Noninvasive quantitative assessment of diabetic wounds with diffuse photon density wave technology

Abstract

Quantitative non-invasive assessment of the wound healing process in chronic wounds may assist in selection and monitoring of expensive treatments. The Diffuse Photon Density Wave (DPDW) methodology at near infrared wavelengths can be used to non-invasively measure the optical absorption and reduced scattering coefficients of tissue at depths of several millimeters. Changes in the optical properties of tissue at near-infrared wavelengths (685nm-950nm) are caused by changes in blood volume, oxygenation, and tissue hydration. A four-wavelength DPDW system with a single source position and four detectors was used to monitor the optical properties of wounds in healthy and streptozotocin-induced diabetic rats. Optical data obtained after inflicting full-thickness wounds on the dorsal region of diabetic and control rats indicate that DPDW technology can be used to monitor wound healing and differentiate the rate of impaired vs. normal wound healing. The concentrations of oxyhemoglobin, deoxyhemoglobin and water were calculated from the optical absorption coefficients. Changes in hemoglobin concentration may indicate increased vascularization throughout the wound healing process, while changes in water content may reflect inflammation following tissue injury. These physiological changes are supported by qualitative immunohistochemical analysis of wound biopsies.