GE Healthcare unveils CT scanner sporting 64 detector rows

Execs frame LightSpeed VCT as first true volumetric CT

One of the four vendors of multidetector CTs has dropped the final shoe. GE Healthcare is introducing the LightSpeed VCT (Volume CT), a 64-slice volumetric scanner.

Dressed out with 64 rows of detectors spanning twice the width of the company's current LightSpeed Pro 16 scanner, the VCT will capture any static organ in a second; scan a patient from head to toe in five seconds; and capture the heart and coronaries with prospective gating in fewer than five heartbeats.

Having received FDA clearance to market the product just a few weeks ago, GE Healthcare began talking up the system in early March at the European Congress of Radiology in Vienna and at the American College of Cardiology meeting in New Orleans, showing phantom image work but not the hardware. That will come later. VCTs are only now being prepared for installation at clinical sites. Sales to early adopters will begin by the end of summer, and production and routine deliveries should be in full swing by the end of the year.

"There are a lot of customers with long-lead buying cycles making their product planning decisions for the end of this year and early next year," said Scott Schubert, global product manager for CT at GE Healthcare. "We wanted them to know our technology development plans and at what point the VCT will be ready for commercial availability."

LightSpeed VCT will address many of the questions now being answered by the 16-slice LightSpeed in trauma, neuro, angiography, pulmonary, and cardiac applications. The extended coverage, however, will quicken scans in each of these areas. The VCT promises to be especially helpful in cardiovascular studies in freezing the cardiovascular system.

"Imaging of the coronaries will be the biggest application area," Schubert said. "VCT will provide the ability to image them at submillimeter resolution."

This requires more speed than 16-slice scanners can muster to avoid motion artifact. The coronaries move four to five times the diameter of the lumen with each heartbeat, and 16-slice scanners must average the coronaries over 15 to 20 beats-too many to achieve high-resolution images. Cutting that number of beats to four or five does the trick, and VCT can do that.

GE is framing the LightSpeed VCT as the imaging community's first true volumetric scanner, because it acquires and presents data in 3D. The scanner offers 0.625-mm resolution across 64 slices spanning the 40-cm width of the detector.

This performance is achieved partly with a new generation of detector technology that incorporates advanced signal processing electronics and an enhanced form of the HiLight ceramics incorporated into GE's CT detectors for the better part of a decade. Both came out of GE's Global Research Center in Schenectady, NY, where engineers boosted performance by tweaking light output and afterglow, and designed application-specific integrated circuits with the power to keep up with the new detector.

LightSpeed VCT has been designed for upgradability as well as high performance, according to Peter Arduini, general manager of functional and CT imaging at GE Healthcare. This is something of a novel concept in multidetector CT. When MDCTs were introduced six years ago, vendors said optimistically that they might be upgraded in the field by swapping outdated detectors for new ones. But practical issues surrounding such swaps, the addition of data acquisition systems, and their calibration led vendors to exchange new, more powerful CTs for old ones. GE hopes to downplay that approach with the VCT.

"We would like to get away from the last few years when forklifts were needed to upgrade systems by building as much upgradability into the VCT as possible," Arduini said.

To do this, some of the components built into the VCT will exceed the performance requirements of the scanners as they are originally configured. For example, LightSpeed VCT will ship initially with a 400-msec rotational speed. The mechanism needed to bump that speed to 300 msec, however, will be built into these products. Owners will not be able to access this capability until the faster rotational speed is rigorously tested and its value proven. Once that happens, GE plans to be able to upgrade customers to a faster rotational speed with relative ease in the field.

GE is also employing components already proven on preceding models. The volumetric scanner will be using the Performix Pro X-ray tube, which is currently built into the LightSpeed Pro 16. The tube was engineered to deliver more than enough power for 64-slice scanning, according to Arduini, and to tolerate increased rotational speeds as fast as 300 msec.

Another proven technology onboard the VCT is GE's scalable Xtream data management system, introduced last year on the LightSpeed Pro 16. Xtream provides the workflow solutions and soft-copy reading tools needed to take advantage of VCT's increased speed.

"By not changing all the components simultaneously, we can minimize the strain and risk being built into the design of the system," Arduini said.

While several critical subsystems remain fundamentally true to preceding designs, they are nonetheless being seeded with elements providing improved performance. Xtream, for example, will have productivity tools for handling the enormous quantity of data being generated by the VCT: Reconstruction filters for presenting slices at different thicknesses provide different levels of noise and image quality, and different reformatting tools present the data the way the physician wants to see them.

"All that will be built in, up front," Arduini said. "All the volumetric reconstructions will be there: all the sagittal, coronal, and oblique reformats. The images will be automatically routed to the filmer and PACS at the appropriate slice thickness and resolution."

LightSpeed VCT will expose patients to less radiation dose than its 16-slice predecessor, when comparing scans of the same body part. One reason, Schubert explained, has to do with the width of the new detector.

"There is wasted dose, called overbeaming, which spreads over the side of four-, eight- or 16-row detectors," he said. "Because the 64-row detector is wider, it has less overbeaming and is more efficient."

LightSpeed VCT is a fundamentally different scanner from what has come before, said GE executives, who hope this new scanner will lift the company out of the slice rut into which the industry has fallen. For the past six years, CT vendors, including GE, have defined their scanners by the number of slices they generate per rotation. Some in the imaging community have sought to redefine this genre as multidetector CTs. These terms, once illuminating, now could be confounding.

While Toshiba's latest 32-slice Aquilion is in line with its number of detector rows, Siemens' high-end Sensation is being described as generating 64 slices but needing only 32 detector rows to do so.

GE is seeking to set the VCT apart by framing its latest development as a volumetric scanner, hoping to divert the focus from performance specifications to clinical value. The company is fighting an uphill battle, however, in the absence of clinical data, which will come only after sites begin scanning patients and luminaries begin publishing papers. Even then, it could be many months before those ideas are widely accepted. In the meantime, company execs will be asked how many detector rows are recording how many slices-and the slice wars that have characterized CT since the late 1990s will continue.