PIV is an optical method of fluid visualization using a digital image enhancement technique ; it is used to obtain instantaneous and multipoint velocity in fluids. This is one of the most available methods to measure flow velocity distribution.
The fluid is seeded with tracer particles, which for the purpose of PIV, are generally assumed to faithfully follow the flow dynamics. By measuring the motion of tracer particles, we calculate velocity of the flow being studied. More specifically, we prepare two successive particle images by scattering the incident laser light sheet, and calculate the migration distance and the velocity between particles from the cross-correlation function of these two images.
It has been said that shear stress such as blood pressure and vascular flow deeply involves the onset, the development and the burst of cerebral aneurysm. To solve this problem, many analyses of PIV velocity distribution in cerebral aneurysm have been conducted. In PIV, vascular flow in cerebral aneurysm is measured by letting the fluid through the in-vitro blood circulation model ― the fluid with the viscosity and density similar to those of blood. Many of recent blood measurement are done by two dimensional cross section analyses. However, 3D analysis of the flow velocity distribution in the aneurysm is necessary because the form of cerebral aneurysm is very complicated.
On the other hand, the treatment for cerebral aneurysm, using a coil or a stent, aims at blocking the blood vessel which flows into the aneurysm and decreasing the velocity of the blood flow in the aneurysm. Though it is very important to know the change of blood flow before and after the treatment, the indicator of how the blood flows has not been established.
We are making the blood circulation model with parallel shift in the aneurysm and conducting the 3D analysis of the vascular flow velocity distribution. First, we make the velocity distribution on x-y coordinate by shifting the circulation model in 2-dimensional PIV system. Second, we rotate the model at 90 degrees to make the velocity distribution on y-z coorditate. Finally, we process these two data into calculating the 3-D velocity distribution. Moreover, using this 3D method, we analyze the velocity distribution in the aneurysm when various kinds of liquid flow in the aneurysm, and we provide the indicator of alternation in blood flow.
