In a breakthrough that may revolutionize radiotherapy and airport baggage scanners, scientists have successfully generated X-rays using carbon nanotubes.
The new method could allow real-time three-dimensional scanning.
"If you look at current imaging technology, technically very little has changed since Wilhelm Rontgen discovered X-rays more than 100 years ago," said Otto Zhou, a materials scientist at the University of North Carolina (UNC) in Chapel Hill.
"It didn't take long to show that nanotubes could generate X-rays in principle. What has taken time is turning this idea into a viable technology," said Zhou.
In conventional X-ray systems, electrons are released from a heated tungsten filament and accelerated down a tube until they strike a metal target, creating X-rays. Because X-rays are fired from a single source, 3D imaging, such as computed tomography (CT) scanning, is particularly cumbersome.
Zhou's 3D scanner uses a series of nanotubes instead of tungsten filament.
Each nanotube emits electrons when a voltage is applied, through a quantum effect called field emission-the electric field becomes concentrated around the nanotube's tip, amplifying the field's effect and making it relatively easy to generate electrons.
However, such a system is considered suitable for real-time 3D scanning because of the speed at which individual nanotubes can be switched on or off.
This can be done within microseconds by applying or removing this voltage.
The new device has many nanotubes positioned around the subject in a 3D array and are activated in sequence, generating a ripple of X-rays that sweeps around the body.
"Electronic switching can create a scanning beam without requiring any mechanical motion of the apparatus," he said.
This scanning technology is fast enough to provide real-time 3D imaging, which will help improve tumour targeting in radiotherapy treatments, said a team member.
The researchers have already shown that high-speed nanotube imaging also reduces the blurring that can be caused by breathing or heartbeats.
Peter Schardt, a medical imaging expert at electronics company Siemens, has said that the technology will also be practical to implement.
"The nanotubes will cost more than conventional X-ray tubes, but it's a trade-off because there will be great savings in the mechanical costs currently required for CT scanners. In two or three years we could be seeing carbon-nanotube scanners that cost about the same amount as today's CT scanners, but have a much higher resolution and lower maintenance costs," he said.
George Zarur, science adviser to the US Department of Homeland Security in Washington DC, said that the technique could speed up airport baggage checks.
"I think this will revolutionize the CT industry," he said.