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Electrophysiology Subject Specific Models. Darrell Swenson Scientific Computing and Imaging (SCI) Institute Cardiovascular Research and Training Institute (CVRTI) Department of Bioengineering Dr. Rob MacLeod. Cardiac Ischemia. Hearts are electrical organs
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Electrophysiology Subject Specific Models Darrell Swenson Scientific Computing and Imaging (SCI) Institute Cardiovascular Research and Training Institute (CVRTI) Department of Bioengineering Dr. Rob MacLeod
Cardiac Ischemia • Hearts are electrical organs • Electrical current causes heart contraction • Most heart failures are electrical • ECG’s show hearts electrical activity • Coronary Arteries supply blood to the heart. • Coronary blood flow provides the needed nutrients and ions • Conduction rate is dependent on blood flow.
Cardiac Ischemia • Ischemia is the lack of blood flow • The lack of blood flow changes the conductance. • Changes in conductance alter the activation wave. • This often leads to heart failure • These changes can be detected with an ECG • ECGs are insufficient to detect a large percentage of ischemia. • Comparable ischemic regions produce dramatically different ECG signals. • The cause could be Individual structure variability.
Subject Specific Modeling Problem Specific Models • Dynamic ischemic zone that changes based on experimental data. • Adaptive meshing based on fiber directions • Variable myocardial wall thickness Subject Specific Geometry • Shape of heart • Shape and time point of the ischemic region • Fiber orientation for anisotropic conduction
MRI Segmentation Surface Meshing 3D Meshing DTI Surface Potentials MRI • Small animal imaging facility • 7 tesla scanner • High resolution and DTI scans • Gd markers used for registration
MRI Segmentation Surfacing Meshing DTI Surface Potentials
Segmentation Surface Meshing MRI 3D Meshing DTI Surface Potentials Segmentation • Seg3D • Segment myocardium and ischemic region • Each segmentation requires a small amount of manual editing
Surface Meshing MRI Segmentation 3D Meshing DTI Surface Potentials Marching Cubes • SCIRun implementation • Smoothed with fairmesh algorithm • ~400,000 tris elements • Very detailed Particle System • Uses tetgen for surface • Not currently in SCIRun • Very detailed
Surface Meshing MRI Segmentation 3D Meshing DTI Surface Potentials
3D Meshing MRI Segmentation Surface Meshing DTI Surface Potentials Meshing • 1,400,000 Elements • Tetgen used for both marching cubes and particle system surfaces
3D Meshing MRI Segmentation Surface Meshing DTI Surface Potentials
DTI MRI Segmentation Surface Meshing 3D Meshing Surface Potentials Fiber Direction • Diffusion tensor imaging (DTI) • Anisotropic properties • Tensor interpolation
Surface Potentials MRI Segmentation Surface Meshing 3D Meshing DTI Ischemic Model • Bidomain model • Interactively adaptable ischemic zone • Segmented ischemic zones • Correlates to experimental results
Surface Potentials MRI Segmentation Surface Meshing 3D Meshing DTI Ischemic Model • Bidomain model • Interactively move ischemic zone • Segment ischemic zones • Correlate to lab results