Methods for measuring changes in optical properties of wound tissue and correlating near infrared absorption(fNIR) and diffuse refelectance spectroscopy scattering (DRS) with tissue neovascularization and collagen concetration to determine whether wound is healing

Abstract

Optical changes of tissue during wound healing measured by Near Infrared and Diffuse Reflectance Spectroscopy are shown to correlate with histologic changes. Near Infrared absorption coefficient correlated with blood vessel in-growth over time, while Diffuse Reflectance Spectroscopy (DRS) data correlated with collagen concentration. Changes of optical properties of wound tissue at greater depths are also quantified by Diffuse Photon Density Wave (DPDW) methodology at near infrared wavelengths. The diffusion equation for semi-infinite media is used to calculate the absorption and scattering coefficients based on measurements of phase and amplitude with a frequency domain or time domain device. An increase in the absorption and scattering coefficients and a decrease in blood saturation of the wounds compared to the non wounded sites was observed. The changes correlated with the healing stage of the wound. The methodologies used to collect information regarding the healing state of a wound may be used to clinically assess the efficacy of wound healing agents in a patient (e.g., a diabetic) and as a non-invasive method

1 - 16 . (canceled) 
     
     
         17 . A system for determining if a wound in a human patient is healing, comprising:
 A light source for illuminating the wound tissue in the patient;   A diffuse photon density wave (DPDW) device that is a continuous wave, a frequency domain, or a time domain measurement device for measuring one or both of the amplitude and phase shift of the light as it propagates through the wound tissue;   calculating optical absorption coefficients using the measured amplitude or phase shift of the light;   the system providing the concentration of the oxygenated hemoglobin or the total hemoglobin in the wound tissue from the optical absorption coefficients; and the rate of change of the oxygenated hemoglobin or total hemoglobin concentration over the period of time,   thereby allowing a determination of whether there is a negative rate of change of either the oxygenated hemoglobin or total hemoglobin, indicating the wound is healing, or whether there is a negligible or positive rate of change indicating the wound is not healing.   
     
     
         18 . The system of  claim 17 , wherein the light has a wavelength between 650 and 870 nm. 
     
     
         19 . The system of  claim 17 , wherein the near infrared wavelength is selected from the group consisting of 685 nm light, 780 nm light, 830 nm light, and 950 nm light. 
     
     
         20 . The system of  claim 17 , wherein the wound is selected from the group consisting of pressure ulcers, diabetic foot ulcers, ubiquitous ulcers, and venous ulcers. 
     
     
         21 . The system of  claim 17 , further comprising differentiating a healing wound from a non-healing wound using the rate of change of total hemoglobin concentration over the period of time. 
     
     
         22 . The system of  claim 17 , wherein the measurements are taken from at least 2 mm below the surface of the wound. 
     
     
         23 . The system of  claim 17 , comprising determining the statistical variability of the measurements, wherein a higher degree of statistical variability between consecutive measurements relative to the variability in a healing wound indicates a non-healing wound. 
     
     
         24 . The system of  claim 17 , wherein the period of time is less than five weeks. 
     
     
         25 . The system of  claim 17 , wherein the concentration is measured up to five times over the period of time. 
     
     
         26 . The system of  claim 17 , wherein the threshold between the negative rate of change and the negligible rate of change is a change of −0.003 cm −1 /wk in the optical absorption coefficient.