Multirow detectors lead to expanded CT applications

January 12, 2000

Multislice CT has entered the next phase of its evolution as vendors concentrate on the practical, rather than fundamental, aspects of the technology. Multirow detectors and subsecond scanning have created enormous clinical opportunity and thorny

Multislice CT has entered the next phase of its evolution as vendors concentrate on the practical, rather than fundamental, aspects of the technology. Multirow detectors and subsecond scanning have created enormous clinical opportunity and thorny technical problems, both of which were addressed on the exhibit floor at the RSNA show.

Wherever speed was a priority, multislice was there. Cardiac and pulmonary applications grabbed the spotlight, as this new breed of machines can all but eliminate motion artifacts. Trauma and interventional applications were close behind.

Acquiring and processing these large amounts of image data, however, taxes human and machine. Human abilities to comprehend the huge quantity of data, in some instances hundreds of slices, were augmented by new visualization tools that promise to integrate 3-D into the diagnostic mainstream.

This rapid acceptance of multislice as heir to the CT throne has changed the dynamics of the industry, relegating spiral scanning to a lower tier of the product hierarchy.

GE Medical Systems

  • LightSpeed QX/i was the runaway market leader in 1999, with more than 200 systems installed worldwide. GE engineers are reportedly working on a detector upgrade that will increase the number of slices from four to at least eight within the next two years.
  • The LightSpeed has a rotation speed of 0.75 second, but algorithmic techniques can improve temporal resolution to the equivalent of 120 milliseconds, according to the Waukesha, WI, firm. The algorithm uses multiple detector rows to build a model of the heart accumulated over several beats.
  • A new software package automatically measures blood vessels for the placement of stents, and can also be used for follow-up imaging. The package has been tested on the abdominal, aortic, carotid, and intracranial vessels.
  • While at the meeting, GE received FDA clearance to market its neuro-based Perfusion CT offering. The perfusion package is designed to help evaluate patients suspected of stroke by measuring cerebral blood volume, cerebral blood flow, and mean transit time.
  • Two new HiSpeed scanners were introduced as premium products, one in a fixed configuration and the other mobile. The fixed site HiSpeed ZX/i uses Solarix 630, a 6.3-MHU metal x-ray tube, along with the HiLight detector. HiSpeed DX/i M offers the same performance level as HiSpeed ZX/i, but in a mobile configuration.
  • GE announced two methods of reducing dose. First, Smart MA automatically adjusts the x-ray beam to obtain the optimal image quality for the anatomical region. The product is available for HiSpeed and will be ported to LightSpeed in 2000. Second, a single-slice option developed for LightSpeed delivers high-resolution slices at intervals appropriate, for example, when generating a high-resolution chest study. Dose reduction is particularly important in pediatric cases.
  • A new low-tier spiral scanner highlighted the extension of spiral scanning capabilities to low-end systems. The product, called ProSpeed AI in Japan and China and GE CT/e elsewhere, could sell for as little as $200,000. Sales will be directed primarily at markets with constrained budgets, such as developing countries and physician group practices in the U.S., pending FDA clearance. CT/e has many of the advanced features found on the GE HiSpeed and LightSpeed systems, including an SGI computer and SmartTools software that assist in acquiring, preparing, and reviewing images.
  • Direct3D is GE’s answer to information overload resulting from the enormous amount of visual data generated in a single scan with LightSpeed. Direct3D, which has received FDA clearance and will begin shipping in mid-2000, is designed as an add-on to the operator’s CT console, reconstructing and displaying data on the fly as conventional 2-D slices, as well as in three dimensions.

Imatron

  • Coronary angiography took center stage, as Imatron received FDA clearance in mid-November to market its electron beam angiography. The company contends that EBA can rival the gold standard of cardiac imaging, x-ray angiography, as a diagnostic tool for low-risk patients, as well as those who need follow-up after angioplasty or coronary artery bypass surgery. The company estimates that EBA might serve as an alternative to x-ray cardiac cath for as many as 20% to 40% of all cardiac patients.
  • Clinical results displayed in the Imatron booth demonstrated the use of 3-D EBA to visualize high-grade stenoses or blockages in coronary arteries and coronary artery bypass grafts. EBA was also shown as a tool for visualizing and evaluating the function of stents in patients undergoing balloon angioplasty.
  • Engineers continue to improve the underlying EBT technology. Among the improvements integrated over the last 12 months was the development of a solid-state, high-frequency switching power supply weighing 700 pounds, one-tenth the weight of its predecessor.
  • One week prior to the RSNA show, Imatron announced the sale of HeartScan centers in Houston and Washington, DC. The centers were purchased by HeartScan Partners, which also owns and operates the San Francisco HeartScan center. The transaction closed on Nov. 19.

Marconi Medical Systems

  • In keeping with an evolving focus on disease and patient management, Marconi (formerly Picker International) integrated its multislice Mx8000 into a shock/trauma suite. As part of LifeFlight, the multislice scanner is complemented by real-time digital fluoroscopy, called FACTS, and a stereotactic arm, PinPoint. The arm can be outfitted with either a surgical probe, which is tracked in real-time, or an ultrasound transducer. This technological mix allows the combination of CT, x-ray fluoroscopy, and ultrasound in a single episode of care.
  • Evolving image technology has been developed to reconstruct images on the fly for both LifeFlight and the stand-alone Mx8000. Images are reconstructed moments after each gantry rotation, so that critical injuries can be identified instantly. Increased detail is achieved through Flexiscan, using multiplanar reconstruction or 4-D angio volume rendering. When used with LifeFlight, FACTS could be employed to guide an intra-arterial catheter for stent placement, for example, and PinPoint could assist in localizing and planning a percutaneous approach to drain blood from the abdominal cavity.
  • Marconi engineers are trying to adapt amorphous silicon flat-panel technology to conebeam CT. The hope is to create a truly volumetric CT scanner as the successor to multislice scanning.

Philips Medical Systems

  • Although it does not yet have a multislice scanner, Philips has put in place the foundation for such a product. This platform, called CT Vision, was launched at the RSNA show as part of a two-product introduction: CT Secura and CT Aura, both of which have begun shipping (SCAN 11/10/99). Both will be upgradable to multislice when the detector is completed. In the meantime, the company expects that its high-performance single-slice scanners will meet the majority of clinical needs in the CT community.
  • The newly released high-end CT Secura offers a 0.7-second rotation. Subsecond scanning is made possible in part by a 7.7-MHU x-ray tube.
  • The mid-tier CT Aura has the same functionality as Secura but its gantry rotates more slowly, once per second, and the x-ray system is less powerful. Aura can be upgraded to Secura, which would then allow an upgrade to multislice.
  • Integrated into both systems is the ClearView detector, found on previous high-end Philips CT scanners, and RapidView reconstruction, which provides on-the-fly image review throughout the examination. DoseRight has been developed to minimize applied dose without compromising image quality. The DoseRight feature will be shipping at the end of the second quarter.

Shimadzu Medical Systems

  • The work-in-progress SCT-7000T will come in two configurations defined primarily by rotation speed: one-second and 0.75-second. Features include Smart Start software for timing contrast injections, a solid-state detector system, CT Fluoro for interventional radiology, and virtual endoscopy. The operator interface includes a large color monitor, optical touch panel, and mouse operation.
  • A work-in-progress is the integration of SCT-7000 with a mobile C-arm for interventional work. The combined system, now available in Japan and pending release in the U.S., feeds information from the C-arm into the CT console, where the surgeon and radiologist can view both CT and fluoro data sets.
  • The SCT-6800T series has been upgraded to the TXL version, characterized by an increased field-of-view from 42 cm to 50 cm, and greater x-ray tube capacity. The series includes an entry-level, slip-ring CT scanner that can be upgraded to one-second rotational spiral imaging with a coverage of 60 seconds. Rotation speed is one second.

Siemens Medical Systems

  • A new dual-slice configuration, called Somatom Plus 4 Access, features half-second rotation and the same resolution as Volume Zoom. Access establishes an economical entry point for customers who want multislice but will not commit to a super-premium scanner.
  • Somatom Plus 4 remains the primary platform supporting multislice, as both the four-slice Volume Zoom and the two-slice Volume Access are derivatives of the system. In this way, Siemens can offer three different scanners at the premium end with single, dual, and quadruple slice. Cost differentials are about 25% among the various configurations with the Volume Zoom priced at about $1.2 million.
  • Customers will be multislice-compatible with either of two new scanners, Emotion or Balance, both of which are upgradable to the Somatom Plus 4 configuration (SCAN 11/10/99). Emotion, which carries a price tag of about $800,000, features an 800-millisecond rotation. Balance, priced near $600,000, offers a one-second rotation. Both scanners are shipping. A modular upgrade to multislice will involve change-out of the detector only.
  • Cardiac applications of multislice scanning are being developed primarily for interventional patients who require follow-up. A retrospective spiral gating of the data acquired over 20 seconds with Volume Zoom can generate movies of the beating heart as well as a fly-through of the coronary arteries. Motion is frozen using Siemens QuickScan, which utilizes data acquired over a 180º rotation accomplished in 250 milliseconds. Calcium scoring, also a major area of interest, can be accomplished on single- and multislice configurations of the Somatom Plus.
  • Along with cardiac applications, early detection of lung cancer was a clinical highlight at the Siemens booth. Multislice technology is especially well suited to this application, according to the company, because the entire lung can be scanned quickly and at low dose.
  • In development is an economical, low-tier spiral scanner that would compete with the GE CT/e. Engineers are focusing on a slim gantry design that maintains the performance and aesthetics of higher tier Siemens systems.

Toshiba America Medical Systems

  • The long-awaited multislice detector debuted in the Toshiba booth, removing any lingering questions about whether the Japanese vendor would attempt to leapfrog its competition by coming out with a “many”-slice configuration. Like premium detectors from GE, Siemens, and Picker, the Toshiba detector delivers four slices. Several detector rows, however, are combined in each of those slices. Four rows in the center of the detector are each 0.5 mm wide. The other 30 rows, 15 on each side of the center stripe, are each 1 mm wide. As more powerful data acquisition systems are developed, however, future versions of the detector might offer more slices.
  • With the new detector, a multislice Aquillion became available. The half-second scanner, featuring a 60-kW generator and 7.5-MHU tube, was first introduced in 1998 as a spiral, single-slice scanner designed to allow upgrades to multislice when Toshiba released its multirow detector. As of this month, 100 Aquillions have been installed worldwide; 30 offer multislice. None have yet been installed in the U.S., although shipments are expected to begin by the end of the first quarter.
  • To handle the volume of data from multislice scans, Toshiba has developed multitasking tools for generating 3-D reconstructions and 2-D slices, depending on user preferences and the anatomy being evaluated.
  • Asteion, which performs full rotation scans in 0.75 seconds, is upgradable to Aquillion. Two standard configurations are available: the Asteion/VR with a 48-kW generator and the Asteion/VI with a 36-kW generator.
  • Interventional CT, a priority for Toshiba since the launch of Aspire CT in 1996, got a boost with the release of a high-performance CT fluoroscopy package designed for multislice Aquillion. When multislice and Aspire CT are combined, the four slices generated with each rotation provide a wider volume of data through which to follow the progress of a surgical probe.