Doctors may soon be able to steer a catheter through blood vessels via remote control. Catheters-long, flexible tubes-are used for biopsies, drug delivery, and other crucial medical tasks. Manually maneuvering a catheter to its target requires a doctor to push and rotate the outside end while monitoring the progress via x-rays. The new navigation method, under development by radiologist Ronald Arenson at the University of California, San Francisco, uses magnetic technology. The catheter’s tip is encircled by copper coils. As the patient lies within a magnetic field, a doctor uses a joystick to control the flow of electrical current to the coils; the current causes the catheter to realign itself with respect to the field. Such fine control, says Arenson, “will allow us to get to parts of the brain and body that are not easily accessible right now.” Arenson says that it will be five to eight years before the system is approved for human use.