Monday, 14 October 2013

Robot uses steerable needles to treat brain clots

collaboration between Vanderbilt mechanical engineer Robert Webster and neurosurgeon Kyle Weaver has designed a special robotic system that uses tiny, steerable needles to suction out brain clots formed by intracranial hemorrhaging.

Blood clot simulation

It is an image-guided surgical system. It 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 intracerebral hemorrhage are one in 50 over his or her lifetime. When it does occur, 40 percent of the individuals die within a month. Many of the survivors have serious brain damage. So 0.8% of people will be killed by intracerebral hemorrhage and almost 1% get brain damaged by it.

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. The single needle system required for removing brain clots was actually much simpler than the multi-needle transnasal system.

According to the feasibility studies the researchers have performed, the robot can remove up to 92 percent of simulated blood clots. Surgeons generally agree that there is a clinical benefit from removing 25-50 percent of a clot but that benefit can be offset by the damage that is done to the surrounding tissue when the clot is removed. Therefore, when a serious clot is detected in the brain, doctors take a “watchful waiting” approach – administering drugs that decrease the swelling around the clot in hopes that this will be enough to make the patient improve without surgery.

Removing 92% or all of the clot would be a huge difference and a big clinical benefit.

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.

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. 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.

“The trickiest part of the operation comes after you have removed a substantial amount of the clot. External pressure can cause the edges of the clot to partially collapse making it difficult to keep track of the clot’s boundaries,” said Webster.

The goal of a future project is to add ultrasound imaging combined with a computer model of how brain tissue deforms to ensure that all of the desired clot material can be removed safely and effectively.

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