Measuring thrombolysis in a static model to assess ultrasound protocol efficacy

Abstract

Over the years, EKOS has developed an efficacy measure called Lysis Enhancement Factor (LEF) to evaluate the performance of prototype ultrasound catheters and acoustic protocols. LEF is defined as the percent increase in the rate of lysis compared to tPA alone as measured in our simple clot model consisting of a plasma clot in a static tube. The amount of thrombolysis can be measured by determining the change in fibrin weight compared to control clots. The LEF is expressed as a percent change in the thrombolysis rate compared to lytic control. When the EkoSonic catheter was initially launched, the in vitro LEF was about 50% using a constant amplitude pulsed ultrasound protocol with an average power of 2.7 W per transducer group. Later, the MACH4 ultrasound protocol was introduced with an LEF of about 70%. This protocol had a higher average power (3.5W) and consisted of variable pulse amplitudes, which were randomly sequenced. Further investigations with the clot model lead to the development of the currently marketed MACH4e protocol with an LEF of about 90% but with variable amplitude pulses, which cycle up and down. The clot model and LEF are being used to further develop EKOS’ technologies.