How a robotic thread could improve treatment for brain aneurysms, strokes

With its thread-like thinness and coating of slippery hydrogel, a newly developed robotic guidewire may allow surgeons to quickly navigate the brain’s narrow, winding pathways to treat aneurysms and strokes.

As described in the journal Science Robotics, engineers from Massachusetts Institute of Technology (MIT) have created a “magnetically steerable” robotic thread that surgeons can remotely direct through the brain’s intricate system of blood vessels to quickly deliver clot-reducing therapies and other treatments for brain blockages and lesions.

“Stroke is the number five cause of death and a leading cause of disability in the United States,” Xuanhe Zhao, associate professor of mechanical engineering and of civil and environmental engineering at MIT, said in a press release about his team’s work Tuesday.

“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.”

The current treatment for strokes and aneurysms involves a minimally invasive endovascular procedure in which the surgeon inserts a thin wire through one of the patient’s main arteries, such as in the leg or groin.

Guided by a fluoroscope, an instrument that allows doctors to view inside the body using X-rays, the surgeon manually rotates the wire into the affected brain vessel. The wire is then used to thread up a catheter, drugs, or clot-retrieval devices to treat the damaged region of the brain.

The developers of the robotic thread said the conventional guidewire is passive and requires surgeons specifically trained in the task to use them. Another potential drawback is the core of the wire is made of metallic alloys coated in polymer, which the researchers say could potentially create friction and damage vessel linings if it were to become stuck in a particularly narrow pathway.

The research paper’s lead author, Yoonho Kim, a graduate student in MIT’s Department of Mechanical Engineering, said the current procedure is taxing for surgeons, who put themselves at risk of repeated radiation exposure due to their close proximity to the fluoroscopy.

“It’s a demanding skill, and there are simply not enough surgeons for the patients, especially in suburban or rural areas,” Kim said.

To improve on this treatment, the MIT researchers combined their work in hydrogels, which are biocompatible consisting mostly of water, and magnetic actuation, or converting electric currents into mechanical output, to produce the robotic thread.

What distinguishes the robot thread from a conventional wire is its nickel-titanium alloy core, which is “bendy and springy” and its coating of hydrogel. These materials allow the robotic thread “more flexibility in winding through tight, tortuous vessels.”

Additionally, the hydrogel coating the robotic thread provides the wire with a smooth, friction-free, biocompatible surface.

“When the researchers ran comparisons between the robotic thread coated versus uncoated with hydrogel, they found that the hydrogel gave the thread a much-needed, slippery advantage, allowing it to glide through tighter spaces without getting stuck,” the press release said.

The coating also doesn’t interfere with the thread’s magnetic particles, the researchers said, allowing it to be guided with a magnet outside the body.

The robotic thread was tested in a life-size silicone replica of the brain’s major blood vessels, including clots and aneurysms, according to the team. They were also able to demonstrate the thread’s ability to carry out other functions, such as delivering clot-reducing drugs and breaking up blockages with laser light.

As for reducing radiation exposure to surgeons, Kim said the magnetic component of the robotic thread removes the need for surgeons to physically push a wire through the patient’s blood vessels, which means they won’t be as close to the patient and the radiation-generating fluoroscope.

“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,” Kim said.

The researchers said their next goal is to test their robotic thread in living beings.

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