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Corkscrew fiber retrieves blood clots

10 Oct 2005

Stroke victims could benefit from a laser-activated polymer that changes shape to capture blood clots.

A thin, straight polymer that takes the shape of a corkscrew when heated by a laser could help surgeons remove blood clots from stroke patients. The device, developed by researchers at Lawrence Livermore National Laboratory (LLNL), US, may offer a safer alternative to clot dissolving therapy and could extend the treatment window from three to eight hours following a stroke. (OPTICS EXPRESS 13 8204)

"The system is comprised of a near infrared diode laser coupled to a shape memory polymer (SMP) micro-actuator using an optical fiber," LLNL researcher Ward Small told Optics.org. "The laser light is absorbed by a thin surface layer of a platinum dye, generating heat, which causes the SMP to transform into its pre-programmed corkscrew shape."

The polyurethane-based SMP device is connected to a diode laser emitting around 5 W at 810 nm. Immersed in water at body temperature, the polymer changes shape from a straight rod into a 10 mm long spiral structure with a diameter of 3 mm in just 3 seconds when irradiated.

The scientists have tested their device using an artificial blood clot inserted into an experimental model of a carotid artery. The polymer device was pushed into the artificial clot, activated and used to pull back the occlusion against the flow.

Currently, the group is discussing its technology with medical device manufacturers and plans to conduct animal studies to further evaluate the technique. "Based on previous experience with another SMP-based interventional device, human trials could potentially begin 12 to 18 months after reaching a licensing agreement," said Small.

Researchers estimate that laser heating of the polymer would raise the temperature of surrounding blood by around 12 degrees, which can be sustained for around 15 minutes without causing permanent tissue damage.

James Tyrrell is reporter on Optics.org and Opto & Laser Europe magazine.

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