Direct and Doppler angle-independent measurement of blood flow velocity in small-diameter vessels using ultrasound microbubbles.

This article represents an initial attempt to demonstrate the feasibility of a novel method for measuring flow velocity in small vessels, which is a direct, noninvasive, ultrasound-guided, and Doppler angle-independent method. In vitro, experiments were designed to mimic blood flow inside tubes. Harmonic ultrasound imaging was used to track the movement of microbubbles, and the mean flow velocity was calculated. In vivo, the flow velocities were measured in the central arteries of rabbit ears. This method can be used whenever the Doppler ultrasound cannot measure the velocity in small vessels because of either low sensitivity or Doppler angle limitation.