Patent ID: 7251518

Claim:
A method for the non-invasive measurement of the concentration of blood constituents in central blood vessels, particularly the hemoglobin concentration or oxygenation of the blood, by measuring backscattered light under the action of ultrasonic radiation, the method comprising: (a) focusing the ultrasonic radiation on an interior of a central blood vessel; (b) presetting a fixed pulse length and repetition time for the ultrasonic radiation; (c) arranging a light source and an adjacent detection unit for detecting the backscattered light on a skin surface over the blood vessel in such a way that a spacing between the light source and a plurality of light receptors of the detection unit correspond to a depth of the examined blood vessel; (d) illuminating a target tissue with at least two discrete light wavelengths; (e) measuring the backscattered light intensity in integrating manner over a surface of the detector and a plurality of ultrasonic pulses; (f) determining an average light intensity distribution over a duration of a pulse; (g) eliminating time-constant components and carrying out a Fourier transformation of time to frequency coordinates; (h) drawing conclusions concerning a blood flow rate and its backscattering power for each of the at least two light wavelengths while determining the blood vessel depth; (i) drawing conclusions concerning the quantity of the blood constituents contributing to a signal from the determined backscattering power; and (j) calculating concentrations of the blood constituents in the blood vessel while taking account of an ultrasonic focus volume contributing to the signal and the blood flow rate.