Teeny-tiny X-ray vision

Jul 28, 2009

The tubes that power X-ray machines are shrinking, improving the clarity and detail of their Superman-like vision. A team of nanomaterial scientists, medical physicists, and cancer biologists at the University of North Carolina has developed new lower-cost X-ray tubes packed with sharp-tipped carbon nanotubes for cancer research and treatment.

The tiny technology, presented at this year's meeting of the American Association of Physicists in Medicine in Anaheim, California, is being developed to image human , laboratory animals, and patients under radiotherapy treatment, and to irradiate cells with more control than previously possible with conventional X-ray tubes.

The X-ray machine used in a typical hospital today is powered by a "hot" vacuum tube that dates back to the beginning of the 20th century. Inside the tube, a metal filament -- similar to the one that creates light in an incandescent bulb -- is heated to a temperature of 1,000 degrees Celsius. The heat releases electrons, which accelerate in the X-ray tube and strike a piece of metal, the anode, creating X-rays.

Sha Chang, Otto Zhou, and colleagues that University of North Carolina have developed cold X-ray tubes that replace the tungsten filament with carbon nanotubes packed like blades of tiny grass. Electrons are instantly emitted from the sharp tips of the nanotubes when a voltage is applied. "Think of each nanotube as a lightning rod on top of a building. The high electric field at the tip of the lightning rod draws the electric current from the cloud. Carbon nanotubes emit electrons using a similar principle," said Chang.

The group used the nanotubes to build micro-sized scanners and image the interior anatomy of small laboratory animals. Existing X-ray technologies have difficulty compensating for the blur caused by the creature's breathing. Slow mechanical shutters that open and close to block and release the radiation are used to time X-ray pulses to correspond with breath, but their speed is inadequate for small animals because of the creatures' extremely fast breathing and cardiac motion. 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 nanotube devices may also improve human cancer imaging and treatment. CT scanners currently in use check for breast cancer by swinging a single large X-ray source around the target to take a thousand pictures over the course of minutes. Using many nanotube X-ray sources lined up in an array instead, breast imaging can be done within few seconds by electronically turning on and off each of the X-ray sources without any physical motion. This fast "tomosynthesis" imaging improves patient comfort and boosts image quality by reducing motion blur. Using 25 simultaneous beams, the team produced images of growths in breast tissue at nearly twice the resolution of commercial scanners on the market.

This summer Chang's team will conduct a clinical test of a first generation nanotube-based imaging system for high-speed image-guided radiotherapy. The research image system is developed by Siemens and Xinray Inc., a joint venture between Siemens and a University of North Carolina startup company Xintech Inc.

Source: American Institute of Physics

Explore further: Materials for the next generation of electronics and photovoltaics

add to favorites email to friend print save as pdf

Related Stories

New X-ray device using carbon nanotubes

May 12, 2005

Scientists at the University of North Carolina at Chapel Hill and a UNC start-up company, Xintek, Inc., have invented a new X-ray device based on carbon nanotubes that emits a scanning X-ray beam composed of multiple ...

Space saving approach to satellite communications

Dec 05, 2005

Ken Teo and his team at the University of Cambridge have come up with a much more efficient and compact way to send signals from satellites. They have managed to use an array of carbon nanotubes to create a ...

New tool for early diagnosis of breast cancer

Sep 17, 2008

Scientists from Finland, Germany and the ESRF have developed a new X-ray technique for the early detection of breast cancer. This allows 3D visualization of the breast with a high spatial resolution and is ...

Recommended for you

Energy storage of the future

Oct 20, 2014

Personal electronics such as cell phones and laptops could get a boost from some of the lightest materials in the world.

User comments : 0