Mechanisms of Laser-Tissue Interaction: I. Optical Properties of Tissue

Today, lasers are widely used in biology and medicine, and the majority of health centers and hospitals utilize modern laser systems for diagnosis and therapy applications. Researchers have introduced different medical applications for different lasers used in surgeries and other medical treatments. Medical lasers can be categorized in both diagnosis and therapy branches. Main difference between diagnosis and therapy applications is the type of laser-tissue interactions. In diagnosis, one tries to arrange a noninvasive method to study the normal behavior of tissue without any damage or clear effect on tissue. But in therapy, such as surgery, a surgeon uses laser as a knife or for affecting a specific region. So, the medical laser applications are defined by the interaction type between laser light and tissues. The knowledge of laser-tissue interaction can help doctors or surgeons to select the optimal laser systems and modify the type of their therapy. Therefore, we seek to review the mechanisms of laser- tissue interaction. In this paper, the optical properties of biological tissue such as absorption, scattering, penetration and fluorescence are reviewed. Also, the effects of these properties on laser penetration in tissue have been explained.