[Zurück]

B. Devcic-Kuhar, L. Kuznetsova, S. Pfaffenberger, M. Gröschl, J. Wojta, M. Gottsauner-Wolf, W.T. Coakley:
"Sonothrombolysis: Effects and mechanisms of ultrasound";
in: "Book of Abstract, 16th Europ. Congress of Ultrasound in Medicine and Biology (EUROSON)", Tagung, Zagreb/HR, 2004, (eingeladen), ISSN: 1330-4917, S. 126.

Every year millions of people suffer from blood clot-related diseases such as myocardial infarction, stroke or peripheral arterial and graft occlusions. The sooner a clot is lysed, the better the tissue function will be maintained. Transcutaneously applied ultrasound has the potential to enforce pharmacological thrombolysis and to accelerate the process of clot dissolution (sonothrombolysis). The effect of ultrasound action in part appears to be related to an increase of transport of drug through the clots' surface. To prove this assumption, we have developed a new method of visual detection of fibrinolytic reactants within the blood clot. This method, implying clot immobilization within a gel matrix and immunohistochemistry, enabled us to localize fibrinolytic components within the thrombus and to study the effect of ultrasound on their spatial distribution. We have shown for the first time that ultrasound facilitates the access of thrombolytic agent to the deeper layers of the clot, thus leading to significantly faster clot dissolution. The mechanisms by which ultrasound augments enzymatic thrombolysis seem to be complex and still remain widely unclear. Yet, several mechanisms such as acoustic radiation force, acoustic streaming, bubble associated phenomena and heating have been suggested to be responsible for this effect. We studied acoustic streaming within different models of blood vessels by seeding fluorescent particles in solution surrounding the clot and by employing a special epi-microscope for their monitoring. Displacements and velocities of the particles were quantified by using computerized Particle Imaging Velocimetry. We have detected different streaming profiles with different streaming velocities, depending on the experimental set up and the ultrasound parameters used. The results gained from this study will have a great impact on future design of ultrasound systems for targeted enhancement of thrombolysis.