Siemens’ joint venture focuses on circular x-ray tubes

X-ray tubes that encircle the patient could make mechanical CT systems obsolete in several years, if the hopes of executives at Xintek and Siemens Medical Solutions are realized.

The two firms have agreed to form a joint venture to develop these "multipixel" x-ray tubes, so named because they instantly generate x-rays from multiple points, creating data that otherwise might require rotation of a mechanical CT gantry.

Commercial products could be on the market in a year or so, according to Xintek Chairman Otto Zhou, Ph.D. These first systems, however, will not be installed in medical facilities but in airports, where they will be used to scan baggage. Medical applications could be ready a year or two later.

If installed in a CT scanner, the stationary, donut-shaped x-ray tube would eliminate the need for a mechanically driven imaging chain. This tube would encircle either a conveyor belt carrying baggage or a table holding a patient. These tubes, however, would not be limited to just CT, which collects x-ray data over a full 360°.

"Other devices would collect data over a smaller angular range," Zhou said. "These would be ones that require temporal resolution."

Zhou refused to provide details or describe specific applications. Devices of this type, however, are well known; one performs rotational x-ray angiography. As with CT devices, these would capture data in a fraction of the time now needed, if the prototype x-ray tubes now in development fully pan out.

The joint venture charged with bringing this concept to reality, XinRay Systems, will leverage nanotechnology licensed from the University of North Carolina at Chapel Hill to produce this next generation of x-ray tubes. The prototype of a system employing such a tube, a 25-pixel multiplexing CT scanner, has already been built at UNC as a proof of concept.

Researchers led by Zhou, Lyle Jones distinguished professor of materials sciences and physics at UNC, described the multiplexing CT scanner in a presentation at the American Association of Physicists in Medicine meeting (DI SCAN, 7/20/07, Multiplexing CT scanner heads for center stage at AAPM meeting).

The fundamental concepts underlying this new breed of x-ray tubes have been fleshed out partly through a two-year collaboration between Xintek and Siemens. Xintek is a spin-off from UNC that holds the license to the nanotechnology. Siemens has expertise in refining and manufacturing x-ray tubes.

Both companies are contributing core staff to XinRay Systems, based in Research Triangle Park, NC, near Xintek's offices. Zhou expects the joint venture staff, most of whom are from Siemens laboratories in Germany and China, to ultimately number 15.

Today's x-ray tubes have hardly evolved over the century since Roentgen's discovery of electromagnetic radiation, Zhou told DI SCAN. If multipixel x-ray tubes meet expectations, they will fundamentally change how x-rays are generated and used.

Conventional x-ray tubes produce electrons when metal filament is heated to 1000°C or above. Those electrons bombard metal to generate x-rays. Xintek's nano-based tubes also bombard metal with electrons to generate x-rays, but the electrons are generated with an electrical charge applied at room temperature. This provides the basis for a quantum leap forward in x-ray technology, according to Zhou.

"With current tubes, x-rays are coming off one point in space," he said. "With multipixel technology, the x-rays come out at different points, so you can get all the projection images necessary for CT without any mechanical motion."