Multilayer model of photon diffusion in skin.
A diffusion model describing the propagation of photon flux in the epidermal, dermal, and subcutaneous tissue layers of the skin is presented. Assuming that the skin is illuminated by a collimated, finite-aperture source, we develop expressions relating photon flux density within the skin and intensities re-emitted from the skin surface to the optical properties of the individual layers. Model simulations show that the rate at which re-emitted intensities diminish with radial distance away from the source can provide information about absorption and scattering in underlying tissues. Re-emitted intensities measured from homogeneous and two-layer tissue phantoms compare favorably with model predictions. We demonstrate potential applications of the model by estimating the absorption (sigma a) and transport-corrected scattering (sigma's) coefficients of dermis and subcutis from intensities measured from intact skin and by predicting the magnitude of the optical-density variations measured by a photoplethysmograph.
Schmitt
J M
JM
Division of Research Services, Biomedical Engineering and Instrumentation Branch, National Institutes of Health, Bethesda, Maryland 20892.
Zhou
G X
GX
Walker
E C
EC
Wall
R T
RT
D004058:Diffusion; D006801:Humans; D008433:Mathematics; D008954:Models, Biological; D011827:Radiation; D012867:Skin / Q000528:radiation effects*