Torso Model Generation for Simulating Pacemaker Performance

Overview

MicroPort develop lifesaving medical products for patients around the world. One of MicroPort’s specialties is in manufacturing cardiac rhythm management devices (CRM) for treating cardiac rhythm disorders and heart failures. The company use Synopsys Simpleware software to model complex pacemaker geometries to better understand patient therapies for conditions such as bradycardia and tachycardia. MicroPort typically use animal testing for their devices, but this is expensive, time-consuming, and has significant ethical risks when trying to reduce errors. Image-based finite element (FE) simulation offers an alternative testing method that reduces reliance on animal testing, cuts the risk of device failure, and provides insights without the same ethical hazards as animal testing.

Highlights:

Simulation of human body models reduces the need for animal testing
Simulation is fast, efficient, and less expensive
Use of Simpleware software allows models to be repaired for meshing
Simpleware software models provide direct route to simulation

Thanks to:

I. Rattalino (System Engineer), MicroPort CRM:

“We had the idea to simulate our medical devices in a virtual platform, but were stuck with the importation of a human body in the simulation software. Thanks to Synopsys Simpleware software, we easily solved our problem of importation, and the virtual simulation has become part of our feasibility practice today. I highly recommend Simpleware software!”

Processing a Torso Model

MicroPort began their simulation process with a realistic geometry developed from datasets available via ETH Zurich and the U.S. Food & Drug Administration. Simpleware software was used to process the original STLs and segment regions of interest for simulation. The ease-of-use of Simpleware software enabled fixes to be made to individual part triangulation errors such as holes, vertex-vertex-connections, and non-manifold edges. The processing in Simpleware software made the STL data suitable for meshing and simulation.

Processing of original geometries in Simpleware software to make simulation-ready meshes

Creating Robust FE Models

Once the image data was segmented, Simpleware software was used to export simulation-ready models: volume meshes for COMSOL Multiphysics^®, and NURBS IGES files for geometry editing and re-meshing. The Simpleware meshes are guaranteed watertight, with smooth, accurate geometries and correct topology without gaps. This level of quality makes the meshes ready for electromagnetic (EM) simulations in COMSOL Multiphysics^®.

Simpleware software used to export robust models for COMSOL Multiphysics^®

Generating Human Heart Models

To improve the detail of the simulation, Simpleware software was used to process a heart model created from a separate dataset. The main task was to add chambers to the original heart model, with image processing tools employed to remove unnecessary details from the image data. Segmentation of chambers, and the closing of the outer surface of the model to a solid allowed individual NURBS files to be exported from Simpleware software into COMSOL.

Export of NURBS heart model from Simpleware software to COMSOL

EM Simulation

The Simpleware meshes were used in COMSOL Multiphysics^® to test placement of electrodes within the body and tissue conductivity when applying voltage. The output was the current pathway and the electric field inside the heart. The simulation results were compared with the literature, and demonstrated a deviation error of between 7-20% of expected results, depending on the configuration.

Pathways of Electric field and Current Density in COMSOL Multiphysics^®

Conclusion

The FE models were suitable for comparing different device-anatomy configurations to determine which configuration is better. The model can determine the optimal position of the electrodes, and optimal pathways to maintain defibrillation at an acceptable level to both simplify the implant procedure and deliver patient comfort. Using these techniques allow MicroPort CRM to reduce their reliance on costly animal tests and improve efficiency and accuracy for their workflows.