CT with Nanotubes for People and Baggage ScansFebruary 2nd, 2010 in Nanotechnology / Nanophysics
Researchers from Siemens are investigating the use of small, fast X-ray sources based on nanotubes.
In combination with a computer tomograph (CT) scanner, these could serve to generate high-quality images of rapid processes within the human body, such as the dispersion of a contrast medium. The radiation would be reduced without any sacrifice of image quality compared to the equipment in use today. The use of fast X-ray sources is also attractive for applications requiring a fast throughput. These include scanning systems for luggage and passengers in airports. Siemens is developing these sources together with the U.S. company Xintek in a joint venture by the name of XinRay Systems.
X-rays are generated when accelerated electrons strike an electrode. Today's conventional source for such electrons is a hot filament inside a vacuum tube. However, this type of system consumes a lot of energy, is reacts relatively slow, gets hot, and can only be miniaturized to a certain degree. Therefore, researchers look for "cold" electron sources which emit electrons under high voltage from a metal formed into tiny spikes or sharp edges.
Nanotubes made of carbon are ideal as so-called field emitters, since they are as conductive as metal and also very thin, with a diameter of a few nanometers. They can be activated in less than a millionth of a second, whereas it takes several hundredths of a second to trigger a conventional X-ray source. The researchers at Siemens, Xintek and XinRay first apply nanotubes to a metal substrate and then control these individually in order to create an array of mini electron sources. The technology stems from research by a team at the University of North Carolina and is now being developed into a commercial solution by Siemens.
In the most powerful CT scanners currently available from Siemens, two X-ray tubes revolve around the patient at more than three times per second. In the future, hundreds of mini X-ray sources could be permanently installed in a fixed circle and triggered in sequence. This would generate ten high-quality images per second — fast enough to enable observation of processes such as the destruction of tumor tissue during radiation therapy. It will take several years before such X-ray sources can be used in series-produced medical devices. However, their market readiness for use in industrial environments or to scan baggage in airports could come much sooner.
"CT with Nanotubes for People and Baggage Scans." February 2nd, 2010. http://phys.org/news/2010-02-ct-nanotubes-people-baggage-scans.html