Near Infrared Light Penetration in Human Tissue: An Analysis of Tissue Structure and Heterogeneities
Date of Award
Master of Science (MS)
Low level laser irradiation (LLLI) has been a controversial method of therapy due to a limited understanding of the underlying mechanisms that could cause the irradiation to provide its proposed benefits – increased blood flow, vasodilation, cell attachment, and wound healing. Near infrared (NIR) light appears able to function with nitrates and enzymes around the electric transport chain to allow biologically available nitric oxide to be released from hemoglobin and myoglobin. Nitric oxide has been shown to be a part of a mechanism that promotes blood flow, vasodilation, and wound healing.NIR penetration in biological tissue is not well described due to patient variability, site variability, and heterogeneities within tissue itself. To determine whether generalities and normative statements about NIR penetration depth can be described such that future therapies can be prescribed, many Monte Carlo simulations were run on isolated tissues, simplified tissue structures, and simulated human sites. NIR penetration is best suited for biological sites with a thin epidermis, minimal vascular tissue, and a high fat-to-muscle ratio such as the thigh, upper arm, and chest. Under these conditions it appears likely that NIR will penetrate depths of several centimeters.