Experimental study on hemolysis in centrifugal blood pumps: Improvement offlow visualization method

To evaluate rotary blood pumps, flow visualization is commonly applied to d etermine the flow patterns in a centrifugal blood pump, which have a relati onship to its hemolytic performance. However, it is very troublesome to vis ualize the flow near the vanes due to the high rotational speed of the impe ller. The rotational speed of the impeller in a centrifugal blood pump is u sually several hundred revolutions per minute. In this study, we combined a high-speed video camera based imaging method and an optical system in whic h the image of the rotating impeller was kept stationary. In the optical sy stem, a prism rotating at half the speed of the impeller reflected the imag e of the impeller. The resultant reflected image was observed by a high-spe ed video camera through a half mirror. With this optical setup, the image t hrough the half mirror became stationary, and the path of a specific tracer particle could be traced for a longer duration. A longer duration of measu rements and better quality of the obtained images were realized through thi s improvement. Movement of a specific tracer from the inlet portion to the outlet portion of the impeller could be examined using the developed method .