CT vendors focus on cutting dose, extending clinical apps

November 2, 2009

Impact on patient safety, hospital stay lead list of vendor priorities for scanner enhancements.

The CT world has turned from slice mode to dice mode. Clinical value, derived from voxels and the x-ray dose needed to make them, will be the metrics by which products are assessed at the upcoming RSNA meeting.
    The makers of CTs will bring their most sophisticated arguments ever to Chicago, talking up clinical capability and low dose. The slice wars have ended in a stalemate, as each vendor’s best technology has advanced to the point where anyone’s scanners can do anything radiology or cardiology needs. In the interim, the U.S. market for these systems has collapsed. Revenue from the sales of new units is half what it was just a few years ago.
    What used to drive sales, the introduction of new superpremium models, can no longer do so. New scanners have advanced past the performance that every user needs and to price points that only a few can afford.
    Aquilion One from Toshiba America Medical Systems goes for about $2.5 million, a sticker price the company is maintaining despite the current down economic market. When introducing its new flagship a couple of years back, Toshiba emphasized coronary and brain scanning as the applications best suited to the wide-area detector that serves as the scanner’s cornerstone. These benefits accrue from the detector’s 16-cm coverage, which can capture whole organs in a single subsecond rotation. The company is now focusing on these applications and others that can impact patient length-of-stay in hospitals, a message its executives will bring to RSNA 2009.
    “Anything we can do to paint a bigger picture for physicians to make a recommendation on the patient today is probably the most important thing we can do,” said Doug Ryan, senior director of the CT business unit for Toshiba America Medical Systems.
    Brain perfusion, chest pain triage, and myocardial perfusion studies present the best match for the Aquilion One because of their complexity. But Toshiba will also argue the case for using the Aquilion One as the cornerstone for imaging in the emergency department, as the scanner is well suited to very rapid pediatric and general body imaging.
    Superpremium CTs built by Philips and Siemens are being positioned in much the same way. Siemens has developed a CT Neuro Engine to assess stroke. The Neuro Engine processes data acquired using a volume perfusion technique. Such advanced applications can run on scanners with fewer slices, although they are best suited to superpremium ones that generate 256 slices per rotation and up.
    The Philips Brilliance iCT now running at Fletcher Allen Health Care at the University of Vermont in Burlington, is being used in brain perfusion and neuro CTA, as well as routine body imaging, bariatric, and cardiovascular imaging. But the scanner is only the company’s 100th such installation since unveiling the product at RSNA 2007. At press time, Siemens had placed just 50 of its dual-source Definition Flash, launched at RSNA 2008, and is hoping to reach 100 installations by year’s end. The problem is not clinical reach but the depth of customers’ pockets.
    Superpremium CTs carry superpremium prices, which limit their appeal even under the best economic conditions. Such stratospheric sticker prices are an anomaly if viewed over the history of CT, when newly introduced flagship products led the market to increasingly loftier sales peaks. For the majority of today’s buyers, scanners with 64 or fewer slices can meet most of their needs.
    A miniboom in 16-slice scanners has resulted, playing into the hands of Hitachi Medical Systems America, which has focused its attention on the development of cost-effective, high-performance scanners at this slice point. Also in position to gain traction in the marketplace is China-based Neusoft Medical Systems, whose NeuViz 16 cleared FDA review earlier this year. The scanner features an advanced detector and dynamic focal spot for high spatial resolution, along with a proprietary DoseRight Modulation feature and a specially designed pediatric protocol to minimize patient dose.
     For those who need more, vendors’ 128-slice CT, and in Toshiba’s case, the 160-slice Aquilion Premium making its RSNA debut this year, provide insurance as much as performance. These scanners are compromises for hospitals that need high performance but whose hamstrung budgets demand a cost-friendly choice. In-between systems offering 128 or 160 slices hit the sweet spot of these economic times, providing an upgrade path to the high end while minimizing capital expenditures.
    Ironically, although the slice wars have ended, the slice monikers remain, convenient handles for discriminating levels of performance. Displacing slices in customers’ minds as purchasing discriminators may be how well scanners can limit patient dose.
    Last year GE launched its ASIR (adaptive statistical iterative reconstruction) software. User evidence reported last summer at the International Symposium of Multidetector-Row CT in San Francisco shows that ASIR cuts patient dose between 22% and 66%, depending on patient body type and application, with no change in spatial or temporal resolution. And ASIR is just the beginning. A more complex iterative technique, called model-based iterative reconstruction (MBIR), may lead to further reductions or better image quality in the future. Because the algorithm is computationally intensive, however, computers must get faster or the algorithm must get simpler before the technique can enter mainstream practice.
    GE can be expected to play the iterative reconstruction card again at this year’s RSNA show, but it will not be the only one doing so. Siemens will come out with its own version, dubbed IRIS (iterative reconstruction in image space). Siemens’ proprietary IRIS uses raw data acquired by the CT system, according to André Hartung, Siemens vice president of CT marketing and sales.
    Early results from IRIS prototypes now in clinical use indicate up to a 50% dose reduction without compromising image quality. These experiences have generated data scheduled for peer-reviewed journal publication, possibly before the RSNA meeting, Hartung said.
    These beta test sites are focusing initially on evaluating the dose reduction capabilities of IRIS on Definition scanners that offer only a single source of x-rays. This group is composed of the Definition AS (Adaptive Scanner) family with 20-, 40-, 64- and 128-slice versions. The Definition brand also covers dual-source configurations. Hartung expects IRIS to be available for all Definition products, including Siemens’ dual-energy Definition Flash CT.
    The iterative reconstruction package may be shipping on new systems as early as spring 2010, he said. An upgrade is being developed for installed Definition systems.
    Hartung expects that IRIS, when applied to the Definition Flash, will allow users to cut dose beyond an already low 1 mSv for scans of the thorax, including the heart. Meanwhile, results have been presented that indicate dual-source imaging can cut dose in selected cases, even without IRIS. These involve eliminating the need for precontrast images when contrast-enhanced studies are indicated.
    Dose savings might be achieved through single-source CTs that switch between two energies, a capability being studied by vendors other than Siemens, just as iterative reconstruction algorithms offer dose-reduction opportunities through postprocessing. Philips execs are not saying exactly what the company has in mind regarding low-dose unveilings at the RSNA meeting. Jason Plante, Philips director of global field marketing, refused to formally release details about Philips’ plans for Chicago, saying only that “we will be unveiling a technique to dramatically reduce dose.”
Whatever the announcement, it will be presented as complementary to an already dose-efficient imaging chain from x-ray tube to detector with technologies for filtering unneeded radiation, Plante said.