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

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

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.

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

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

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

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

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

Results

Results

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

Results – Video 2

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

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

Stent Video

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

Acknowledgements – Team – Xunlei Wu Vincent Luboz Julien Lenoir Christian Duriez Paul Neumann Stephane Cotin – Funding – TATRC CIMIT