METHOD OF AND APPARATUS FOR ECHOGRAPHIC DETERMINATION OF THE VISCOSITY AND THE PRESSURE GRADIENT IN A BLOOD VESSEL

This invention includes a method of determining the viscosity and the pressure gradient in a blood vessel, including the acquisition of n.gtoreq.2 blood speed values, corresponding to the same number of n radii of the blood vessel, determined along a diameter situated in a given axial position, formation of a blood speed vector by means of said n blood speed values, and evaluation of said viscosity and pressure gradient on the basis of a transformation of said blood speed value, including formation of a linear relation which directly links a flow rate vector (y) to the speed derivative vector (h), factorized by the viscosity (.mu.), and to the pressure gradient vector (.sigma.), and simultaneous evaluation of the two values to be determined for the viscosity (.mu.) and the pressure gradient (.sigma.) on the basis of said direct equation. The velocities are advantageously determined by correlation of ultrasonic signals supplied by an echography apparatus. This invention also includes apparatus for the practice of this method.