Radius Health's x-ray sources work through pyroelectricity--the ability of some materials to produce electrical fields when they're either heated or cooled--and uses an approach developed at the University of California, Los Angeles for controlling the emission of electrons by pyroelectric crystals.

Chemical etching is used to carve wafers of pyroelectric crystals into small tiles, which are then arrayed on top of a resistive heater. "We pattern the surface of the crystal with fine points that allow electrons to leave only at those points," says Gil Travish, a researcher in the university's particle beam physics laboratory and one of the company's cofounders. This ensures a steady beam of electrons that can then be used to generate aligned x-rays suitable for imaging. The crystals used include lithium niobate and lithium tantalate crystals, which are found in telecommunications devices and sensors. "We don't need unusual materials," says Travish.

The tiled wafers are topped with a metal foil that emits x-rays when bombarded by electrons from the crystal beneath. A conventional x-ray tube produces a cone-shaped beam of radiation with a hot spot in the middle, which means radiologists must place patients farther away from the x-ray source to get an image of a larger area--to make up for the loss in intensity over distance, the energy of the radiation has to be increased. The new system produces uniform, parallel rays that should have advantages when imaging large areas, says Travish.

Another company, Xintek, is developing a novel x-ray source that uses bundles of carbon nanotubes. The company is farther along in development, having brought its technology to clinical testing with Siemens. But Enzmann says the advantage of Radius Health's technology is that the panels can be readily fabricated over large areas using methods already employed in the microchip industry.