Journey to the center of a tumor

In this paper, a hospital technician in Montreal slid the limp body of an anesthetized pig into the tube of a magnetic resonance imaging machine, or MRI. A catheter extended from a large blood vessel below its neck-a carotid artery. Into the catheter, a surgeon injected a steel bead slightly larger than the ball of a ballpoint pen. In a room next door, a program designed to manipulate the machine's magnetic forces, which would guide the bead like a remote-controlled submarine was tested.