Mayo Clinic in Rochester, Minn., and NYU Medical Center (NYUMC) in New York City are the first facilities in the U.S. to install Siemens SOMATOM Definition, the company's dual-source computed tomography (CT) system. The system incorporates two x-ray sources and two detectors in a single scanner. Siemens is projecting it will install over 150 Definitions by year’s end. To date, 10 Definition scanners have been installed worldwide, the company said.

The new U.S. installs are making use of the system for cardiac and vascular exams, as well as research into new applications for CT imaging. Mayo Clinic has already begun research studies exploring the system's potential in using dual x-ray energies to better differentiate tissue in various parts of the body.

The SOMATOM Definition has the ability to capture data twice as fast as any existing multidetector CT technology, and can deliver motion-free cardiac images, independent of heart rate, according to Siemens. The Definition also has power reserve and dual-energy capabilities not previously available with any other CT system, providing new uses in emergency radiology.

At Mayo Clinic and NYUMC, the systems are being used to perform cardiac exams on patients with heart rates of 100 beats per minute and more without the need to slow a patient's heart via medications, as was required with previous CT systems. Also, the technology used in the Definition is designed to provide maximum performance in terms of both spatial resolution and temporal resolution.

The Definition also is designed to overcome the limitations often experienced when scanning obese patients with single-source CT systems. Its two x-ray sources provide physicians with increased power to obtain richly detailed images of these patients, while the system's speed limits radiation exposure. In addition, the Definition has a wide bore opening of 31 inches to ensure comfortable scanning of larger or claustrophobic patients, Siemens said.

Use of the system has shown some of its potential applications, such as to help differentiate and isolate tissues. Researchers at the Mayo Clinic have begun exploring the feasibility of using two different x-ray energies for a number of potential applications.
The next U.S. installations of the SOMATOM Definition are under way at William Beaumont Hospital in  Royal Oak, Mich., and The Cleveland Clinic Foundation in Ohio.