Simulation-Based Treatment Protocol Design for Damaging Breast Tumor Using Laser Photothermal Therapy

Abstract

Laser photothermal therapy utilizes gold nanorods/nanoshells embedded in tumors to enhance laser energy absorption in tumors via minimizing laser absorption in superficial tissue regions. The objective of this study is to develop a theoretical model to determine temperature elevations in a 10 mm diameter spherical tumor embedded inside a human breast model and to design a treatment protocol using laser photothermal therapy. Using the Pennes bioheat equation, we simulate temperature fields inside the tumor and its surrounding tissue before and during laser heating. Theoretical simulations show that using a laser intensity of 24000 W/m² at the skin surface with a laser spot of 10 mm in diameter, the maximal and minimal temperatures in the tumor are 65 ℃ and 47 ℃, respectively. Equivalent minutes at 43 ℃ (EM₄₃) are used to assess accumulated thermal damage within the tissue during the heating. Results illustrate that the heating time for causing irreversible thermal damage to the entire tumor is 916 s using the selected laser intensity and spot size. Although cold-water droplets are sprayed at the skin surface to protect skin and its surrounding healthy tissue, it is found that collateral thermal damage to the healthy tissue near the tumor (up to 2 mm) is inevitable. We conclude that theoretical simulation is a useful tool to evaluate temperature field during laser photothermal therapy and to design effective and safe heating protocols in clinical applications.