Nanotube Diagnostic X-Rays

The design of the x-ray sources used in many medical and dental diagnostics hasn't changed much in a hundred years. A cathode heats up to 1500 C and then emits lots of electrons, which are pulled across a vacuum tube toward a target where the ensuing impact kicks up a beam of x rays. Now a team of physicists and doctors at the University of North Carolina and the nearby firm of Applied Nanotechnologies, Inc. have created, for the first time, an x-ray source using a room-temperature array of carbon nanotubes to create the electrons and deliver a sufficient x-ray flux for doing practical medical imaging (see figure). The device is much smaller and cooler and the old models, and the resultant x-ray pulse is more focused. Also response time is sharper and the pulse shape can be programmed, which helps in the tracking of moving objects. (Yue et al., Applied Physics Letters, 8 July 2002; contact Otto Zhou, 919-962-3297, zhou@physics.unc.edu.)