Monday, August 3, 2009

Nanotube powerd x-rays

Conventional x-ray machines consist of a long tube with an electron emitter, a tungsten filament, at one end and a metal electrode at the other end. The tungsten filament emits electrons when it is heated to 1000 degree Celsius. The electrons are accelerated along the tube and strike the metal, creating x-rays.

Instead of single tungsten emitter, the University of North California (UNC) team uses an array of vertical carbon nanotubes that serve as hundred of tiny electron guns. While tungsten requires times to warm up, the nanotubes emit electrons from their tips instantly when a voltage is applied to them.

A company called Xintek in Research Triangle Park, NC, to commercialize the technology. Xintek has team with Siemens to form a joint-venture company.

Taking clear, high-resolution x-ray images of body organs is much easier with the new multi-beam x-ray source. Conventional computerized tomography (CT) scan machines take a few minutes to create clear 3-D images using x-ray. Because the radiation is coming from one point in space, the machine has to move the [electron] source and detector around the object. The x-ray emitter fires while the tube moves. The motion of the heart and lungs can blur images, so a CT scanner takes hundreds of pictures that are synthesized to reconstruct a 3-D image. It speeds up organ imaging, takes sharper images, and could increase the accuracy of radiotherapy so it doesn't harm normal tissue.

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