Nanotube x-rays used to acquire CT images faster
Researchers at the University of North Carolina at Chapel Hill have developed a new way to acquire CT images making use of carbon nanotube x-rays rather than traditional scanners which use less peak power, according to a release of the findings.
The objective behind this work is to further development of scanners for use in not only medical imaging but also homeland security, according to Otto Zhou, PhD, professor of Materials Science, in the curriculum in applied and materials sciences and the department of physics and astronomy, in UNC's College of Arts and Sciences.

"The current CT scanners take images sequentially, which is slow and inefficient. Using the nanotube x-ray technology, we show in this paper the feasibility of multiplexing -- taking multiple images at the same time," Zhou said.

Carbon nanotubes, made of layers of carbon atoms, are being used by the UNC team because they can emit electrons without high heat.

In 2005, Zhou and colleagues created a scanner with multiple x-ray sources, called a multipixel scanner, capable of taking an image of the object from a different angle in fast succession. The latest system combines this multiple-x-ray-source innovation with a principle called multiplexing, in which all the x-ray sources are turned on simultaneously to capture images from multiple views at once.

"Let's take a simple case where suppose you need 10 images," Zhou said. "Let's say each view takes one second. In the conventional step-and-shoot method used for the current CT scanners, you take one shot, and the first pixel stays on for one second. Then we turn on the second pixel, and that stays on for one second." The whole process would take 10 seconds, he added.

"With multiplexing, we can have all the x-ray pixels on at the same time for maybe two seconds. You still get all the images, only faster, and we need only about half of the original x-ray peak power," Zhou said.

Multiplexing is currently used in cellular phones; as cell phone signals travel along the same frequency band, they are eventually divided into separate coherent messages at their destinations, according to the release.

"What makes the multiplexing CT scanning possible is the novel multi-pixel x-ray source we developed and the ability to program each x-ray pixel electronically," Zhou said.

For this recent study, Zhou and colleagues took images of a computer circuit board using a prototype multiplexing scanner, which were then compared to conventional methods. The image quality was identical, but the acquisition time was shortened.

"For this paper we built a prototype or demonstration scanner that gives a limited number of views, to image a simple object," Zhou said. "Our next step is to develop a small CT scanner for small animal imaging."

These developments will be published in an upcoming edition of the Applied Physics Letters journal. The work was funded by the National Cancer Institute (through the Carolina Center of Cancer Nanotechnology Excellence) and the National Institute of Biomedical Imaging and Bioengineering (both part of the National Institutes of Health); the Transportation Security Administration; and Xintek Inc.