Thermodynamic technique for the quantification of regional blood flow

A method is described to quantify regional blood flow by thermal analysis. A weak temperature field is established in a tissue and for a thermal steady state, unidirectional heat flux and the associated temperature gradient are measured simultaneously across a small fixed segment of the tissue. This information is evaluated with probe calibrations for homogeneous isotropic fluids, with data from ancillary measurements in the nonperfused tissue and with values of specific heat and density of blood to express local blood flow in heat transfer [effective thermal conductivity (W. degrees C-1 . cm-1 x 10(-3) and/or in perfusion (ml . min-1 . cm-3)] terms. The technique measures local perfusion in small tissue volumes and is usable in acute or chronic experiments. Its accuracy is not a function of the absolute steady-state temperature of the tissue or of its metabolic heat production.