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Blood Clots Could Possibly Be Removed via Robot-Based/Medical Imaging and Steerable Needles

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A robot-based surgical system is currently in development at Vanderbilt University. The robotic system is designed to utilize steerable needles and medical imaging technology to gain access to the brain and removing fatal blood clots with minimal damage being done to the surrounding brain region.

Based on a press release by Vandebilt University, assistant professor Robert J. Webster III and his team had been working on a steerable needle system for transnasal surgery for over the last four years. Blood Clots Could Possibly Be Removed via Robot-Based Medical Imaging and Steerable Needles

Webster was primarily focused on mechanics that included the removal of tumors  in the pituitary gland and at the skull base that normally involve cutting large openings in the skull or face. It wasn’t only until he attended a conference in Italy and heard Marc Simard, a neurosurgeon at the University of Maryland School of Medicine, discussing the usefulness and effectiveness of utilizing a needle-sized robot arm that reaches into the brain to remove clots. Taken with the idea, Webster determined it was a viable option and pursued the new technology’s construction and development.

The system, which Webster calls an active cannula, is comprised of thin, nested tubes that each have their own intrinsic curvature. By rotating, extending, and retracting the tubes, a surgeon can guide the tip in several directions, allowing it to follow a curving path. The system, which is much simpler than the previous transnasal concept, operates by first calculating the exact location of a blood clot by using a CT scan. Once the position is determined, the surgeon picks the best entry point on the skull and the appropriate insertion angle for the probe. The angle is dialed into a fixture called a trajectory stem, which is attached to the skull immediately above a small hole that has been drilled.

From there, the surgeon positions the robot so it can insert a straight outer tube through the trajectory stem and into the brain. The surgeon then chooses the smaller inner tube with the curvature that best fits and aligns itself with the shape of the clot, and attaches a suction pump to the external end piece and places it in the tube.

Using CT scan imaging as a source of navigation, the robot then inserts the outer tube into the brain until it nearly reaches the surface of the blood clot, then inserts the inner tube into the clot and the pump is activated, which then proceeds to suck out the blood clot.  The robot rotates, extends, and retracts the tubes to remove the clot. The team reports that the robot was able to remove up to 92% of simulated blood clots in a series of feasibility studies.

However, Webster notes a chink in the technology that still requires sorting out. It comes after the removal of the majority of the clot when external pressure can cause the edges of the clot to partially collapse, which makes it difficult to track the clot’s boundaries. 

In future developments, the team hopes to add ultrasound imaging in conjunction with a computer model of how brain tissue deforms to ensure that all of the clot material can be removed safely and effectively.

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