Nano X-ray tube

Material scientists, medical physicists, and cancer biologists will all benefit from the development by US researchers of a low-cost X-ray tube packed with sharp-tipped carbon nanotubes.

Technologists are improving X-ray machines all the time, the device that generates the X-rays by using a vacuum tube to smash high-speed electrons into a piece of metal gets smaller as new approaches to manufacturing are improved and new discoveries in the underlying science made. This allows improved X-ray image resolution, which means greater clarity and detail of X-ray pictures that get right inside the body and see deep inside seemingly solid material.

Now, a team of nanomaterial scientists at the University of North Carolina has revealed a new type of relatively inexpensive and small X-ray device to this year’s meeting of the American Association of Physicists in Medicine in Anaheim, California. The new device will have applications in imaging human breast tissue with potentially unprecedented detail, as well as uses in biomedical research and materials science and engineering. Control that is not possible with conventional X-ray tubes could be made available to a whole range of users.

Otto Zhou, Sha Chang, and their colleagues at UNC have developed a cold X-ray tube to supplant the vacuum tube and the electron-producing hot tungsten filament. They use closely packed carbon nanotubes which emit electrons from their sharp tips when a voltage is applied. These electrons impact a metal target and produce a burst of X-rays.

Otto Zhou
Otto Zhou

The team has already used their nanotubes X-ray source to produce a micro-sized scanner for imaging the internal organs of small laboratory animals. One of the added advantages of the new approach to X-ray production is that the improved clarity avoids the blur caused by a small living creature’s rapid breathing and high heart rate. On conventional X-ray machines slow mechanical shutters are opened and closed to take X-ray snapshots timed to the breath but small animals breathe too quickly for this to work.

Chang and Zhou have demonstrated that their carbon nanotubes, which can be turned on and off instantaneously, are fairly easy to synch up to equipment that monitors small animal’s breathing or heart rate.

The same nanotube devices could improve human cancer imaging and treatment as well as providing more compact X-ray sources for engineering and materials applications that need to reveal internal structural details of small components.

Further reading

51st AAPM Annual Meeting, 28 July 2009

Otto Zhou Research Lab

Author: David Bradley

Award-winning, freelance science writer based in Cambridge, England.