Cyclic and radial variation of the echogenicity from human carotid artery and porcine blood

The cyclic and radial variation of the echogenicity from human blood and porcine blood was investigated using a linear M12L transducer with a GE LOGIQ 700 Expert system. The bright collapsing ring phenomenon, a bright echogenic ring converging from the periphery to the center of the tube wall and eventually collapsing during a pulsatile cycle from the cross‐sectional B mode images, was observed from porcine blood in a mock flow loop with a diameter of 0.95 cm at certain flow conditions. The bright ring phenomenon from porcine blood was stronger as the peak speed increased from 19 to 40 cm/s while the mean echogenicity decreased. As the stroke rate increased from 20 to 60 beats/minute, the phenomenon was weaker. As the hematocrit increased from 12 to 45%, the phenomenon became obvious. The black hole phenomenon was also observed at certain flow conditions. The well‐known nonlinear hematocrit dependence on echogenicity was observed near the wall but the dependence pattern was changed at the center of the tube. The similar bright ring phenomenon was also observed at the harmonic images in vivo on 10 human carotid arteries. Aggregation due to the shear rate and acceleration is thought to be the explanation of the phenomena.