High frequency B-mode ultrasound blood flow estimation in the microvasculature

High frequency ultrasound imaging has shown great ability in various applications for visualization of the microcirculation. A new speckle-variance flow processing (SFP) algorithm has been developed for noninvasive estimation of slow blood flow. This technique is based on analyzing the changes of B-mode image intensity along sequences of images. The method has been evaluated on a flow phantom with blood-mimicking fluid in the velocity range from 0.1 mm/s to 30 mm/s. The velocity index estimated with the SFP method shows a linear increase as a function of calibrated flow velocity in the range of 0.1 mm/s to 1.5 mm/s. For larger flow velocities, the SFP index acts as a motion detector. Results have been compared with speckle tracking (ST) flow velocity estimation and give good agreement. Ultrasound image sequences have been processed with the proposed method. This demonstrates the feasibility of mapping slow blood flow in real time with a non-Doppler method.