Velocity field measurements of blood flows using a synchrotron x-ray imaging technique

The x-ray PIV technique was employed to measure instantaneous velocity fields of blood flow in an opaque microchannel. Generally, it is difficult for conventional clinical instruments to visualize detailed transport of blood cells or to acquire quantitative hemodynamic information due to poor spatial resolution. On the other hand, although conventional PIV techniques have higher spatial resolution, they can be applicable only to transparent fluids inside a clear conduit. In addition, seeding particles indispensable for PIV measurements can affect the biochemical characteristics of blood. In order to resolve these problems, we established an x-ray PIV technique by using a permeable x-ray beam as a light source of PIV technique. For acquiring good x-ray images of red blood cells from which velocity vectors can be extracted, the sample-detector distance and the thickness of sample fluid were optimized. By applying 2-frame PIV algorithm to the acquired x-ray images of red blood cells, the quantitative velocity field information was obtained. The measured velocity data of blood flow show typical flow characteristics in a macrochannel.