Ultrasound-guided probe device: When doctors inject a patient with a needle, they cannot see what they are getting themselves into. Underneath the skin, where they hope there is a vein waiting to be tapped, is a dark, mysterious world. This struck Stephen Ridley, now president and chief medical officer of Soma Access Systems in Greenville, S.C., as a problem. “You literally do this blind,” he says.

Ultrasound can help image tissues that are inside, but it is bad at imaging the needle itself. The needle's round, metallic surface simply scatters the ultrasonic waves and basically appears invisible. So Ridley, whose background is in engineering and medicine, designed a potential solution: combining ultrasound and magnets. The ultrasound shows the tissue, and a small magnet at the tip of the needle is picked up by an array of magnets in the ultrasound probe. The magnetic field generated does not interfere with the ultrasound and allows doctors to see both the tissue they are piercing and the needle they are piercing it with. The system helps them line up their needle beforehand, removing much of the guesswork they have dealt with before.