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Biomedicine

Snakelike Robots for Heart Surgery

More-flexible robots could allow for less-invasive operations.

A snakelike surgical robot from Carnegie Mellon University could let a surgeon performing a critical heart operation make just one incision.

Ready to probe: The CardioArm can wiggle its way inside a body and perform cardiac ablations. An operator controls the robot’s motions using a joystick.

Known as the CardioArm, the curved robot has a series of joints that automatically adjust to follow the course plotted by the robot’s head. This provides greater precision than a flexible endoscope can offer. “It’s certainly easier to control,” says Robert Webster III, a professor at Vanderbilt University who works on flexible medical probes and was not involved in the CardioArm project.

The CardioArm is operated using a computer and a joystick. It has 102 degrees of freedom, three of which can be activated at once. This allows it to enter through a single point in the chest and wrap around the heart until it reaches the right spot to, say, remove problematic tissue. “The nice thing about [the] design is that each joint follows where you went in space. That’s not always possible in other designs,” says Webster. This kind of control prevents the probe from bumping into sensitive tissue. The disadvantage of a jointed robot, however, is that it’s harder to miniaturize, Webster says.

The smallest version of the device is 300 millimeters long and has a diameter of 12 millimeters. Eventually, the CMU researchers hope to make a snake small enough to enter the bloodstream through a blood vessel, says Marco Zenati, one of the principal researchers on the CardioArm project and a professor of surgery at the University of Pittsburgh.

Zenati has used robotic surgical assistants in the past and notes that they all have limitations. The da Vinci system, for example, can’t “squeeze into tight locations within the human body” and requires five or six entryways, he says.

Realizing the need for more-advanced robots for minimally invasive surgery, Zenati teamed up with Howie Choset, a TR35 honoree known for his work at CMU on crawling robotic snakes, and Alon Wolf, founder and director of the Biorobotics and Biometrics Lab at Technion, the Israel Institute of Technology.

“We are working to just have a single port in the body and from that point being able to reach any location,” says Zenati. “There is no technology that allows one to do that. The only one is the CardioArm.”

The probe is currently being developed by the startup Cardiorobotics, formerly known as Innovention Technologies, which Zenati and Choset founded in 2005. So far, the team has performed successful cardiovascular surgeries on nine pigs and two human cadavers, says Choset. According to the company’s website, live human trials should begin later this year.

Snakes in hearts: The snakelike CardioArm moves around inside the membrane encasing a pig’s heart.

“For minimally invasive surgery, you either have a linear laparoscope that’s rigid or a flexible endoscope that buckles easily; there’s nothing that’s both flexible and rigid,” says Choset. But the CardioArm “has the benefits of both,” he says.

“I think what Howie has is a good platform for getting at the [surgical] site,” says Nabil Simaan, an assistant professor at Columbia University who is working on insertable, snakelike probes for the abdomen.

The team hopes to start testing the CardioArm in natural-orifice surgery–a technique where tissues are removed through existing openings in the body, such as the mouth, to avoid postoperative pain and reduce recovery time. Zenati aims to have surgeons use CardioArms in unison, like “an octopus, with two or three tentacles” all entering through one incision and then branching out.

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