineae, the mitral annulus, the papillary muscles and the adjacent ventricular wall. Chordae rupture disrupts the link between the MV and the left ventricle (LV), causing mitral regurgitation (MR), the most common valvular disease. In this study, a fluid-structure interaction (FSI) Modeling framework is implemented to investigate the impact of chordae rupture on the left heart (LH) dynamics and severity of MR. A control and seven chordae rupture LH models were developed to simulate a pathological process in which minimal chordae rupture precedes more extensive chordae rupture. Different non-eccentric and eccentric regurgitant jets were identified during systole. Cardiac efficiency was evaluated by the ratio of external stroke work. MV structural results showed that basal/strut chordae were the major load-bearing chordae. An increased number of ruptured chordae resulted in reduced basal/strut tension, but increased marginal/intermediate load. Chordae rupture in a Specific scallop did not necessarily involve an increase in the stress of the entire prolapsed leaflet. This work represents a further step towards Patient-Specific Modeling of pathological LH dynamics, and has the potential to improve our understanding of the biomechanical mechanisms and treatment of primary MR.
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Patient Specific Modeling of biomechanical interaction in transcatheter aortic valve deployment
Journal of Biomechanics, 2012Co-Authors: Qian Wang, Eric Sirois, Wei SunAbstract:The objective of this study was to develop a Patient-Specific computational model to quantify the biomechanical interaction between the transcatheter aortic valve (TAV) stent and the stenotic aortic valve during TAV intervention. Finite element models of a Patient-Specific stenotic aortic valve were reconstructed from multi-slice computed tomography (MSCT) scans, and TAV stent deployment into the aortic root was simulated. Three initial aortic root geometries of this Patient were analyzed: (a) aortic root geometry directly reconstructed from MSCT scans, (b) aortic root geometry at the rapid right ventricle pacing phase, and (c) aortic root geometry with surrounding myocardial tissue. The simulation results demonstrated that stress, strain, and contact forces of the aortic root model directly reconstructed from MSCT scans were significantly lower than those of the model at the rapid ventricular pacing phase. Moreover, the presence of surrounding myocardium slightly increased the mechanical responses. Peak stresses and strains were observed around the calcified regions in the leaflets, suggesting the calcified leaflets helped secure the stent in position. In addition, these elevated stresses induced during TAV stent deployment indicated a possibility of tissue tearing and breakdown of calcium deposits, which might lead to an increased risk of stroke. The potential of paravalvular leak and occlusion of coronary ostia can be evaluated from simulated post-deployment aortic root geometries. The developed computational models could be a valuable tool for pre-operative planning of TAV intervention and facilitate next generation TAV device design.
Leo Joskowicz - One of the best experts on this subject based on the ideXlab platform.
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Patient Specific quantitative analysis of fracture fixation in the proximal femur implementing principal strain ratios method and experimental validation
Journal of Biomechanics, 2010Co-Authors: Eran Peleg, Maarten Beek, Leo Joskowicz, Rami Mosheiff, Meir Liebergall, Cari M WhyneAbstract:Computational Patient-Specific Modeling has the potential to yield powerful information for selection and planning of fracture treatments if it can be developed to yield results that are rapid, focused and coherent from a clinical perspective. In this study we introduce the utilization of a principal strain fixation ratio measure (SR) defined as the ratio of principal strains that develop in a fixated bone relative to the principal strains that develop in the same bone in an intact state. The SR field output variable is theoretically independent of load amplitude and also has a direct clinical interpretation with SRo 1 � a representing stress shielding and SR41 +b representing overstressed bone. A combined experimental and numerical study was performed with cadaveric proximal femora (n¼ 6) intact and following fracture fixation to quantify the performance of the SR variable in terms of accuracy and sensitivity to uncertainties in density–elasticity relationships and load amplitude as model input variables. For a given axial compressive force the SR field output variable was found to be less sensitive to changes in density–elasticity relationships and the response function to be more accurate than strain values themselves; errors were reduced by 44% on comparing SR with strain in the fixated model. In addition, the experimental data confirmed the assumption that the SR values behave independent of load amplitude. The load independent behavior of SR and its direct clinical interpretation may ultimately provide an appropriate and easily understood comparative computational measure to choose between Patient Specific fracture fixation alternatives.
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Patient Specific quantitative analysis of fracture fixation in the proximal femur implementing principal strain ratios method and experimental validation
Journal of Biomechanics, 2010Co-Authors: Eran Peleg, Maarten Beek, Leo Joskowicz, Rami Mosheiff, Meir Liebergall, Cari M WhyneAbstract:Computational Patient-Specific Modeling has the potential to yield powerful information for selection and planning of fracture treatments if it can be developed to yield results that are rapid, focused and coherent from a clinical perspective. In this study we introduce the utilization of a principal strain fixation ratio measure (SR) defined as the ratio of principal strains that develop in a fixated bone relative to the principal strains that develop in the same bone in an intact state. The SR field output variable is theoretically independent of load amplitude and also has a direct clinical interpretation with SR 1+b representing overstressed bone. A combined experimental and numerical study was performed with cadaveric proximal femora (n=6) intact and following fracture fixation to quantify the performance of the SR variable in terms of accuracy and sensitivity to uncertainties in density-elasticity relationships and load amplitude as model input variables. For a given axial compressive force the SR field output variable was found to be less sensitive to changes in density-elasticity relationships and the response function to be more accurate than strain values themselves; errors were reduced by 44% on comparing SR with strain in the fixated model. In addition, the experimental data confirmed the assumption that the SR values behave independent of load amplitude. The load independent behavior of SR and its direct clinical interpretation may ultimately provide an appropriate and easily understood comparative computational measure to choose between Patient Specific fracture fixation alternatives.