Feasibility Study of High-Frequency Ultrasonic Blood Imaging in Human Radial Artery

The present study investigates cyclic variation in blood echogenicity (CVBE) in vivo using high-frequency ultrasound (HFUS). Blood echogenicity (BE) and vessel diameter (VD) were obtained from cross-sectional B-mode images of the radial artery of six volunteers (three young and three old volunteers) acquired at a frequency of 20 MHz. The magnitudes of the cyclic variations in BE and VD were 0.83 ± 0.18 dB and 0.29 ± 0.05 mm, respectively. CVBE was observed to be out of phase with the cyclic variation in VD, which is known to be in phase with blood flow velocity. This result is different from those in previous studies, which were performed in the carotid artery at lower frequencies. In addition, the magnitude of CVBE in the older group (0.96 ± 0.05 dB) was higher than that in the younger group (0.63 ± 0.06 dB, p < 0.005), whereas the magnitude of variation in VD was not significantly different between the two groups (p = 0.119). This feasibility study suggests that HFUS B-mode blood imaging of human small vessels is useful for the noninvasive measurement or monitoring of the dynamic variation of hemorheological properties in human blood.