EVARSim - Endovascular Aneurysm Repair Simulation Extension

A 3D Slicer extension for simulating endovascular stent placement along vessel centerlines, specifically designed for EVAR (Endovascular Aneurysm Repair) procedures.

Overview

EVARSim enables medical professionals and researchers to visualize and simulate stent placement along complex vessel geometries. The extension creates cylindrical stents that follow vessel centerlines.

Key Features

• Multiple Stent Support: Place up to multiple independent stents with individual parameter control
• Branch Selection: Support for branched vessel structures (e.g., inverted Y configurations)
• Real-time Parameter Adjustment: Live updates of stent radius, length, position, and resolution
• Smooth Curve Following: Advanced spline interpolation for natural stent curvature
• Professional Appearance: Rigid end caps and smooth surfaces mimicking real stents
• 3D Branch Labeling: Visual branch numbering for easy identification
• Centerline Smoothing: Conservative smoothing to reduce sharp angles while maintaining accuracy

Installation

1. Download: Clone or download this repository
2. 3D Slicer: Ensure you have 3D Slicer 5.0+ installed
3. Load Extension:
   • Open 3D Slicer
   • Go to Edit → Application Settings → Modules
   • Add the EVARSim directory to the module paths
   • Restart 3D Slicer
4. Access Module: Find "EVARSim" in the module dropdown under the "Examples" category

Usage

Basic Workflow

1. Load Centerline Data:

   • Use the "Input Model" selector to load a VTK polydata file containing vessel centerlines
   • Alternatively, use the "Centerline" selector for markup curve nodes

2. Select Output Model:

   • Choose or create an output model node where the stent will be displayed

3. Configure Stent Parameters:

   • Radius: Control stent diameter (0.1 - 10.0 units)
   • Length: Set stent length (1.0 - 200.0 units)
   • Position: Place stent along centerline (0.0 = start, 1.0 = end)
   • Resolution: Adjust surface smoothness (4-32 sides)

4. Multiple Stents (Optional):

   • Use "Number of Tubes" slider to create multiple stents
   • Select individual stents from the "Tube Selector" dropdown
   • Each stent has independent parameters

5. Branch Selection (For Branched Vessels):

   • Branched centerlines automatically show branch selector
   • Choose specific branch for each stent
   • Branch numbers are displayed in 3D view

6. Advanced Options:

   • Smoothing Factor: Apply conservative centerline smoothing (0.0 - 1.0)
   • Real-time parameter updates as you adjust sliders

File Format Requirements

Supported Input Formats:

• VTK Polydata (.vtk): Containing polyline data representing vessel centerlines
• 3D Slicer Markup Curves: Created using Slicer's markup tools

VTK Polydata Structure:

• Must contain LINES data representing centerline segments
• Points should be ordered sequentially along vessel paths
• Branched structures supported (multiple line segments)

Branch Support

For branched vessel structures (e.g., aortic bifurcations):

1. Automatic Detection: EVARSim automatically detects multiple branches in VTK files
2. Visual Labels: Branch numbers appear as yellow labels at branch endpoints
3. Individual Selection: Each stent can be assigned to a specific branch
4. Independent Control: All parameters can be set independently per stent

Tips for Best Results

• Centerline Quality: Use high-quality, properly oriented centerlines for best results
• Length Settings: For full-length stents, use length values ≥100 units
• Multiple Stents: Use different colors automatically assigned to distinguish multiple stents
• Smoothing: Start with smoothing factor 0.3, adjust based on centerline complexity
• Resolution: Higher resolution (16-32) for final visualization, lower (8-16) for real-time adjustment

Technical Details

Algorithm Overview

1. Centerline Processing:

   • Load and analyze input centerline data
   • Apply optional conservative smoothing
   • Extract specific segments based on length/position parameters

2. Control Point Reduction:

   • Reduce segment to 4 strategic control points
   • Ensures smooth curves while maintaining shape fidelity

3. Spline Interpolation:

   • Apply VTK Cardinal Spline smoothing to control points
   • Generate 20 smooth interpolated points along curve

4. Stent Generation:

   • Create cylindrical geometry using VTK TubeFilter
   • Add rigid, perpendicular end caps
   • Apply proper surface normals for smooth appearance

Dependencies

• 3D Slicer 5.0+
• VTK 9.0+ (included with Slicer)
• NumPy (included with Slicer)
• Python 3.9+ (included with Slicer)

Example Data

The extension includes CL_model.vtk - a sample branched centerline file of the aorta and the aortic bifurcation.

Troubleshooting

Common Issues:

• No stent appears: Check that input model contains valid polyline data
• Stent in wrong position: Verify centerline orientation and adjust position parameter
• Rough surface: Increase resolution parameter or check centerline quality
• Branch labels missing: Ensure VTK file contains multiple line segments for branches

Performance:

• For large datasets, start with lower resolution during adjustment
• Increase resolution for final visualization
• Multiple stents may require more processing time

Development

File Structure

EVARSim/
├── EVARSim.py              # Main module implementation
├── Resources/
│   ├── UI/EVARSim.ui      # User interface definition
│   └── Icons/EVARSim.png  # Module icon
└── CL_model.vtk           # Sample centerline data

Key Methods

• _reduceCenterlinePoints(): Strategic point reduction
• _applySplineSmoothing(): Spline interpolation
• _createTubeAlongCurve(): Stent geometry generation

License

See License.txt. This extension is developed for medical research and educational purposes. Please ensure compliance with your institution's software usage policies.

Contributing

Contributions welcome! Please ensure all changes maintain compatibility with 3D Slicer's scripted loadable module framework.

Citation

If you use EVARSim in your research, please cite appropriately and acknowledge the 3D Slicer platform.

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Version: 1.0
3D Slicer Compatibility: 5.0+
Last Updated: 2024