Thermal damage analysis of sub-surface soft tissue sarcoma for indocyanine green mediated photothermal cancer therapy

Abstract

Photothermal therapy is a minimal invasive technique to treat tumors situated near the skin or other light accessible organs. Here, a photothermal agent is delivered to tumor either intratumorally or intravenously and the tumor is irradiated with near infrared (NIR) radiation to generate heat for thermal damage of tumor. In this paper, thermal damage of soft tissue sarcoma, a type of sub-surface forearm tumor, is evaluated for photothermal therapy using numerical simulations. Indocyanine green (ICG) is used as photothermal agent and the effect of various spatial distributions and doses of ICG for sub surface tumors located at various depths (3–6 mm) were investigated. Further, numerical simulation is validated experimentally through tumor-tissue mimicking phantoms. Computations were performed in MATLAB software using Lattice Boltzmann method and validated through experiments using tumor-tissue mimicking phantoms. Results show that the thermal damage region (damage parameter (Ω) of magnitude 4.6) was enlarged on increasing the concentration of ICG while it got shrunk for the deeper tumors. Computations reveal that ICG concentration of 50 μg/mL is optimum, for intravenous distribution, for photothermal therapy with minimal damage to surrounding tissue. It is found that irradiation duration of more than 900 s is required to achieve the complete damage of tumor. For the case of deeper tumors, about 1200 s of exposure is required, at irradiation intensity of 0.25 W/cm2. This study provides a numerical approach to determine therapeutic parameters and demonstrates the thermal damage for subsurface tumors through ICG mediated photothermal therapy by proper selection of therapeutic parameters.