Stanford CT meeting underscores potential, pitfalls of next generation

As Stanford's International Symposium on Multidetector-Row CT, began June 23, only a few sites around the world had any experience with CT scanners generating more than 16 slices per rotation. But representatives from those luminary sites were there and they presented whatever they could. Their presentations, underscored by the rapidly accumulating experience with 16-slice scanners, were enough to demonstrate that the real challenge regarding the use of the megaslice systems about to enter the market will have less what to do with the scanners themselves than with handling the data they produce.

Luminaries reported that the 40- and 64-slice scanners produce data sets with from 2100 to 3000 images per exam, an amount of information well beyond the reach of conventional means of interpretation, such as scrolling through slices. Other techniques will be needed, including volume visualization, data segmentation, and CAD. Speakers raised concerns that the current viewing stations and workstations are not equipped to handle the data that will come off these new scanners-and that this lack will limit utilization of the new systems.

Underscoring the importance of this issue was a three-hour session in which presenters, using 3D workstations made by GE, Philips, Siemens, TeraRecon, and Vital Images, interactively interpreted data. The standing room-only crowd watched as each workstation was put through its paces on a series of five cases-some easy, some complex. Physicians manipulated 3D data sets, explaining their work and findings as they went along.

Like the workstation presentation, much of the conference focused on data obtained with 16-slice scanners by examining mainstream CT applications, including chest, musculoskeletal, pediatrics, neuro, and emergency. Attesting to the potential of even 16-slice scanners to contribute to fields beyond radiology was a day-long series of presentations focusing on cardiovascular applications. Workflow, screening, and dose issues were also addressed in separate presentations.

The character of next year's meeting could be markedly different, as it will follow the clinical introduction of yet another generation of CT scanners. At the symposium, Philips executives said they expect to begin commercial delivery of their 40-slice Brilliance in October and projected that 70 such scanners would be installed by year's end. Six are already installed at luminary sites around the world and another half dozen are scheduled to begin operating by September.

GE, Toshiba, and Siemens also have luminary sites operating and are planning commercial releases in the fall and winter. GE will bring its LightSpeed VCT with V-Res Detector and Performix Pro tube, featuring a 64-row detector delivering 64 slices at a rotation speed of 400 msec. The scanner will deliver 40-mm resolution utilizing 0.625-mm slice widths. The first beta version of the system was installed last month at Froedtert Hospital in Milwaukee.

A 64-slice beta version of Toshiba's Aquilion CT is currently being tested at Fujita Health University in Japan. The company plans to commercially release this system in 2005. Before then, customers will be able to purchase a system with 32 channels that can be upgraded later to 64. Common to the two configurations will be Toshiba's Quantum 64-row detector, which delivers slice thickness of 0.5 mm with a gantry rotation speed of 0.4 sec.

Siemens has one 64-slice Somatom operating at the University of Erlangen in Germany. Within weeks, others will be shipped to sites in the U.S., including the Mayo Clinic at Rochester, MN; Cleveland Clinic; the University of California, Los Angeles; New York University; Johns Hopkins University; and the Medical University of South Carolina. The system will be available in two configurations. Sensation Cardiac 64, a dedicated cardiovascular system, will come standard with calcium scoring, vessel view, and an Argus heart-function tool, Speed4D workflow package, and 330-msec rotation. These are options on the general-purpose Sensation 64, which has a standard gantry speed of 370 msec.

Utilizing a flying focal spot, the 32-row detector can produce a detailed scan of the chest in 20 seconds, delivering 64 slices per rotation. At the accelerated speed possible with the dedicated cardiovascular system, the Sensation Cardiac 64 generates 200 slices per second with a temporal resolution as short as 83 msec, which is achieved by mathematically recalculating data obtained during ECG gating. At a standard gantry speed of 370 msec, the Sensation 64 can achieve a temporal resolution as short as 94 msec.

Aside from cardiac applications, the new scanners might be able to differentiate soft and hard plaques. Siemens executives believe their Sensation 64 will be able to sort plaques into three categories based on their Hounsfield qualities: calcified, fibrous calcified, and noncalcified types. This differentiation is possible with intravascular ultrasound but not with coronary angiography, which can determine only the degree of stenosis and not how likely it is the plaque will rupture and create a thrombus that blocks blood flow.

An ability to evaluate factors other than stenosis could permit the use of this new breed of scanner as a noninvasive alternative to diagnostic coronary angiography, freeing cath labs to do interventions and stent therapy.