Abstract
Active Strobe Imager can visualize a high-speed cyclical motion by using an air-jet and a storbe. We can observe "ischemia" visually with Active Strobe Imager during the impartment of an air-jet. Ischemia is the phenomenon of a change of surface color from red to white because of pressing a blood vessel. The purpose of this work is to discuss the parameter influence on the Active Strobe Imager and the critical frequency where ischemia never recovers completely at any higher frequency. We show that the duty ratio changes ischemia patterns and the critical frequency may be available as an index for judging how healthy the tissue is.