Infrared Transmission Characteristics and Laser Tissue Interaction of Albino Pigskin Using Pulsed NIR Laser Light

This work explores near infrared transmission through albino pigskin and determines controllable factors that influence transmission efficiency. Pigskin samples of varying thicknesses were irradiated using a 1440？nm near-infrared laser diode, where a photodetector was used to measure the transmitted power, and a two-dimensional real time surface temperature distribution was recorded using infrared thermography. Results demonstrate that this technique could potentially lead to a noninvasive approach for enhancing wound healing. 1. Introduction In the last several decades, the study of electromagnetic irradiation and its influence on live tissue cells have been of great interest. Studies of laser-tissue interactions have expanded the application of photonics into the field of medicine [1]. The motivation for this particular study is to determine the parameters that influence transmission efficiency of laser-irradiated tissue, which provides photonic energy to cells for biostimulation [2]. The human skin, which comprises of three different regions: the outer layer—epidermis, the middle layer—dermis, and the inner layer—hypodermis varies both in thickness and light transmission characteristics [3]. As such, there is skepticism that laser transmission through skin can serve as a feasible approach for wound healing. Numerous approaches to wound healing have been previously explored and most have not provided control over the entire healing process. Photonic biostimulation, however, is an interesting approach to wound healing that has not been thoroughly explored. The key advantage of a photonics-based approach is reduced exposure of internal wounds to atmosphere, where the exposure to microorganisms is minimized. Ultraviolet, visible, or infrared wavelengths are candidates for photonic biostimulation; however, due to the absorption of ultraviolet and visible light on skin, these are not ideal for photonic biostimulation [4]. In contrast, infrared radiation has longer wavelength enabling it to penetrate further into the skin to reach targeted tissue and provide the needed excitation at the cellular level without cell damage [5]. When a molecule interacts with infrared light, there is a transfer of photon energy and momentum. The absorption characteristics of cellular organelles are the basis for wound healing via photonic stimulation [6]. A number of factors influence photon transmission: skin thickness, wavelength of incident beam, skin moisture content, dispersion, scattering, and absorption. The absorption can be approximated using Beer-Lamberts law: where