Mini Robot Enters Blood Vessels, Completes Surgery

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This article is part of our exclusive IEEE Journal Watch series in partnership with IEEE Xplore.

When a patient has a blocked artery or blood vessel, a team of surgeons must carefully thread an ultrathin catheter through the person’s blood vessel to reach the lesion or blocked area. But whereas surgeons must estimate the position of the catheter from outside the patient’s body using X-rays, miniature robots traveling through blood vessels could offer a more precise and easy way to access the treatment site.

Many research teams are exploring this possibility, and one team in South Korea recently found success when their robot was able to navigate autonomously to an artery in a pig, deliver contrast dye, and safely navigate back to an extraction point. The results were published 9 February inIEEE Robotics and Automation Letters.

[embedded content]Small Magnetic Robot Completes Vascular

Occlusive vascular disease, or OVD—including stroke in the brain, myocardial infarction in the heart, or peripheral artery disease in the limbs—is a major cause of death, and is expected to become more prevalent as society ages and obesity increases. Surgical interventions to clear blocked arteries and vessels are a key treatment option for serious cases and can save lives, but these surgeries come with some major challenges.

Besides the difficulty that surgeons face in manually guiding surgical tools through blood vessels to the lesion area, surgeons must rely on X-rays to guide their equipment, which inadvertently exposes health-care teams to high-dose radiation from X-ray imaging devices.

“[The procedure involves] long hours of operation because it is hard to accurately target a lesion if the blood vessel has a complex shape or is totally blocked,” explains Gunhee Jang, a Distinguished Professor at Hanyang University, in Seoul, who was involved in the study.

To address these issues, Jang’s team came up with a solution using an untethered robot that’s guided externally by magnets. That’s where the I-RAMAN (robotically assisted magnetic navigation system for endovascular intervention) robot gets its name.

First, the Hanyang team developed software that uses 2D X-ray images shot from different angles to create a 3D map of the patient’s blood vessels surrounding the blocked area. The tethered magnetic robot can use the 3D map to navigate autonomously and perform treatments such as tunneling through the lesion.

A catheter is used to inject the robot into a blood vessel near the treatment area, and the external magnetic field is used to create rotational motion to untether the robot from the catheter. The external magnetic field is then used to guide the robot to the treatment spot, relying on the 3D map to navigate.

Once the robot arrives at the part of the artery or blood vessel that needs treatment, it can perform a number of tasks, including ballooning, suctioning blood clots, and localized delivery of contrast dye or drugs. Once the robot’s task is complete, the external magnetic system guides the robot back to the catheter, and the robot is removed from the body.

In their study, the researchers first tested the technique in an artificial blood vessel floating in a water tank, which proved successful. Next, they put their robot to the test in the superficial femoral arteries of small pigs under anesthesia.

“We were very confident of performing robotic endovascular intervention in the [artificial] blood vessel,” says Jang. “But during the in vivo experiment in a superficial femoral artery of the mini pig, we noticed that it is a quite different and difficult world.”

Over the course of a year, they partnered with cardiologists and completed eight surgeries in pigs. The final experiment proved successful, offering proof of concept that the technique is feasible in real life.

Jang’s team plans to continue its work with the goal of commercializing their I-RAMAN system, and they have established a bio-venture company named InterMag.

Jang notes that these recent experiments in pigs have revealed ways to improve upon the microrobot as well as the magnetic navigation system. “Specifically, we will increase the magnetic field generated by the magnetic navigation system, and we plan to decrease the size of the microrobot and design it efficiently,” he explains. Additionally, Jang says, the team also plans to apply to the Korean Ministry of Food and Drug Safety to undertake clinical trials of the magnetic robot system.

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