A Multiphysics Model for Radiofrequency Activation of Soft Hydrated Tissues

Area of Science:

• Computational mechanics
• Biophysics
• Soft tissue modeling

Background:

• Understanding the electro-thermo-mechanical response of soft tissues is crucial for applications like radiofrequency ablation.
• Cellular-level mechanisms, such as water evaporation and temperature changes, significantly influence tissue behavior.
• Existing models often lack the integration of these micro-scale phenomena with macro-scale tissue response.

Purpose of the Study:

• To develop and validate a multi-physics computational model for hydrated soft tissues undergoing radiofrequency activation.
• To investigate the impact of cellular-level mechanisms, including water evaporation and temperature effects, on tissue electro-thermo-mechanical behavior.
• To incorporate a robust method for modeling tissue damage evolution consistent with thermodynamic principles.

Main Methods:

• A micromechanical model was developed to derive an equation of state (EOS) accounting for water evaporation and temperature effects.
• A continuum-level thermo-mechanical model was coupled with the EOS to simulate tissue response.
• A level set method, derived from the second law of thermodynamics and Griffith's fracture criterion, was employed to track tissue damage.
• Simultaneous solution of discretized equations using a GMRES iterative solver with block preconditioning for efficient computation.

Main Results:

• The model accurately captures the electro-thermo-mechanical response of soft tissues under radiofrequency activation.
• The integration of cellular mechanisms, particularly water evaporation and temperature, was shown to be critical.
• The level set method effectively simulated interfacial tissue damage evolution.
• Computational efficiency and accuracy were demonstrated through example problems and experimental validation.

Conclusions:

• The developed multi-physics model provides a comprehensive framework for simulating radiofrequency-induced effects in soft tissues.
• The approach effectively links micro-scale cellular processes to macro-scale tissue deformation and damage.
• The validated computational technique offers a powerful tool for research and clinical applications involving radiofrequency therapies.