Model-based simulations of pulsed laser ablation using an embedded finite element method.

Area of Science:

• Computational modeling
• Biomedical engineering
• Laser physics

Background:

• Kidney stone treatment often involves laser lithotripsy.
• Accurate modeling of thermal ablation is crucial for optimizing laser lithotripsy procedures.
• Existing models may not fully capture the complexities of pulsed laser-material interactions.

Purpose of the Study:

• To develop and validate a computational model for thermal ablation in multi-pulsed laser lithotripsy.
• To simulate the interaction of high-power lasers with kidney stone phantom materials.
• To explain experimental observations of laser ablation phenomena.

Main Methods:

• A one-sided Stefan-Signorini model for thermal ablation was employed.
• A level-set function represented the moving solid-gas interface.
• An embedded finite element method with Nitsche's method and bound constraints was used for discretization.
• The model was calibrated and validated against experimental data from BegoStone samples.

Main Results:

• The model successfully simulated pulsed laser ablation of kidney stone phantoms.
• Calibration involved adjusting surface absorption of laser energy.
• Validation confirmed the model's ability to predict crater dimensions and geometry.
• Observed trends were explained by laser beam spreading and reduced irradiance on the crater surface.

Conclusions:

• The developed thermal ablation model provides a robust framework for simulating laser lithotripsy.
• The model accurately captures the effects of laser parameters on ablation outcomes.
• Understanding laser beam dynamics is key to interpreting and predicting ablation behavior.