Siemens takes high ground in CT with fast gantry, better software

Rotation sets new industry benchmark at 0.37 second

CT just got faster and safer. Siemens Medical Solutions has developed x-ray tube technology that allows faster gantry rotation and tube cooling, optimized data reconstruction algorithms, and automated x-ray dose calculations. The improvements are part of Siemens' new Speed4D offering, which will be formally launched as part of the company's Sensation 16 product line Nov. 9 to 12 at the American Heart Association annual meeting in Orlando, FL, and Nov. 30 to Dec. 5 at the RSNA meeting.

Systems equipped with Speed4D are in production and will begin shipping early next year, according to Bernd Ohnesorge, Ph.D., vice president of worldwide marketing for Siemens' CT division. Systems with the improved x-ray tube are already shipping. The availability of these enhancements should boost the price of Siemens' Sensation scanners, which has dipped along with other premium CTs in recent months below the million-dollar mark. Premium CT scanners have traditionally sold for around $1.1 million to $1.2 million.

"We have seen rapid drops in prices, but we believe this will stabilize those prices at higher levels," Ohnesorge said. "With this improvement in technology, we are providing the customer more performance for the amount of money that is perceived as the standard for a cutting-edge machine."

Speed4D is already operating at about 20 sites, where Siemens and its customers have been evaluating the new technology. Five are in the U.S. Most applications have been in cardiology, where the advanced tube technology, fast gantry rotation, and reconstruction software have combined to allow not only static but dynamic volumetric reconstructions. The technology has other applications, particularly in trauma.

"In whole-body scanning, it increases the volume coverage and particularly reduces breath-hold time as it improves temporal resolution," Ohnesorge said. "It can cover the entire chest at highest resolution in as few as six seconds."

Vendors have been steadily chipping away at the rotational speed of CT, which dropped from 0.75 second, when quadslice scanners were introduced five years ago, to 0.4 second a year ago, a milestone Toshiba first achieved with its Aquilion-class scanner.

The problem that has stood in the way of even faster speeds has not been the mechanical systems that spin the gantry so much as the ability of x-ray tubes to withstand the gravitational forces exerted on them. Compact design helps make Siemens' Straton tube robust enough for the company to take the next step in speed, allowing 0.37-second gantry rotation.

The new tube design has other advantages as well. Locating the bearings outside the vacuum allows the anode to be directly cooled, sloughing off 5 million heat units per minute. Even at maximum load, the tube cools faster than the time to the next procedure, according to the company, contributing to increased throughput. The compact design also supports a longer life compared with other CT tubes, Ohnesorge said.

Automated reconstruction allows complex data sets to be processed rapidly. The Workstream4D software optimizes data reconstruction to achieve speeds up to 10 images per second in real-time mode and up to five per second in full conebeam imaging. Data from up to 24 phases of the cardiac cycle can be assimilated in minutes. Workstream4D also helps radiologists deal with data overload. Direct 3D reconstruction, using a predefined series of image planes, captures all the data obtained in as many as 2000 slices, according to Ohnesorge.

The final piece to Siemens' new CT puzzle is CARE Dose4D, an enhanced version of the Combined Applications to Reduce Exposure package residing on the company's high-end CT scanners for several years. The upgraded version analyzes the cross-sectional anatomy of patients in real-time and adjusts the x-ray dose to balance image quality and dose for different body densities in the head, chest, abdomen, and extremities. Initial clinical experience with CARE Dose4D has achieved a 66% dose savings.

These components together have created a synergy that promotes image quality, minimizes patient dose, and extends clinical use to the most demanding applications, according to Ohnesorge.

"We believe that just adding more slices at this time doesn't make sense without looking for advances in workflow and tube technology that help better manage the data," he said. "We believe that this technology is the basis and prerequisite for moving forward."