Radiology: Into the Brain's Labyrinth

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Doctors were proud when they devised ways of using magnets to extract iron and steel objects from patients—usually nails and safety pins from children's gullets or stomachs. Now they are carrying the idea much farther by inserting magnets to get at hitherto inaccessible parts of the human body.

One of the most formidably inaccessible places is the labyrinth of arteries inside the brain. But at the latest meeting of the American Roentgen Ray Society, Dr. Sadek K. Hilal demonstrated a catheter with a magnetic tip that "swims" through small and tortuous arteries and can be guided to the exact spot that the radiologist or neurologist wants to reach.

The catheter is a thin tube of Silastic (silicone rubber). To reach the brain's remote fastnesses, a plastic sleeve is inserted in the carotid artery in the neck and the catheter is threaded through it. Earlier catheters were often stopped by friction and could not always be guided into the desired path at a junction or around sharp curves. The new model, developed in research at Manhattan's Columbia-Presbyterian Medical Center and at the Weizmann Institute in Israel, has a magnetic tip. This can be made to oscillate in different directions under the control of an external magnet on alternating current. As the tip vibrates, it pulls clear of the artery's walls, leaving them undamaged, and "swims" forward. When the magnet is powered by direct current, it helps to steer the device.

Near the magnetic tip are two small slits in the rubber tube. With a syringe attached at the neck opening, the doctor can inject a dye opaque to X rays at the precise spot where an arterial abnormality is suspected and see the vessels clearly outlined on the screen of a fluoroscope. It may be possible, said Dr. Hilal, to use the catheter to inject substances to seal off weak spots in ballooned-out arteries, or to inject anti-cancer drugs into brain tumors.