Stephen Levy

December 17, 2013

2 Min Read
Microphotography Captures Microbubbles Breaking Up Fibrin Clot

Blood clot

An example sequence from a fast frame camera movie (10 kfps). (a) Prior to ultrasound exposure, this frame shows the fluid channel on the left and fibrin clot to the right. (b) A microbubble brought to the boundary induces repeated local deformations under primary radiation forces associated with successive bursts (0.4 MPa) before penetrating the clot and translating (c). After coalescing with another bubble its translation continues and an intact bubble, along with two daughter bubbles that it has shed, remains after the cessation of ultrasound (d). Ultrasound propagation direction is from left to right. 

Numerous papers have been published that describe the effects of ultrasound-stimulated microbubbles (sonothrombolysis) but until now how the technique actually works had not been addressed. Now Toronto researchers have affixed a high-speed camera to a 3-D microscope to catch the microbubbles in action. From the University of Toronto and the Sunnybrook Research Institute, the researchers have published "Interactions Between Ultrasound Stimulated Microbubbles and Fibrin Clots" in Applied Physics Letters.

Though a video isn't on Youtube (yet), the team saw for the first time that the ultrasound waves pushed the microbubbles, literally driving them through the fibrin clot. This tunneling allowed fluid to enter the clot and degraded the clot's structural integrity, causing it to break up. Lead author Christopher Acconcia says these improvements in understanding how sonothrombolysis works will help researchers develop more sophisticated methods of breaking up blood clots.

Research to date "may only be scratching the surface with respect to effectiveness," said Acconcia. "Our findings provide a tool that can be used to develop more sophisticated sonothrombolysis techniques, which may lead to new tools to safely and efficiently dissolve clots in a clinical setting."

While sonothrombolysis is not yet approved for use on human stroke cases, it seems to be on track for eventual approval. Many animal studies have been accomplished and some human trials have been performed. One recent review of the literature published on NIH's National Center for Biotechnology Information site surveys a crop of controlled trials to assess the current state of the art.

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