Siemens dual-source CT breaks with slice wars

Siemens is radically changing the direction of its CT program with the introduction of its Somatom Definition. The new scanner, publicly announced Nov. 17 and featured Sunday at the RSNA meeting, packs two imaging chains in a single unit, generating 128 slices per rotation. But Siemens is downplaying the number of slices in favor of the speed of the scanner and how its use might change the clinical application of CT.

Siemens has broken with seven years of slice wars, mounting two detectors at a 90-degree angle, each containing 32 elements and aligned with its own Straton x-ray tube, to create a system with extraordinary speed. The Somatom Definition generates a slice in 83 msec - half the time of a conventional 64-slice scanner and fast enough to freeze any beating heart, according to the company.

Conventional single-source scanners acquire a slice after a 180-degree rotation. With two imaging chains, mounted at a right angle to each other, the same information can be acquired with only a 90-degree turn.

It may seem counterintuitive, but the dual-source CT actually cuts dose rather than adds to it. The reason, according to the company, is that scan time is minimized. When applied to the heart, enough data might be acquired in a beat or two rather than the five or more required by current scanners. X-ray exposure to the patient is expected to drop by half.

This power will not come cheap. Customers will pay between $2.3 million and $2.5 million for a Somatom Definition. The price is justified, according to the company, because the speed of the system will eliminate motion artifact when imaging the heart, making it the logical choice for cardiology applications, especially when performing coronary CTA.

The Somatom Definition may also be valuable in acute care. The scanner might be able to handle a broad range of applications, from trauma to the assessment of patients with chest or abdominal pain, according to the company. It might also be applied in virtual colonography and pulmonary imaging.