Device: Image-guided Robot Targets Brain Tumors

Photo: An earlier version of the MINIR

The prototype of the MR imaging-compatible Minimally Invasive Neurosurgical Intracranial Robot (MINIR) designed to enable neurosurgeons to reach and remove brain tumors and greatly improve patient outcomes; © RSNA

Researchers have developed a prototype for an MR imaging-compatible robot designed to enable neurosurgeons to remove brain tumors.

Using maggots to eat away dead human tissue may not seem to have much in common with neurosurgery, but the age-old idea was the inspiration for a trio of researchers to combine robotics and real-time MR brain imaging to treat brain tumors.

Several years ago, Dr. J. Marc Simard, neurosurgeon at the University of Maryland School of Medicine, Baltimore, happened to be watching a television program on the medical use of sterile maggots. Finding it “fascinating,” Simard thought the idea could work with brain tumors — minus the maggots.

“The idea was to develop a very tiny robot that could remove diseased areas while leaving healthy tissue untouched, which of course is one of the major challenges with removing brain tumors,” Simard said.

Simard joined with other experts — Dr. Rao Gullapalli of the University of Maryland, and Dr. Jaydev Desai of the University of Maryland, College Park — to develop the prototype for a minimally invasive neurosurgical intracranial robot (MINIR) they hoped could one day be a huge aid to neurosurgeons in removing difficult-to-reach brain tumors.

“The clinical issue is quite simple,” Gullapalli said. “Current neurosurgery practices — especially those involving resection of deep-seated tumors — are in some sense blinded.”

Based on imaging performed before the surgery, surgeons open the skull and make a large incision in the brain to create a line of sight that allows them to extract the tumor. “The problem is that you can never be quite sure you’ve removed enough of the tumor,” Gullapalli explained. “And because new tissue moves in to replace the tissue that’s been removed, there is a risk of removing some of the healthy tissue.”

The procedure may have to be repeated if the tumor is not completely removed, making it potentially very cumbersome and drawn out — not a “high-confidence surgery,” Gullapalli said. But by dropping the tiny robot down into the tumor area and using MR imaging guidance, surgeons are able to remove the tumor without injuring nearby healthy tissue.

Gullapalli, whose area of expertise is MR, and Desai embarked on the project based on their experience using robots to perform breast biopsies. “Moving from breast to neuro is a huge leap,” he said.

Moreover, marrying robotics and MR imaging to create this new device brought with it a huge challenge — developing a robot that could safely be used inside an MR imaging scanner. “It’s not just the type of material, but its shape that matters,” Gullapalli said. “The shape of any object will deflect the magnetic field somewhat and create image distortion, so we had to work out these details.”

Above all, the device had to be small, Desai said. “We needed something we could maneuver like a finger, but with more freedom,” he said. The actuator—the device that drives the robot—must also be compatible with MR imaging and create enough force to move the robot joint and perform tasks like electro-cauterizing tissue. The latest prototype contains a plastic robot body and shape memory alloy spring actuators that actually sit apart from the robot’s body.; Source: Radiological Society of North America