Patent ID: 6196973
Filing Date: 2001-03-06
Classification: A61B

Abstract:
A method for determining blood flow velocity in a blood vessel of a patient, comprising the following steps:introducing a contrast agent into the blood vessel upstream from a modulation point, the contrast agent comprising a liquid carrier containing a concentration of ultrasound reflectors;focusing a beam of ultrasound from a transducer onto the modulation point, the transducer having a high state, in which the ultrasonic beam significantly changes the ultrasound reflectivity of the insonified reflectors, and a low state, in which the reflectors pass the modulation point substantially unchanged;energizing the transducer alternately between the high and low states according to a predetermined modulation sequence, thereby creating a pattern of a plurality of contrast agent gaps in which the reflectivity of the reflectors is changed;from a sensing point in the blood vessel that is downstream from the modulation point, sensing an ultrasonic echo signal; anddetermining a transit time of the contrast agent, and thus the blood flow velocity, between the modulation and sensing points, by calculating a time shift function of at least a portion of the modulation sequence and a corresponding portion of the echo signal.