CT vendors ready push for next-generation scanners

Barely three years after the introduction of 64-slice CT, Toshiba America Medical Systems will ask the market at this year's RSNA meeting to embrace scanners capable of 256 slices. Siemens Medical Solutions will introduce a 128-slice scanner just one year after releasing its dual-beam CT. Philips will tout newly upgradable CT scanners, and GE Healthcare will demonstrate image quality enhancements that company executives say will deliver soft-tissue contrast similar to that found with MR.

If all of this seems like a lot, brace yourselves. There's more. Productivity and dose reduction will play loud and clear at each of the major vendors' booths on the RSNA exhibit floor. The slice war that all vendors love to hate will intensify with detector developments showcased for release in the near and long term.

Siemens will leap forward with a 64-row detector, double the size of detectors on both its Sensation 64 and dual-beam Somatom Definition. The company will combine this new 64-row detector with its z-Sharp technique, which turns each slice into two, producing the industry's first 128-slice scanner. The new scanner, the Definition A S (Adaptive Scanning), will include a novel collimator and software to cut dose; protocols to support 4D perfusion imaging of whole organs, such as the brain and liver; and a wide-bore gantry and heavy-duty table to handle obese patients.

In deference to the hit CT has taken in the marketplace from reimbursement cuts, Philips will talk up a value CT family that can be upgraded in the field from six to 16 slices, from low- to high-power generators and tubes at 16, and a 64-slice scanner tailored just for radiology. The company will also look ahead to a "next step" technology beyond 64 slices that will enter the market in 2009.

Toshiba will stand by its earlier promise to release in mid-2008 a commercial version of its 256-slice scanner. But at this year's RSNA meeting, when companies typically showcase the next year's biggest commercial offerings, the company may downplay the 256-slice system, at least a little, to keep from stalling demand for its other products, according to executives. As a result, look for Toshiba to emphasize products at its booth that enhance the operation of its line of Aquilion scanners at 16, 32, and 64 slices.

Getting much of the attention will be a user interface for streamlined workflow and software for increased productivity.

GE also will demonstrate technologies that build on existing ones. Ones that improve image quality and reduce dose will be featured as opposite sides of the same equation. Innovative measures to boost image quality will provide the capital for GE LightSpeed VCT users to trade for decreased patient radiation exposure. The company will also present results from efforts to obtain dual-energy images using only one x-ray source rather than the two built into Siemens' Somatom Definition.

Underpinning these developments-past, present, and future-are the computing engines that make sense of the myriad data streaming into CT consoles. Data overload, an issue since the introduction of quadslice scanners nearly a decade ago, has never been so acute. Vendors on the RSNA exhibit floor will argue they have it under control. That is no easy task.

CTs acquire data in a matter of seconds. Sixty-four-slice scanners may be switched on for only five or six seconds. Siemens' dual-beam Definition may scan for even shorter times, and Toshiba's 256-slice CT for only a few seconds. Simple math provides a hint at the kind of data being delivered.

Today's most advanced CTs produce 64 slices every 330 msec. Algorithms can pare that to 165 msec. Those on Siemens' dual-beam Definition cut temporal resolution to 82.5 msec. Toshiba's 256-slice CT will press computability even further.

"It is imperative that these processes are really automated, because you can be looking at larger volumes of data in advanced studies," said Doug Ryan, senior director of the Toshiba CT business unit.

Advanced applications on the Toshiba 256 involve whole-brain neuro perfusion studies or functional studies of the heart to determine myocardial viability, potentially generating close to or even beyond 10,000 slices. Standard coronary CT angiography studies, however, will likely produce no more, and probably less, data than cardiac scans with a 64-slice scanner, according to Ryan. The reason is that the wide area detector onboard Toshiba's new scanner will make a single rotation around the patient's chest and, consequently, will not have the slice overlap of helical scanners now on the market. Scan time will drop as well.

The beta version of the scanner tested earlier this year at Johns Hopkins University in Baltimore completed its single rotation in 0.5 seconds. The specifications on the commercial version due for release next summer have not yet been determined, pending FDA clearance of the scanner. It will likely have a rotational speed equivalent to or better than the 0.35-second rotation on Toshiba's Aquilion 64, according to Ryan.

Images slated for Toshiba's RSNA booth will show the early results of beta site trials. Among those being considered for display are single rotation scans of the heart and advanced studies involving the brain, as well as dynamic studies of wrists and ankles.

Displays of these images will be accompanied by descriptions of how Toshiba's partnership with Vital Images will translate into applications that will optimize productivity for the 256-slice scanner when it enters the market next year.

"We'll be talking about what we learned from the beta projects on how to handle data and how the workstation will be part of the network," Ryan said.

Siemens Medical Solutions will showcase its own clinical accomplishments achieved with the dual-beam Somatom Definition, which entered the market at the end of 2006. Company execs hope to dazzle booth visitors with images of complex vasculature near the skull and across the knee, distinguished from bone through direct subtraction of data sets created at 80 kV and 140 kV. These images will be complemented by non-contrast-enhanced shots of the liver, lung perfusion defects, cartilage, tendon, and ligaments.

New applications of dual-energy CT may include scanning for pulmonary embolism. Siemens luminaries have found the technique promising for identifying not only the location of a thrombus but perfusion defects. Other possibilities are cancer imaging; therapy monitoring; and determining the effect of anti-angiogenic drugs.

But this year's German pride and joy will be a new member of the CT family, the 128-slice Somatom Definition A S, which Siemens is planning to begin delivering to customers in May 2008. It is so named because the new CT is based primarily on technologies found in the Definition platform. The new scanner, which depends on just one x-ray beam, not the two in its namesake, will be configurable with 20, 32, and 64 detector rows. (The two detectors onboard the Somatom Definition have only 32 detector rows each.)

In combination with z-Sharp technology, which rapidly guides the x-ray beam back and forth to double the number of slices per rotation, the Definition A S will render 40, 64, and 128 slices each time around.

"To be honest, we do not like to continue this slice war too much," said Andre Hartung, vice president of CT and sales for Siemens. "In the end, whatever you do in CT has to translate into a clear benefit."

The Somatom Definition A S takes a position in Siemens' CT portfolio as the company's most versatile single-beam performer, able to handle the most challenging patient with a large- diameter gantry and heavy-duty table, high-power x-ray generator, and wide area detector, augmented by technology for dose reduction and advanced perfusion studies.

To cut dose, Siemens has developed a "tube-side" collimator that trims unnecessary radiation at the beginning and end of each helical scan. Hartung explained that the first 180 degrees turn of the imaging chain of a scan and the last 180 degrees turn do not provide diagnostic data.

"You can avoid this (unnecessary radiation) with a tube-side collimator," he said.

To support advanced studies, Siemens' adaptive spiral scanning allows dynamic imaging of whole organs. This technique, which moves the patient table back and forth, allows coverage up to 26 cm. This counters a problem that has plagued multislice CT scanners since their introduction: the tendency of fast CTs to outrun the contrast bolus.

"Adaptive spiral scanning provides whole-organ coverage of the liver and brain with sufficient temporal resolution for perfusion imaging," Hartung said.

Getting the most from this technology will require optimized perfusion and injection protocols that ensure the bolus, imaging chain, and patient table work as a team.

GE engineers have developed similarly advanced technology for their premium-end LightSpeed VCT. By reducing noise, increasing the number of views, and doing more iterations of data with the reconstruction engine, GE has dramatically improved image quality, said Dom Smith, GE general manager of CT advanced technologies.

"We can get the same image quality with a 200 mA exam that you get from a 400 mA exam," Smith said.

These gains in image quality can provide exceptional contrast resolution or be traded off for lower dose. The trade-offs between image and dose figure into the three themes that GE plans to present at the RSNA meeting:

• See more with technologies that push the boundary of image quality;

• Know more with applications using dual energy and large areas of coverage; and

• Lower dose by trading off increased image quality for less radiation exposure.

Improvements in image quality will come from enhancements in every component of the imaging chain. GE engineers have tweaked the x-ray tube, detector, data acquisition system, and reconstruction software and hardware. The end result is a dramatic improvement in soft-tissue contrast.

"Imagine if you could see a CT image that looks like an MR for soft tissue," Smith said. "We haven't gotten our CT to 3T, but we think it is close."

GE is working on a method for dual-energy CT that he said "we think will be the fastest in the industry." The company is using its single-tube CT to acquire one data set at high energy, 140 kV, and a second at either 80 or 60 kV and then subtracting one from the other. Smith refers to this method as an electronic approach, distinct from Siemens' mechanical approach of using two x-ray tubes.

"We know the electronic approach with double pulse and two acquisitions is fundamentally possible," he said. "We will show clinical proof of that at the RSNA."

The company is also working on spectral CT, involving a change in detector technology that counts photons-a detector without slices, according to Smith. This technology, however, is further from market than any other in the works at GE. Dual-energy could be on the market in 12 months or less. The image quality improvements will be commercialized in 12 to 18 months.

Driven by reimbursement cuts affecting the outpatient market in North America, Philips will introduce new value configurations with upgrade paths to protect investments. The company will also bring advances in workstation technology and applications addressing cardiovascular disease, stroke, and cancer.

"We are going to demonstrate how CT can be used throughout the cycle of care, if it is appropriately integrated," said John Steidley, vice president of Philips global CT marketing.

The value configurations will provide upgrades from six to 16 slices, a 16-slice CT with upgrade from lower to higher power configurations for tube and generator, and a 64-slice scanner with cardiac protocols tailored just for radiology.

Improvements in its standard line of CT scanners, including the 64-slice Brilliance, will boost image quality while reducing dose, according to Steidley. Advances will affect key components of the scanner that affect x-ray generation, data acquisition, and image reconstruction.

Philips will feature technology similar to Siemens' z-Sharp, which gets two slices for each detector row by changing the x-ray beam. This technology will complement a technique developed by Philips that already manipulates the focal spot to improve spatial resolution on its high-end 64-slice scanner, he said.

"With these two, we will get the best of those two worlds, and we have even some future capabilities beyond that," Steidley said.

He only hinted at what the company would actually be unveiling this month in Chicago.

"We'll be showing something bigger than 64," he said.

Visitors to the Philips booth will see it in a few weeks, but they'll have to wait a bit longer to buy it. The "beyond 64" introduction is scheduled for release in 2009.