scholarly journals The Direct Incorporation of Perfusion Defect Information to Define Ischemia and Infarction in a Finite Element Model of the Left Ventricle

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Alexander I. Veress ◽  
George S. K. Fung ◽  
Taek-Soo Lee ◽  
Benjamin M. W. Tsui ◽  
Gregory A. Kicska ◽  
...  
Keyword(s):  
Finite Element ◽  
Left Ventricle ◽  
Image Data ◽  
Element Model ◽  
Border Zone ◽  
Average Intensity ◽  
Cardiac Image ◽  
Mechanical Models ◽  
Highly Correlated ◽  
Perfusion Maps

This paper describes the process in which complex lesion geometries (specified by computer generated perfusion defects) are incorporated in the description of nonlinear finite element (FE) mechanical models used for specifying the motion of the left ventricle (LV) in the 4D extended cardiac torso (XCAT) phantom to simulate gated cardiac image data. An image interrogation process was developed to define the elements in the LV mesh as ischemic or infarcted based upon the values of sampled intensity levels of the perfusion maps. The intensity values were determined for each of the interior integration points of every element of the FE mesh. The average element intensity levels were then determined. The elements with average intensity values below a user-controlled threshold were defined as ischemic or infarcted depending upon the model being defined. For the infarction model cases, the thresholding and interrogation process were repeated in order to define a border zone (BZ) surrounding the infarction. This methodology was evaluated using perfusion maps created by the perfusion cardiac-torso (PCAT) phantom an extension of the 4D XCAT phantom. The PCAT was used to create 3D perfusion maps representing 90% occlusions at four locations (left anterior descending (LAD) segments 6 and 9, left circumflex (LCX) segment 11, right coronary artery (RCA) segment 1) in the coronary tree. The volumes and shapes of the defects defined in the FE mechanical models were compared with perfusion maps produced by the PCAT. The models were incorporated into the XCAT phantom. The ischemia models had reduced stroke volume (SV) by 18–59 ml. and ejection fraction (EF) values by 14–50% points compared to the normal models. The infarction models, had less reductions in SV and EF, 17–54 ml. and 14–45% points, respectively. The volumes of the ischemic/infarcted regions of the models were nearly identical to those volumes obtained from the perfusion images and were highly correlated (R2 = 0.99).

scholarly journals Electromechanical feedback with reduced cellular connectivity alters electrical activity in an infarct injured left ventricle: a finite element model study

2012 ◽  
Vol 302 (1) ◽  
pp. H206-H214 ◽  
Author(s):  
Samuel T. Wall ◽  
Julius M. Guccione ◽  
Mark B. Ratcliffe ◽  
Joakim S. Sundnes
Keyword(s):  
Finite Element ◽  
Left Ventricle ◽  
Finite Element Model ◽  
Element Model ◽  
Physiological Model ◽  
Border Zone ◽  
Geometric Mesh ◽  
Model Study ◽  
Magnetic Resonance Imaging Mri ◽  
And Function

Myocardial infarction (MI) significantly alters the structure and function of the heart. As abnormal strain may drive heart failure and the generation of arrhythmias, we used computational methods to simulate a left ventricle with an MI over the course of a heartbeat to investigate strains and their potential implications to electrophysiology. We created a fully coupled finite element model of myocardial electromechanics consisting of a cellular physiological model, a bidomain electrical diffusion solver, and a nonlinear mechanics solver. A geometric mesh built from magnetic resonance imaging (MRI) measurements of an ovine left ventricle suffering from a surgically induced anteroapical infarct was used in the model, cycled through the cardiac loop of inflation, isovolumic contraction, ejection, and isovolumic relaxation. Stretch-activated currents were added as a mechanism of mechanoelectric feedback. Elevated fiber and cross fiber strains were observed in the area immediately adjacent to the aneurysm throughout the cardiac cycle, with a more dramatic increase in cross fiber strain than fiber strain. Stretch-activated channels decreased action potential (AP) dispersion in the remote myocardium while increasing it in the border zone. Decreases in electrical connectivity dramatically increased the changes in AP dispersion. The role of cross fiber strain in MI-injured hearts should be investigated more closely, since results indicate that these are more highly elevated than fiber strain in the border of the infarct. Decreases in connectivity may play an important role in the development of altered electrophysiology in the high-stretch regions of the heart.

Incorporation of Perfusion Information Into a Finite Element Model of the Left Ventricle

2011 ◽  
Author(s):  
A. I. Veress ◽  
G. S. K. Fung ◽  
B. M. W. Tsui ◽  
W. P. Segars ◽  
G. T. Gullberg
Keyword(s):  
Finite Element ◽  
Left Ventricle ◽  
Male Subject ◽  
Image Data ◽  
Element Model ◽  
Normal Male ◽  
Physiological Basis ◽  
Anatomical Structures ◽  
Pet Ct ◽  
Single Set

The 4D NCAT and XCAT phantoms have been found useful in the simulation of medical image data especially SPECT, PET, CT and more recently MRI. The phantoms provide realistic models of the anatomical structures and respiratory and cardiac motions of humans. When combined with accurate models of the physics and instrumentation involved in the imaging process, accurate and realistic simulation data that closely mimic those acquired from patients can be obtained. However, a limitation to the 4D NCAT/XCAT series of phantoms is that the cardiac motion incorporated in the NCAT/XCAT was based on a single set of gated tagged MRI data of a particular normal male subject so that the definitions of pathologies such as ischemia and infarction in the phantoms had no physiological basis. Our previous work sought to overcome this limitation by incorporating into the phantoms, a physiologically based finite-element (FE) mechanical model for the left ventricle (LV). These model was found to accurately simulate both the normal motion of the LV as well as abnormal motions due to ischemia [1] and infarction [2]. One of the primary limitations of these models is that they have overly simplistic geometries (Figure 1) representing the ischemic or infarcted regions.

A finite element model of the infarcted left ventricle

1983 ◽  
Vol 16 (1) ◽  
pp. 45-58 ◽  
Author(s):  
Alan Needleman ◽  
Stuart A. Rabinowitz ◽  
Daniel K. Bogen ◽  
Thomas A. McMahon
Keyword(s):  
Finite Element ◽  
Left Ventricle ◽  
Finite Element Model ◽  
Element Model

A Multi-Modality Image Data Collection Protocol for Full Body Finite Element Model Development

2009 ◽  
Author(s):  
F. Scott Gayzik ◽  
Craig A. Hamilton ◽  
Josh C. Tan ◽  
Craig McNally ◽  
Stefan M. Duma ◽  
...  
Keyword(s):  
Finite Element ◽  
Data Collection ◽  
Finite Element Model ◽  
Model Development ◽  
Image Data ◽  
Element Model ◽  
Full Body

scholarly journals Recruitment from Myosin Off State Steepens ESPVR in Finite Element Model of Left Ventricle

2019 ◽  
Vol 116 (3) ◽  
pp. 30a
Author(s):  
Charles K. Mann ◽  
Zhanqui Liu ◽  
Xiaoyan Zhang ◽  
Kenneth Campbell ◽  
Jonathan Wenk
Keyword(s):  
Finite Element ◽  
Left Ventricle ◽  
Finite Element Model ◽  
Element Model

scholarly journals First Finite Element Model of the Left Ventricle With Mitral Valve: Insights Into Ischemic Mitral Regurgitation

2010 ◽  
Vol 89 (5) ◽  
pp. 1546-1553 ◽  
Author(s):  
Jonathan F. Wenk ◽  
Zhihong Zhang ◽  
Guangming Cheng ◽  
Deepak Malhotra ◽  
Gabriel Acevedo-Bolton ◽  
...  
Keyword(s):  
Finite Element ◽  
Mitral Valve ◽  
Left Ventricle ◽  
Mitral Regurgitation ◽  
Finite Element Model ◽  
Element Model ◽  
Ischemic Mitral Regurgitation

scholarly journals Evaluating snow weak-layer failure parameters through inverse finite element modelling of shaking-platform experiments

2015 ◽  
Vol 15 (1) ◽  
pp. 119-134 ◽  
Author(s):  
E. A. Podolskiy ◽  
G. Chambon ◽  
M. Naaim ◽  
J. Gaume
Keyword(s):  
Finite Element ◽  
Fracture Initiation ◽  
Friction Angle ◽  
Element Model ◽  
Avalanche Forecasting ◽  
Weak Layer ◽  
Mechanical Models ◽  
Homogeneous Stress ◽  
Coulomb Failure Criterion ◽  
Snow Samples

Abstract. Snowpack weak layers may fail due to excess stresses of various natures, caused by snowfall, skiers, explosions or strong ground motion due to earthquakes, and lead to snow avalanches. This research presents a numerical model describing the failure of "sandwich" snow samples subjected to shaking. The finite element model treats weak layers as interfaces with variable mechanical parameters. This approach is validated by reproducing cyclic loading snow fracture experiments. The model evaluation revealed that the Mohr–Coulomb failure criterion, governed by cohesion and friction angle, was adequate to describe the experiments. The model showed the complex, non-homogeneous stress evolution within the snow samples and especially the importance of tension on fracture initiation at the edges of the weak layer, caused by dynamic stresses due to shaking. Accordingly, a simplified analytical solution, ignoring the inhomogeneity of tangential and normal stresses along the failure plane, may incorrectly estimate the shear strength of the weak layers. The values for "best fit" cohesion and friction angle were ≈1.6 kPa and 22.5–60°. These may constitute valuable first approximations in mechanical models used for avalanche forecasting.

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