Physically-based models for Catheter, Guidewire and Stent simulation

1. Physically-based models for Catheter, Guidewire and Stent simulation Julien Lenoir Stephane Cotin, Christian Duriez and Paul Neumann The SIM Group – CIMIT, MGH, Harvard Medical School

2. Interventional Radiology Providing therapy through the human vascular system to prevent stroke.

3. Interventional Devices Primary Devices: guidewire and catheter Attributes: Flexible, smooth, uncompressible Manipulate: Insert/retract and twist externally Navigation: curved tip for vessel junctions Our Goal: To replicate these devices within a simulator to aid in training.

4. Challenge Thin Stiff Structures Nested Devices Multiple Contacts and Sliding conditions Large Deformations Requires High Fidelity for Radiologists

5. Previous Work • General one-dimensional models • Dynamic spline [Lenoir et al 02, Nocent & Remion 01] • Static Cosserat model [Pai 02] • Specific catheter simulation • Rigid bodies and joints (multi-body dynamics) [Dawson et al 00] • Linear elastic FEM [Nowinski 01] • Incremental FEM model [Cotin et al 05]

6. Physics-based Representation • Base Model • 6 Degrees of Freedom (translation + rotation) • Linear elasticity • Optimization • Incremental FEM for geometric nonlinearity • Performanceimprovement through sub-structure analysis

7. Collision Detection • Accomplished through optimized vascular model • Oriented graph • Each beam node of a device is tracked using • Proximity measure • Temporal coherence • Surface Partitioned • return active section • test local triangle subset Anatomical model is described in another paper on pp 273-278.

8. Collision Response • Collision response needs to account for multiple contacts and sliding conditions • Quadratic Programming proved to be too time consuming • Our Approach: Iterative Gauss Seidel • Use penalty method locally • Propagate change to other nodes • Iterate checking other nodes until no violations

9. Results

10. Results

11. Co-axial Catheter/Guidewire • One unified device rather than two • Modulate material properties based on regions: • Overlapping • Guidewire only • Catheter only • Locally update material properties using Halpin-Tsai equations.

12. Results – Video 2

13. Stents • Thin cylindrical metallic mesh • Implanted to open partially blocked vessels restoring blood flow • Expands radially when released

14. Surface Elements Beam nodes Stents • Modeling Issues: • Connect an additional surface to ‘core’ beam model • Surface constrained and expands when released • Perform collision test on surface elements • Coupled relationship between surface and beam nodes • Forces on surface elements propagated to beam nodes • Currently working on local vessel deformation

15. Stent Video

16. Conclusions and Ongoing Work • Conclusions • Real-time robust physics-based representation for wire-like devices • Defined composite technique of nested devices • Demonstrated extensions: stents • Ongoing work • Local and global deformation of anatomical model • Develop angioplasty balloon using similar principles • Investigatingcoils • Finalize complete simulation system

17. Acknowledgements – Team – Xunlei Wu Vincent LubozJulien LenoirChristian DuriezPaul NeumannStephane Cotin – Funding – TATRCCIMIT http://thesimgroup.org/