Validity of the semi-infinite tumor model in tissue optics: A Monte Carlo study

A Monte Carlo code based on a public domain code, MCML, was developed for the simulation of light transport in layered tissue models with buried tumor-like targets. We used the code to investigate the validity of the semi-infinite tumor assumption in an epithelial tissue model. The epithelial tissue model consists of three layers, which includes the top epithelium, the middle tumor and the bottom stroma. Diffuse reflectance is simulated for a fiber-optic probe in commonly used configurations. It is demonstrated that the validity of the semifinite tumor layer model depends on the fiber-optic probe configuration and the tumor dimensions. The results of this study provide a guide in the selection of appropriate light transport models and fiber-optic probe configurations in the optical diagnosis of early epithelial cancers.