Mechanisms of ultrasonic thrombolysis

An ultrasonic transversely vibrating wire delivers energy to an active zone to facilitate thrombolysis in a blood vessel. Ultimately, all the energy delivered into the treatment region at the active zone ends up as heat. The heat created can originate from three sources. The first source of heat is from stresses in the waveguide and resultant internal frictional losses of the material; this heat is conducted into the fluid surrounding the waveguide. The second source of heat is from absorption due to acoustic propagation through the fluid. The third source of heat is from viscous losses as the wire moves through the fluid. This paper determines that the average power of an Omniwave ultrasonic thrombolysis system running in a single 20 kHz transverse mode with a 120 micrometer peak-to-peak amplitude is about 1.3 Watts due primarily to viscous losses.