title: Temperature modulation of the visible and near infrared absorption and scattering coefficients of human skin.
abstract: We determine temperature effect on the absorption and reduced scattering coefficients (mu(a) and mu(s)(')) of human forearm skin. Optical and thermal simulation data suggest that mu( a) and mu(s)(') are determined within a temperature-controlled depth of approximately 2 mm. Cutaneous mu(s)(') change linearly with temperature. Change in mu(a) was complex and irreversible above body normal temperatures. Light penetration depth (delta) in skin increased on cooling, with considerable person-to-person variations. We attribute the effect of temperature on mu(s)(') to change in refractive index mismatch, and its effect on mu(a) to perfusion changes. The reversible temperature effect on mu (s)(' ) was maintained during more than 90 min. contact between skin and the measuring probe, where temperature was modulated between 38 and 22 degrees C for multiple cycles While temperature modulated mu(s)(' ) instantaneously and reversibly, mu(a) exhibited slower response time and consistent drift. There was a statistically significant upward drift in mu(a) and a mostly downward drift in mu( s)(') over the contact period. The drift in temperature-induced fractional change in mu(s)(') was less statistically significant than the drift in mu(s)('). Deltamu( s)(') values determined under temperature modulation conditions may have less nonspecific drift than mu(s)(') which may have significance for noninvasive determination of analytes in human tissue.
authors.affiliation: Abbott Laboratories, Diagnostics Division, 100 Abbott Park Rd, Abbott Park, Illinois 60064, USA. omar.khalil@abbott.com
authors.forename: Omar S
authors.initials: OS
authors.lastname: Khalil
authors.forename: Shu-Jen
authors.initials: SJ
authors.lastname: Yeh
authors.forename: Michael G
authors.initials: MG
authors.lastname: Lowery
authors.forename: Xiaomao
authors.initials: X
authors.lastname: Wu
authors.forename: Charles F
authors.initials: CF
authors.lastname: Hanna
authors.forename: Stanislaw
authors.initials: S
authors.lastname: Kantor
authors.forename: Tzyy-Wen
authors.initials: TW
authors.lastname: Jeng
authors.forename: Johannes S
authors.initials: JS
authors.lastname: Kanger
authors.forename: Rene A
authors.initials: RA
authors.lastname: Bolt
authors.forename: Frits F
authors.initials: FF
authors.lastname: de Mul
mesh_terms: D000042:Absorption; D003198:Computer Simulation; D004307:Dose-Response Relationship, Radiation; D005542:Forearm / Q000473:pathology / Q000502:physiology / Q000528:radiation effects; D006358:Hot Temperature; D006801:Humans; D007259:Infrared Rays; D008027:Light; D008954:Models, Biological; D019047:Phantoms, Imaging; D012542:Scattering, Radiation; D012867:Skin / Q000166:cytology / Q000528:radiation effects*; D012879:Skin Physiological Phenomena / Q000528:radiation effects*; D012881:Skin Temperature / Q000502:physiology / Q000528:radiation effects; D013696:Temperature; D041622:Tomography, Optical / Q000379:methods*