A Simulation Study of Carbon Dot-Assisted Photothermal Heating in Tumor Tissue.

Purpose: The purpose of the study was to investigate photothermal heating and thermal damage in breast tumor tissue under laser irradiation in the presence of carbon dots acting as enhanced optical absorbers. Methods: A two-dimensional numerical model based on the transient bioheat transfer equation was developed by coupling radiative heat transfer and solved using the finite element method in COMSOL Multiphysics. The tumor region was modeled as a circular domain embedded within normal breast tissue. Thermal damage was quantified using the cumulative equivalent minutes at 43°C (CEM43) model. Parametric analysis was carried out to evaluate the effects of tumor absorption coefficient, carbon dot absorption coefficient, photothermal conversion efficiency, blood perfusion rate, and tumor depth on temperature evolution. Results: Localized heating was observed within the tumor region, with peak temperatures reaching approximately 60°C after 600s of irradiation. Temperature elevation increased with increasing optical absorption and irradiation duration, whereas blood perfusion reduced thermal accumulation. Thermal damage analysis indicated that the irreversible damage threshold (CEM43 >60 min) was achieved throughout the tumor region after 600s of irradiation, suggesting effective thermal destruction of tumor tissue, while damage to surrounding healthy tissue remained limited. Conclusions: The model demonstrates that carbon dots can effectively enhance photothermal heating in tumor tissue and achieve thermal damage. The findings provide a computational framework for optimizing laser-based tumor therapy while maintaining thermal safety.