title: Noninvasive assessment of microcirculation of living organs and tissues using laser.
abstract: For studying microcirculation of intact tissues or organs, a new noninvasive, heat-transient method using laser photoexcitation is described. As a heating source an argon ion laser or R6G dye laser was used via a quartz fiber optic guide. Infrared radiation from heated tissue was detected by a thermography apparatus. After switching the laser irradiation on and off, a thermal transient curve of a model tissue, the skin, was biphasic: a component with a fast time constant and the other with a slow time constant. The temperature increases of both phases following laser irradiation were linear to the applied power from the laser onto the tissue. The temperature rises as a function of the wavelength of irradiated light have shown that the absorption of the light by tissue hemoglobin is a main heat-generation source. Furthermore, the temperature rises as a function of tissue blood volume and flow have shown that the component with a slow time constant is more related to the tissue hemoglobin concentration and tissue blood flow and heat conductivity. Thus, the analysis of heat-transient curves following laser irradiation gives information as to regional tissue blood volume, blood flow, and tissue heat conductivity.
mesh_terms: D000818:Animals; D001810:Blood Volume / Q000528:radiation effects; D007834:Lasers; D008297:Male; D008722:Methods; D008833:Microcirculation / Q000528:radiation effects; D051381:Rats; D012881:Skin Temperature / Q000528:radiation effects