MRI-powered medical robots are coming

It began as a proof-of-principle demonstrated with LEGOs – a surgical biopsy needle whose motor is driven solely by a clinical MRI scanner:

The above demo shows that an MRI machine’s magnetic field can be programmed to produce enough force to control a robotic instrument — an accomplishment with broad potential in medicine. In the demo, the scanner’s magnetic field swings a rotating arm, and a set of gears convert that motion into the motion of a biopsy needle, strong enough to puncture the tough outer tissue of an animal heart and then withdraw. All parts exposed to the magnetic field are metal-free and MRI-compatible.

While MRI-compatible robots have been built before, this was the first demo of a motor powered by MRI, says Pierre Dupont, chief of Pediatric Cardiac Bioengineering at Children’s Hospital Boston. His engineering team was one of five finalists for Best Paper Award — out of 790 papers presented — at last week’s International Conference on Intelligent Robots and Systems (IROS 2011). The paper’s first author was Panagiotis Vartholomeos of Children’s, and the system was tested in collaboration with Lei Qin of Brigham and Women’s Hospital.

But Dupont’s vision for the technology is much broader than simply doing biopsies.

“Our ultimate goal is to create magnetically powered robots that can either travel through the body to perform highly targeted therapies or reside inside the body as adjustable prosthetic devices,” he says.

That might include ball-bearing-sized robots that could be steered through the cerebrospinal fluid or the urinary system to deliver drugs or stem cells. Or implantable devices that could be adjusted to regulate blood flow in the heart. Or implants for children that could be gradually enlarged as they grow, preventing the need for repeat operations to place larger implants.

A number of engineering challenges lie ahead – such as how to get the MRI machine to image and drive a device at the same time.  “You need to use MRI to not only power the device, but also to monitor the device and its interaction with the body,” says Dupont.

Another challenge being tackled in the lab is to get magnetic fields to steer swarms of tiny, injectable robots to different destinations in the body. While magnetic control of a single “swimming robot” has been demonstrated in a blood vessel and inside the eye, no one has figured out how to use the same magnetic fields to control many robots at once. “This is important, because it may be necessary to target many locations inside the body or simply to deliver a larger quantity of drug than one robot can hold,” Dupont says.

His team recently showed that an MRI magnetic field can independently control two robots at once, and just submitted another paper demonstrating its first results in multi-robot control, using differences in how each robot speeds up and slows down to tweak the robots’ individual swimming speeds. “Right now, we’re telling the robots where to go,” says Dupont. “Ultimately, we want them to figure that out for themselves.”

Ed. note: Read about the robot and special tools Dupont’s team designed for beating-heart surgery.