In vivo documentation of cutaneous inflammation using spectral imaging

Typical manifestations of cutaneous inflammation include erythema and edema. While erythema is the result of capillary dilation and local increase of oxygenated hemoglobin concentration, edema is characterized by an increase in extracellular fluid in the dermis, leading to local tissue swelling. Both of these inflammatory reactions are typically graded visually. We demonstrate the potential of spectral imaging as an objective noninvasive method for quantitative documentation of both erythema and edema. As examples of dermatological conditions that exhibit skin inflammation we applied this method on patients suffering from (1) allergic dermatitis (poison ivy rashes), (2) inflammatory acne, and (3) viral infection (herpes zoster). Spectral images are acquired in the visible and near-IR part of the spectrum. Based on a spectral decomposition algorithm, apparent concentrations maps are constructed for oxyhemoglobin, deoxyhemoglobin, melanin, optical scattering, and water. In each dermatological condition examined, the concentration maps of oxyhemoglobin and water represent quantitative visualizations of the intensity and extent of erythema and cutaneous edema, correspondingly. We demonstrate that spectral imaging can be used to quantitatively document parameters relevant to skin inflammation. Applications may include monitoring of disease progression as well as screening for efficacy of treatments.