Perturbative diffusion theory formalism for interpreting temporal light intensity changes during laser interstitial...

Area of Science:

• Biomedical Optics
• Medical Physics
• Laser Medicine

Background:

• Laser interstitial thermal therapy (LITT) uses lasers to create thermal coagulation for therapeutic purposes.
• Monitoring treatment-induced optical changes during LITT is essential for real-time feedback and efficacy.
• Previous studies reported complex optical intensity variations during LITT, requiring further explanation.

Purpose of the Study:

• To develop a model explaining dynamic optical changes during LITT.
• To correlate interstitial light intensity variations with thermal coagulation extent and location.
• To clarify the reasons behind observed early increases in optical intensity during laser heating.

Main Methods:

• Utilized the perturbative solution of the diffusion equation for heterogeneous media.
• Formulated scattering weight functions for cylindrical line sources.
• Performed experimental measurements using ex vivo bovine liver tissue.

Main Results:

• The model explicitly links changes in detected interstitial light intensity to thermal coagulation.
• The analysis clarifies previously observed increases in optical intensity during early laser heating.
• Experimental data validated the model's predictions.

Conclusions:

• This work enhances the understanding of optical signal dynamics during LITT.
• Interstitial optical monitoring shows sensitivity and potential for tracking thermal damage.
• The developed model provides a framework for interpreting optical feedback during LITT procedures.