Magnetic Surgery -- Radically New Type Of Medical Procedure Tested On First Patient

"This is a fundamentally new way of manipulating surgical tools within the brain that promises to be minimally invasive," says Ralph Dacey, M.D. "And it should be a safer way of doing brain surgery because it allows us to use a curved pathway to reach a target. Therefore we can go around sensitive structures, such as those that control speech or vision, instead of going through them."

Dacey is the Edith R. and Henry G. Schwartz Professor and head of neurological surgery at Washington University School of Medicine in St. Louis. He is testing the new technology, called the Magnetic Surgery System (MSS), by biopsying five patients with tumors in the upper front part of the brain. A biopsy removes a small piece of tissue, enabling physicians to identify a tumor, determine whether it is malignant and plan appropriate treatment.

The first patient, a 31-year-old man, underwent the magnetic surgery Dec. 17 at Barnes-Jewish Hospital in St. Louis. Dacey used computer-controlled superconducting magnets to remotely direct a small flexible biopsy instrument into the patient’s brain.

This advanced medical technology has been under development for more than a decade at universities and national laboratories throughout the United States. A St. Louis-based company called Stereotaxis Inc. is spearheading its commercial development.

"We expect the system to have a wide range of applications because it puts three components – visualization, localization and navigation – together for the first time, creating an interventional workstation," says Bevil Hogg, the company’s CEO. "Future possibilities may include implanting electrodes into the brains of patients with movement disorders, repair of aneurysms and other blood vessel abnormalities, delivering therapeutic drugs or chemotherapy agents to parts of the brain, cardiac electrophysiology and removal of arterial plaque."

Surgeons currently use images of the brain to see a tumor, and they can localize instruments that have sensors. But until now, there has been no way to automatically navigate tools through the brain along an optimal path. To obtain a biopsy, for example, neurosurgeons manually push a rigid needle toward a tumor, passing through whatever lies en route. The MSS, which looks like a magnetic resonance imager, directs a catheter to a predetermined part of the brain along a pathway planned by the surgeon.

Matthew A. Howard III, M.D., associate professor of neurosurgery at the University of Iowa, and M. Sean Grady, M.D., professor of neurosurgery at the University of Washington, accompanied Dacey during the surgery. Howard and Grady are co-inventors of the original magnetic surgery system, along with Rogers Ritter, Ph.D., professor of physics at the University of Virginia. Howard conceived the idea in 1984, when he was a medical student at the University of Virginia.

Last week’s surgery began when Dacey drilled a finger-sized hole in the patient’s skull. He placed a plastic bolt in the hole to provide a subsequent entryway for surgical instruments. He also attached six small metal markers to the outside of the skull to enable the computer to localize the catheter (see attached backgrounder).

Dacey then viewed magnetic resonance images (MRIs) of the patient’s brain on the screen of a computer console. The 3-D views and virtual slices through the brain allowed him to plan the best route to the tumor.

The surgeons next placed the patient’s head in the MSS, positioning it between the superconducting magnets with a titanium frame. Opening the plastic bolt in the skull, they introduced a tiny magnet into the brain. The magnet was attached to a guidewire, which was covered by a plastic catheter. "The catheter is much narrower than a drinking straw but a bit fatter than spaghetti," says Andrew F. Hall, D.Sc., the company’s cardiovascular program manager.

Sitting at the computer console, Dacey guided the small magnet to the tumor. As the magnet moved along the preplanned path, the computer advanced the guidewire and catheter one millimeter at a time, always checking the trajectory.

After the magnet reached the tumor – about a 5-minute trip – Dacey gently pulled it and the guidewire out of the brain, leaving the catheter in place to act as a tunnel. He then inserted a specially designed biopsy tool along the catheter. Because the tool was flexible, it followed the preplanned path. A few minutes later, Dacey had snipped out a tissue sample for the pathology lab. After taking additional samples from other parts of the tumor, he removed the catheter and cranial bolt and closed the small hole in the skull.

"This is the first time magnetic surgery has been done anywhere in the world," Dacey says. "It eventually should allow us to be much more innovative in delivering electrodes or drugs for direct therapy of a variety of brain diseases."