Electrophysiology Subject Specific Models

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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

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Cardiac Ischemia

• Hearts are electrical organs
• Electrical current causes heart contraction
• Most heart failures are electrical
• ECGs 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.

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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.

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Subject Specific Modeling

• Subject Specific Geometry
• Shape of heart
• Shape and time point of the ischemic region
• Fiber orientation for anisotropic conduction

• Problem Specific Models
• Dynamic ischemic zone that changes based on
  experimental data.
• Adaptive meshing based on fiber directions
• Variable myocardial wall thickness

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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

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MRI
Segmentation
Surfacing
Meshing
DTI
Surface Potentials
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Segmentation
Surface Meshing
MRI
DTI
Surface Potentials
3D Meshing

• Segmentation
• Seg3D
• Segment myocardium and ischemic region
• Each segmentation requires a small amount of
  manual editing

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Surface Meshing
MRI
Segmentation
DTI
Surface Potentials
3D Meshing

• 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

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Surface Meshing
MRI
Segmentation
DTI
Surface Potentials
3D Meshing
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3D Meshing
MRI
Segmentation
DTI
Surface Potentials
Surface Meshing

• Meshing
• 1,400,000 Elements
• Tetgen used for both marching cubes and particle
  system surfaces

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3D Meshing
MRI
Segmentation
DTI
Surface Potentials
Surface Meshing
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DTI
MRI
Segmentation
Surface Potentials
Surface Meshing
3D Meshing

• Fiber Direction
• Diffusion tensor imaging (DTI)
• Anisotropic properties
• Tensor interpolation

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Surface Potentials
MRI
Segmentation
DTI
Surface Meshing
3D Meshing

• Ischemic Model
• Bidomain model
• Interactively adaptable ischemic zone
• Segmented ischemic zones
• Correlates to experimental results

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Surface Potentials
MRI
Segmentation
DTI
3D Meshing
Surface Meshing

• Ischemic Model
• Bidomain model
• Interactively move ischemic zone
• Segment ischemic zones
• Correlate to lab results

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• Thanks!