If you have a pacemaker monitoring your heart, you'd better hope nothing goes wrong with your mind. That's because MRIsthe most effective way to image the brainand pacemakers don't mix. The former heats the device's implanted metal wires so much they could scar the heart or trigger a rapid heartbeat. Now, Wilson Greatbatch, inventor of the pacemaker, has teamed with Biophan Technologies to create a fiber-optic cable impervious to the MRI's magnetic waves. Instead of using electricity directly, it jolts the heart with laser energy converted to an electric charge.