T Hölscher, DJ Fisher, R Raman, K Ernstrom, E Zadicario, WG Bradley and A Voie
Background: Initial data using transcranial ultrasound in combination with tissue Plasminogen Activator (tPA) for sonothrombolysis in stroke are promising. However, absorption and defocusing of the ultrasound beam occur during transskull insonation, limiting the efficiency of this approach to high extent. The purpose of this in vitro study was to investigate whether transcranial sonothrombolysis can be achieved using High Intensity Focused Ultrasound (HIFU) without the use of tPA. Methods and Results: Transskull clot lysis (N=420) using a novel HIFU head system was performed using an in vitro flow model. Experiments were performed using varying acoustic output powers, changing flow conditions, and different cadaveric skulls. Human whole blood clots (3 hours incubation) could be lysed within less than 30 seconds and in absence of further lytic agents. Thrombolysis efficacy was dependent on transskull signal absorption, acoustic output power and flow conditions and differed widely between a minimum of 6.21% and a maximum of 77.26%. Transskull insonation with HIFU did not lead to significant focus beam distortion. Conclusions: The use of transskull HIFU for immediate clot lysis without the need of further drugs and disregarding individual skull bone characteristics is feasible in vitro.