Robot treats brain clots with steerable needles

Researchers have designed a novel robot-arm system that reaches deep into the brain to remove fatal clots using steerable needles.

The new image-guided surgical system being developed by Vanderbilt University employs steerable needles about the size of those used for biopsies to penetrate the brain with minimal damage and suction away the blood clot that has formed.

The odds of a person getting an intra-cerebral hemorrhage are one in 50 over his or her lifetime. When it does occur, 40 per cent of the individuals die within a month. Many of the survivors have serious brain damage, researchers said.

Researcher Robert J Webster’s design, which he calls an active cannula, consists of a series of thin, nested tubes.

Each tube has a different intrinsic curvature.

By precisely rotating, extending and retracting these tubes, an operator can steer the tip in different directions, allowing it to follow a curving path through the body.

“I think this can save a lot of lives. There are a tremendous number of intra-cerebral hemorrhages and the number is certain to increase as the population ages,” one of the researchers said.

The brain-clot system only needs two tubes: a straight outer tube and a curved inner tube. Both are less than one twentieth of an inch in diameter. When a CT scan has determined the location of the blood clot, the surgeon determines the best point on the skull and the proper insertion angle for the probe.

The angle is dialled into a fixture, called a trajectory stem, which is attached to the skull immediately above a small hole that has been drilled to enable the needle to pass into the patient’s brain.

The surgeon positions the robot so it can insert the straight outer tube through the trajectory stem and into the brain.

He also selects the small inner tube with the curvature that best matches the size and shape of the clot, attaches a suction pump to its external end and places it in the outer tube, researchers said.

Guided by the CT scan, the robot inserts the outer tube into the brain until it reaches the outer surface of the clot.

Then it extends the curved, inner tube into the clot’s interior, they said.

The pump is turned on and the tube begins acting like a tiny vacuum cleaner, sucking out the material. The robot moves the tip around the interior of the clot, controlling its motion by rotating, extending and retracting the tubes.

According to the feasibility studies the researchers have performed, the robot can remove up to 92 per cent of simulated blood clots.

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