Lesser slice CTs find niches in and outside of radiology

Vendors have created CT scanners for every price point and clinical need, and medical facilities are snapping them up.

Last year, this plethora of choices led the U.S. market to explode, as shipments of new CTs increased 8%, surpassing $1.3 billion. This year has seen more of the same, as the craze for 64-slice scanners continues, and vendors have expanded their portfolios in decidedly pragmatic ways.

In 2005, Siemens added the entry-level dual-slice Spirit and the 16-slice Emotion. The new systems complement the company's single-slice Spirit; Emotion 6; quad-, 16-, 20-, and 40-slice Sensation CTs; and superpremium Sensation 64 and Sensation Cardiac.

Philips offers its Brilliance CTs in six-, 10-, 16-, and 40-slice configurations, in addition to its 64-slice version and the 16-slice Big Bore scanner dedicated to oncology, which began shipping only a few months ago. Toshiba has the Aquilion 4, 8, 16, 32 and 64, plus the work-in-progress Aquilion LB (large-bore) oncology system. GE's LightSpeed is available in 16-, 32-, and 64-slice configurations, as well as a quadslice version for general purpose and another for oncology, and four distinct single- and dual-slice scanners.

The number of choices facing visitors to the RSNA meeting might seem a bit excessive, given radiologists' predilection for buying the most powerful CT scanner available. Vendors' flagship models have been installed at imaging centers and community hospitals with 50 or fewer beds, as well as sprawling tertiary medicine centers. Atlantic Medical Imaging, which runs five outpatient centers in the Atlantic City, NJ, area exemplifies this tendency to buy the best.

"Our philosophy is never to buy yesterday's technology," said Dr. David Dowe, Atlantic Medical Imaging COO.

This approach may be pervasive, but it goes only so far toward explaining current tastes in imaging, which, despite protests to the contrary, have become remarkably varied. Imaging centers and hospitals have been hanging onto old scanners and buying new ones that are not top of the line. The reason may be the way vendors have tweaked their systems and upgrades to provide greater flexibility and clinical function. In this era of multislice engineering, there isn't much of yesterday's technology.

Three CT vendors introduced scanners generating fewer than 64 slices per rotation this year. Siemens began shipping the Emotion 16 and then added the 40-slice Sensation Open, with a wide-aperture gantry designed for bariatric applications.

Philips' Brilliance CT Big Bore began shipping in early summer, and Toshiba's Aquilion LB was scheduled for release in the fall. Both are 16-slice scanners dedicated to oncology.

GE Healthcare has reengineered its portfolio of lesser slice scanners into state-of-the-art systems with trickle-down technology. The Volara digital data acquisition system and Xtream FX workflow tools, developed for the company's 64-slice LightSpeed VCT, have migrated to the VFX series of LightSpeed 16, Ultra (eight-slice), and Plus (four-slice) scanners.

"It's kind of like 'Intel Inside,' where you are bringing a lot of the technology on the VCT down to these other products," said Bill Radaj, GE's general manager of CT for the Americas.

If it's choices customers want, GE Healthcare provides them. The company offers a 32-channel sidekick to the LightSpeed VCT, as well as two high-power 16-slice scanners, the LightSpeed Pro16 80 and Pro16 100, which complement the lower power LightSpeed 16. The two Pro systems differ primarily in the capacity of their generators and x-ray tubes.

"Anyone looking to do cardiac scanning would consider the Pro scanners versus the base LightSpeed 16," Radaj said.

GE places such emphasis on 16-slice scanners because, despite three years on the market, this class of technology is still the workhorse of CT. Half of all CT sales at Toshiba are Aquilion 16s, according to Doug Ryan, director of Toshiba America's CT business unit. Much of the remainder, about 40% overall, consists of 32- and 64-slice scanners. Only about 10% are quad-, dual-, or single-slice scanners.

Where these lower profile systems fit, how they compare, and the advantages each brings are key to making smart choices. Most single- and dual-slice CTs from Siemens and GE are sold outside radiology to small hospitals or private practices. Typical studies might focus on the sinuses, generating images that are used to plan surgery, or they may look at the inner auditory canal, plumb the renals for kidney stones, or search the abdomen and pelvis for signs of cancer.

Their price endears these systems to nonradiological customers. GE offers its single-slice HiSpeed CTE for $210,000 to $290,000 and its HiSpeed Dual for under $320,000.

"More and more people are looking at these because they are finding that they can preserve some revenue by offering CT right in their offices," Radaj said.

SECOND REVOLUTION

Quadslice scanners launched the multislice revolution seven years ago. Now they are causing a stir because of how far their prices have fallen. Siemens, GE, and Toshiba price their quadslice scanners in the low $400,000s, even though they are equipped with better hardware and software than predecessors that commanded $1 million in 1998.

The clinical reach of these scanners is surprisingly long. Steinberg Diagnostic Medical Imaging in Las Vegas employs four Aquilion quadslice scanners for routine radiological studies: inner ear and musculoskeletal applications, spine imaging with multiplanar reformations of slices 1 mm or thinner, even pulmonary and renal CT angiography.

"For the majority of applications, a four-slice scanner is more than adequate," said radiologist Mark Winkler, a partner in the seven-center imaging chain. "Where the four-slice falls apart is if you are trying to do CTA over a large body segment; for example, if you want to do a peripheral runoff. Then the four-slice doesn't have enough speed."

A half-step up are Philips' Brilliance and Siemens' Emotion six-slice scanners. Siemens characterizes this niche as popular with institutions hesitant to explore advanced applications, such as those in the heart, or facilities that don't have the patient populations requiring such scans.

"Cardiac is the most rigorous application, and for that we would need scanners with higher performance," said David Bradley, director of CT collaborations for Siemens.

At Siemens, that means at least the Sensation 16. The system features a 0.4-second rotation time and a water chiller to cool its Straton advanced x-ray tube. Sensation 16 contrasts with Siemens' other 16-slice product, the Emotion 16, an air-cooled CT with a less powerful x-ray tube designed for routine radiological applications and priced below the Sensation 16.

Siemens accomplishes the upgrade from six to 16 slices with a forklift, but Philips does not. Owners of the six-slice Brilliance CT can field-upgrade to 10 or 16 slices in about a day, according to Richard Nelson, director of global field marketing for Philips. Field engineers can accomplish the upgrade so quickly because the same detector is used in both types of scanner. The driver behind such an upgrade is usually an increasing number of patients or an interest in coronary CTA.

Sixteen-slice scanners can kindle that interest in cardiac applications but cannot satisfy it. That takes a different class of technology: the 32-, 40-, and 64-slice scanners. Atlantic Medical Imaging purchased a 64-slice scanner earlier this year and has ordered a second. But the multimodality, multisite provider has no immediate plans to buy more. The 64-slice scanners will be used for cardiac scanning as needed. Routine radiological applications will be served by three 16-, an eight-, and a four-slice scanner.

"Right now it would be business suicide to have seven 64-slice scanners," Dowe said. "You have to wait for reimbursement."

HEART OF CT SCANNING

Sixty-four-slice scanners tower over competitors in cardiology, as their speed and coverage are specifically suited for assessing the most dynamic organ in the body. Philips insists, however, that its 40-slice scanner does a more than acceptable job on cardiac applications.

"It gives you a cardiac exam in under 10 seconds and the smallest voxel in the industry: 0.33 x 0.33 x 0.34 mm," Nelson said.

Philips' 64-slice scanner delivers the same size voxel but larger coverage and faster rotational speed. These translate into five-second cardiac exams. The customers who buy into cardiac applications with a 40-slice Brilliance scanner can upgrade to the 64-slice configuration in the field by swapping out the detector module, upgrading the software, and recalibrating the system, he said.

The cost of acquiring either system or upgrading from 40 to 64 slices varies according to circumstances, Nelson said, though he offered no details about pricing.

Toshiba's Ryan was more forthcoming: Toshiba's 32-slice Aquilion, which puts customers in the rarified zone of cardiac performance, does so at a discount price of around $1.2 million, versus $1.4 million for the 64-slice version. Because the scanner has the same detector as its big brother, field upgrades are a snap, he said. Add 32 channels, some processing boards, and advanced software, and you have an Aquilion 64.

GE can field-upgrade its 32-channel customers as well, but it requires a detector swap, along with boards that increase the number of channels to 64.

Toshiba has made a point of not penalizing customers for choosing the lesser of two great powers, Ryan said. The difference between the 32- and 64-slice Aquilion-about $200,000-is the same as the cost of upgrading from one to the other. But what's more surprising than Toshiba's bend-over-backward deal for customers is that the company doesn't get many takers.

Since its release of the Aquilion 64 earlier this year, Toshiba has sold relatively few Aquilion 32s. Most have been part of large package deals, such as to government agencies that want to buy as much equipment as possible up front and then budget for upgrades later on.

In the majority of cases when 64-slice scanners are chosen, marketing, rather than medicine, takes control.

"I think most people tend to choose the most expensive product they can manage to acquire for fear of being left in a disadvantageous marketing position," Winkler said. "It is not the most logical decision, but it is the one a lot of people seem to be making. Many people are buying 64-slice systems who really have little need for them."

MAKING LOGICAL CHOICES

The latest breed of multislice CTs designed for oncology makes a lot of medical sense. Sasa Mutic, an associate professor of radiation oncology at Washington University in St. Louis, outlined three reasons multislice CT simulators, such as Philips' Brilliance Big Bore 16-slice scanner, are the hands-down winners in any competition with traditional single-slice CT units. The first is image resolution.

CT images are the basis for digitally reconstructed radiographs, which serve as the building blocks for virtual patient models. The thinner the slice, the more accurate the models, Mutic said. Single-slice simulators typically produce slices from 1.5 to 5 mm. The Brilliance Big Bore delivers submillimeter slices.

The second reason is tube heat. Single-slice scanners seldom produce more than 100 images, although many more may be needed to best define a tumor. Sixteen-slice scanners easily produce 800 thin slices without excessive tube heating.

Third, multislice CT simulators can characterize moving tumors, such as those in the lung, better than single-slice units. Subsecond rotation allows dynamic imaging, which can be used to quantify the extent of tumor motion. This contributes to more accurate therapy planning and results in better targeting and less collateral radiation to healthy tissues.

"With the introduction of multislice CT in radiation therapy, there has been this boom in 4D CT similar to what cardiologists want to do with their patients," said Mutic, who has been using a 16-slice Brilliance Big Bore CT at Washington University since February.

The wide-gantry system will have head-to-head competition when Toshiba introduces its Aquilion LB later this year. Siemens Sensation Open, designed primarily for imaging patients too large to fit in standard gantries, can address this niche as well, according to Bradley. GE Healthcare, the first company to recognize the need for a multislice CT simulator two years ago, continues to offer a quad-slice version, the LightSpeed RT.

Choices are sure to keep increasing as vendors explore new ground. The current best of the best 64-slice scanners will be replaced in due time by even more powerful scanners. It is part of the natural evolution, according to Ryan, who noted that the next generation of postprocessing algorithms has been tested successively on earlier generation hardware.

"We used four slice to develop our thin-slice isotropic imaging. We then used the 16 slice to develop cardiac algorithms that have become routine on the 64," he said. "We are now using the 64 to test algorithms for myocardial perfusion, which will be standard on another machine sometime in the future."

The next generation of megaslicers may be just over the horizon, but for the time being, imagers can look forward to a break from the relentless pace of scanner progress. Vendors are focusing on software to make better sense of the data streaming from the current batch of premium products, Ryan said. And that should keep them busy for at least a while.

Greg Freiherr is business editor of Diagnostic Imaging.