Groovy '70s sound keeps X rays tight.

Instead of nostalgia, perhaps it was uncanny foresight that led some people to keep their obsolete long-playing records all these years. A team of Swedish and American scientists has now put a new spin on the old platters--using them to focus X rays, on the cheap.

The inventors aim to employ their novel LP-based lens to make X rays converge in an innovative mammography machine. They speculate that the lens' combination of rock-bottom price, decent performance, and easily adjustable focal length may make it attractive for other medical applications as well. Versions made of materials tougher than vinyl may even prove useful for large electron-accelerator--based X-ray sources known as synchrotrons, they say.

"It's X-ray optics for the layman," says Bjorn Cederstrom of the Royal Institute of Technology in Stockholm. "You don't need loads of money and equipment to do this." He and his colleagues at the institute and at Lawrence Berkeley (Calif.) National Laboratory describe their innovation in the April 27 NATURE.

To make a lens, the researchers snip two 6-centimeter-long rectangular slabs out of a record and place them one atop the other like a pair of jaws. The record's grooves give the resulting mouth many triangular teeth. The difference in the speed with which X rays pass through the teeth and air causes the beams to refract, acting like a lens, Cederstrom explains.

Ultimately, the scientists didn't end up using ordinary LPs to make lenses, he notes. Their grooves were too shallow and too far apart, so the team custom-ordered new, improved LPs.

Better keep that old phonograph after all.