A semi-flexible wearable ultrasound probe for enhancing catheter-directed thrombolysis: an in-vitro study

Catheter-directed thrombolysis (CDT) is a commonly treatment for blood clots, but it requires large urokinase doses and carries bleeding risks. Therapeutic ultrasound has shown ability in enhancing thrombolysis, but existing ultrasound thrombolysis strategy is not suitable for long-term operation. This study had developed a semi-flexible wearable ultrasound probe (sf-WUP) to enhance effectiveness of CDT in heavy thrombus burden with low-dose urokinase. The sf-WUP was bent to focus on the thrombus and transmit either single-frequency ultrasound at 1.8 MHz or dual-frequency ultrasound (1.8 MHz and 1.88 MHz). The catheter was used to deliver low-dose urokinase or a combination of urokinase and microbubbles to the target thrombus. Thrombolysis extent was the thrombus mass reduction percentage. In 50 min, the thrombolysis extent of low-dose urokinase was only 11.40%, while the sf-WUP using single-frequency ultrasound with microbubbles increased to 55.23%. Under constant acoustic power, the dual-frequency ultrasound reached a thrombolysis extent of 63.78%. When the peak-to-peak sound pressure was kept constant, the dual-frequency ultrasound achieved a similar thrombolysis extent but with 9.75%-13.84% lower electrical power compared to single-frequency ultrasound. The sf-WUP using single-frequency ultrasound can significantly improve the thrombolysis extent of low-dose urokinase CDT. The use of dual-frequency ultrasound with constant power can further enhance efficiency, while dual-frequency ultrasound with constant peak-to-peak sound pressure shows better energy efficiency. Both are compatible with wearable devices, laying the foundation for the clinical translation of ultrasound assisted CDT.