In the paper, measurement techniques to obtain the velocity field of blood flow in microcirculation in arterioles, capillaries and venules, whose diameters are less than 100 μm, are described. This review summarizes in vivo and in vitro measurement techniques for velocity and deformation of red blood cell, and also velocity of plasma.

View full abstract

An aneurysm is a vascular disease characterized by local ballooning of an arterial wall. The etiology of aneurysm formation is thought to be due to remodeling of blood vessel wall in response to hemodynamics. Changes in vessel geometry and mechanical properties of blood vessel wall induce alteration in the pattern of hemodynamics which then provides new mechanical stimuli to the vessel wall to cause further wall remodeling. We carried out a computer simulation of the geometric change in the aorta with considering the interaction between hemodynamics and aortic wall to see how the aortic geometry changes when mechanical properties change and the wall grows in response to hemodynamics. A mechanical behavior of an aortic wall is depicted as a combination of continuum model and discrete elements model. The influence of hemodynamics on the wall is expressed by a remodeling model that alters mechanical properties and provides growth of the wall based on wall shear stress (WSS). Remodeling of the aortic wall is expressed by altering mechanical properties and providing wall growth. The results demonstrated formation of the fusiform aneurysm at the proximal side of the aortic arch.

View full abstract

Erythrocyte is the major cellular component in human blood. Its deformability affects the hemo-dynamical performance in microcirculation. So measurement and evaluation of its deformability is really important to understand and diagnose microangiopathy. The author tried to evaluate the deformability of each erythrocyte by measuring the time constant of shape recovery just after the erythrocyte left the micro-channels under the micro visualization. The artificially stiffer the cell membrane and thinner hemoglobin solution was using glutaraldehyde and hypotonic saline solution, the shorter the time constant for relaxation became compared to healthy erythrocytes.. And the time constant distribution of each donor showed the lognormal distribution. These result indicates that the shape recovery process is able to be modeled by the Kelvin model and the deformability of individual erythrocytes can be quantitated by the time constant for relaxation measured by this techniques. Finally, this paper introduce the relationship between the time constant and blood test results of various diabetic subject.

View full abstract

Rolling of neutrophils on the endothelium of post-capillary venules is the first step in their immune response. Parameters which affect rolling characteristics of the neutrophils are attachment/detachment of adhesive molecules, surface morphology of the endothelium and contact force of the neutrophils on the endothelium applied from axially accumulated erythrocytes. In most former research studies on rolling, however, the contact force has been ignored. In this study, an inclined centrifuge microscope was introduced, with which the behavior of the cells under arbitrary contact forces could be observed. Motion of HL-60 cells, well-known model cells of neutrophils, on some substrates was observed using this microscope. It was shown that the contact force considerably influences the motion of the cells. Consequently, it can be concluded that it is necessary to take into consideration the contact force when observing the interaction between neutrophils and the endothelium.

View full abstract

A personalized healthcare has been emerging in recent remarkable progress in medical technology. From this point of view, an importance of the miniaturized device for blood analysis is growing. This article introduces our research about the development of microdevice for blood analysis, especially flow cytometer chip, in which flow visualization play a significant role in the development process. Hydrodynamic focusing essential in the precise analysis was evaluated by three-dimensional flow visualization using a fluorescent dye. As a result, we confirmed that our proposed device has a good performance in hydrodynamic focusing. Based on the result, an integrated flow cytometer chip with embedded optics such as mirror was developed.

View full abstract