If you have a pacemaker monitoring your heart, you'd better hope nothing goes wrong with your mind. That's because MRIs–the most effective way to image the brain–and 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. The device should enter clinical trials in two years.