Blood clots can spell trouble wherever they occur, but those that form in the brain can be especially dangerous when they give rise to outcomes like aneurysms and strokes. Mechanical engineers at MIT have developed a slender new device built to snake its way through the brain’s blood vessels and tend to such blockages, promising safer forms of treatment for not just the patient, but the surgeons involved as well.
“Stroke is the number five cause of death and a leading cause of disability in the United States," says Xuanhe Zhao, associate professor of mechanical engineering at MIT. "If acute stroke can be treated within the first 90 minutes or so, patients’ survival rates could increase significantly. If we could design a device to reverse blood vessel blockage within this ‘golden hour,’ we could potentially avoid permanent brain damage. That’s our hope.”
Current approaches to clearing clots in the brain typically involve endovascular surgery, where a thin wire is fed through a main artery via the leg and up into the brain, guided by a fluoroscope. The wires are generally metallic and polymer, which can cause friction or cause them to get stuck in tight places, according to the MIT team. This isn’t pleasant for anyone involved, either the patient who has to endure the experience or surgeons who have to manually feed the wire into the brain, exposing themselves to radiation courtesy of the fluoroscopy.
Borrowing from the research realms of soft robotics and biocompatible hydrogels, the MIT team has now developed a rather promising alternative. They actually describe the device as a robotic thread, in the sense that it can be controlled remotely using magnets.
The wire consists of nickel-titanium alloy at its core, which affords it a flexible and springy form so it can wind around any corners it might encounter. This was then coated with a rubbery paste that features magnetic particles throughout, and finished with a hydrogel to give it a friction-free, biocompatible exterior.
The team tested the thread out through a series of experiments, including one involving a life-sized silicone replica of the major blood vessels in the brain complete with clots and aneurysms, and with channels filled with a thick liquid to simulate blood. The researchers liken control of the robotic thread to pulling the strings of a marionette, and were able to steer the wire through the replica’s narrow paths.
Additionally, the scientists hope to expand functionality of their robotic thread with certain modifications, such as fixing a device for drug delivery to the end or to treat clots using light. To explore they latter possibility, they also ran experiments with an optical fiber at the thread's core rather than the nickel-titanium alloy, and were able to successfully steer the wire to a destination and then fire up the laser.
Overall, the MIT team says the wire has the potential to better navigate the complex and intricate web of blood vessels in the brain than current devices. Other advantages include a smoother exterior that is less prone to friction, and the ability for surgeons to avoid radiation exposure because the wire can be controlled remotely through a magnetic field.
“Existing platforms could apply magnetic field and do the fluoroscopy procedure at the same time to the patient, and the doctor could be in the other room, or even in a different city, controlling the magnetic field with a joystick,” says Yoonho Kim, lead author on the study. “Our hope is to leverage existing technologies to test our robotic thread in vivo in the next step.”
The team's research was published in the journal Science Robotics, while the video below shows the robotic thread in action.
Source: MIT