Simulation of heat distribution and thermal damage patterns of pulse laser for uterus using finite element analysis

Photoacoustic imaging is a promising technique that complements ultrasound and is able to distinguish benign from malignant tumors. Higher laser energy results in higher signal-to-noise ratio. Unfortunately, the higher laser energy is more costly and the maximum laser energy is also limited by the maximum permissible exposure imposed by the American National Standards Institute for human skin. The study of interaction of laser with tumorembedded uterine tissue is of great theoretical and practical significance for the laser diagnosis and treatment of endometrial cancer in medicine. In this paper, a 2D tumor-embedded uterine model, which was established by the histological structure of uterus, has been developed incorporating light propagation and heat transfer in soft tissues using a commercial FE simulation package, COMSOL Multiphysics. The light propagation were implemented through the tissues using the diffusion equation. Bioheat transfer in tissues was simulated using Pennes equation for temperature change, and the damage of the tissues was simulated by employing Arrhenius equation. The simulation results show that a cylindrical diffuser can illuminate almost the whole uterus at the same time. The light absorptions of the tumor and the normal tissue are big difference which could result in a high signal-to-noise ratio. Furthermore, the damage of the left side of the tumor is getting worse and irreversible after the laser irradiation. The conclusions are helpful to optimize the laser source and to improve the imaging depth in a photoacoustic imaging system, providing some significance for the further study of the early diagnosis of endometrial cancer.