[Ultrasound angiography: phantom measurements of slow blood flow]

Power Doppler ultrasound is a color-coded Doppler ultrasound method based on the strength of the Doppler shift signal. The sensitivity for slow flow was tested with different flow phantoms. The lowest detectable velocity was 0.04 cm/s in a water- or oil-filled tank at an angle of 45 degrees and 0.24 cm/s in an oil medium at an angle of 86 degrees. The pulse repetition frequency (PRF) was 100 kHz at the lowest detectable velocities, the acquisition time depended mostly on the attenuation of the medium. The new method depended very little on the angle of insonation. Under ideal conditions detectable flow velocities are within the range of mean capillary flow velocity.