Ultrasonic visualization of dynamic behavior of red blood cells in flowing blood

Abstract

It is well known that the scatter of ultrasound by blood is mainly attributed to red blood cells (RBCs) and RBC aggregation. In the present review, researches of hemodynamic influence on RBC aggregation and ultrasound backscatter from blood were overviewed. A mock flow loop and a cylindrical chamber were employed to produce various blood flows, such as pulsatile, oscillatory, and rotational flow. The "black hole" (BLH), a dark hole at the tube center surrounded by bright zone in the cross sectional B-mode image and "bright collapsing ring" (BRCR) phenomena, appearance of bright ring at the periphery and collapse of it at the center during a pulsatile cycle, were observed under pulsatile flow. The combined effects of shear rate and flow acceleration on RBC aggregation were suggested as a possible mechanism for these phenomena. The stroke volume-dependence of the "bright ring" phenomenon under oscillatory flow could also be explained by flow acceleration. The enveloped echo images from rotational flow in a compact blood chamber showed the spatial and temporal variations of RBC aggregation, which varied with the mammalian species. In the stenotic model, it was found that the echogenic variation increased locally at a distance of three tube diameters downstream from the stenosis during decelerating period, which was proposed to be mainly due to flow turbulence. The similar 'bright ring' was also observed from in vivo human carotid artery in harmonic imaging.

Velocity field measurements of valvular blood flow in a human superficial vein using high-frequency ultrasound speckle image velocimetry

“…Due to the formation of RBC aggregates, ultrasound backscatter is enhanced, and bright speckles appear in the B-mode images captured at the frequency range of clinical ultrasound imagers [20][21][22]. As the frequency of ultrasound scanner increases, smallsized RBC aggregates or even RBCs can be detected in B-mode images [15]; this is because the ultrasound backscatter from RBCs is proportional to the fourth power of the incident frequency based on the Rayleigh scattering theory.…”

Microfluidic-based speckle analysis for sensitive measurement of erythrocyte aggregation: A comparison of four methods for detection of elevated erythrocyte aggregation in diabetic rat blood

“…The extent of erythrocyte aggregation (EA) is mainly affected by force balance; an aggregating force induced by the presence of macromolecules, and disaggregating forces including the negative surface charge and shear force developed in blood flows. 3 This phenomenon is of interest in hemorheology, because the shear dependence of viscosity is mainly attributed to EA. Specifically, large rouleaux formations under low shear a) E-mail: sjlee@postech.ac.kr.…”