The CT industry is firmly focused on the future. Companies are looking sometimes years ahead when setting a time frame for clinical applications and technological capabilities. That the future looks bright for CT was underscored at the RSNA show by presentation of early clinical results in coronary angiography, pulmonary screening, and CT colonoscopy. Most, if not all, of these advanced clinical studies were accomplished with quad-slice scanners. Yet, ironically, vendors emphasized work-in-progress configurations supporting eight, 16, or even 32 slices.
Present technology clearly was not exciting enough for vendors to showcase-and for good reason. Four-slice scanners continue their reign at the superpremium end of CT, even though they have been around for more than two years now. Rather than going forward and building up the numbers in multislice, the CT industry has taken a step backward, or maybe laterally, releasing two- and four-slice devices designed to run on slower CT platforms. These scanners are intended to satisfy the needs of less daring or budget-constrained customers. Many ride atop what would otherwise be single-slice scanner families, providing customers with an upgrade path from a conventional single-slice scanner to multislice without the need to bring in a forklift.
This lack of forward progress has led vendors to wage much of their marketing battle with vaporware. Promises of many-slice scanners are being couched in delivery dates one or several years in the future. Usually, these promises depend on the development of technical solutions that are currently beyond the grasp of engineers. Among them are data acquisition systems and computing engines that can handle the flood of data that will come from advanced detectors. Making sense of the data in a reasonable time frame will be just as important and just as difficult to achieve as actually scanning megaslice images.
Research being done with the current generation of quad-slice scanners, however, is providing the means of reaching this future. And, although vendors are looking several years out, objectives that can be achieved within the next 12 months are being set as interim milestones. The ability to meet these goals could serve as a means for gauging whether long-term promises can be kept.
GE Medical Systems
- GEMS jumped its LightSpeed to the Plus version from the system's initial QX/i configuration. LightSpeed Plus offers increased rotational speed and flexibility. The gantry onboard LightSpeed Plus can rotate twice per second, matching the speed of the fastest CTs on the market. Owners of the LightSpeed Plus will also be able to adjust rotational speed in 0.1-second increments from a half to one second, allowing the operator to customize scans to meet the needs of the patient and to optimize data acquisition.
- An eight-slice version of the LightSpeed has cleared the FDA, but its commercial release is still months away. The scanner is expected to enter full production by the end of 2001. In the meantime, GE engineers will be working to bring the production model up to specifications and developing display interfaces that will allow operators to make the most efficient use of the data. These interfaces will link to Direct3D, a workstation add-on to the CT console that reconstructs data as 2-D slices and 3-D images.
- Installed LightSpeed systems will be upgradable to an eight-slice configuration using the detector currently onboard the quad-slice version to generate eight slices. The major change will be an increase in the number of data channels from four to eight. Owners might not want to upgrade to the LightSpeed Plus configuration, however, since implementing variable rotational speed will require substantial changes in the gantry.
- The QX/i configuration, which had been criticized by competitors for its comparatively slow 800-msec rotational speed, will continue in the CT lineup as a low-cost option. This configuration, which was the first commercial multislice scanner in the industry to enter production, was released more than two years ago.
- GEMS debuted a dual-slice version of the HiSpeed product family. The HiSpeed NX/i provides customers an opportunity to buy a single-slice scanner and upgrade to multislice without changing platforms. The number of slices available on the HiSpeed platform will likely increase to at least four, according to the company.
- Development of clinical tools is a high priority at GE Medical. SmartScore, the company's newest coronary calcium scoring package, will aid in functional analysis of the heart. Lung cancer screening, featuring automatic lesion detection and selective volume reconstructions that include the lesion, is in an early stage of development. Studies involving CT colonoscopy and urography are also under way.
- Electron-beam tomography (EBT) went mobile in 2000. Imatron highlighted its introduction of a coach-mounted unit in Oregon, noting that a second scanner is being prepared for road duty.
- The company continued its efforts to differentiate EBT from mechanical scanners, emphasizing inherent advantages in EBT technology, particularly temporal resolution. Speed matters most when doing coronary angiograms, which are particularly susceptible to the motion of the beating heart. Claims by the makers of mechanical multidetector devices that their systems were at least approaching this capability were criticized by Imatron executives, who pointed out that only EBT scanners have FDA clearance to be marketed for this purpose. The company cleared that regulatory hurdle just prior to the 1999 RSNA show.
- Low-dose lung scanning was also highlighted. This capability benefits from temporal advantages that come with EBT, as the fast scan time (100 msec) doesn't allow artifacts that might otherwise result from respiratory or cardiac motion.
- Colonoscopy using EBT has been cleared by the FDA as a marketable application.
Marconi Medical Systems
- A dual-slice version of the Mx8000 entered the Marconi product line. The scanner will replace the aging MxTwin, which was first introduced under the Elscint label nearly a decade ago. The vintage Twin was acquired when Marconi bought Elscint's CT business. By standardizing on the Mx8000 platform, the company will be able to offer customers a direct upgrade to quad-slice scanning and beyond.
- A 16-slice detector, called Infinity, was the CT highlight of the Marconi booth. The work-in-progress is slated for commercial release no sooner than mid-2002. Each of the 16 simultaneous slices will be less than 1 mm thick. With a rotational speed of 0.5 seconds, an Mx8000 outfitted with Infinity will cover 4 cm per second, achieving a coverage speed 12 times faster than current quad-slice scanners. The company claims the speed and thin slices will make the Mx8000 competitive with cardiac catheterization suites, as the new scanner will support routine functional imaging of the heart, including ejection fraction, wall motion, and valve studies. A critical component in 16-slice scanner is Tach technology, an application-specific integrated circuit (ASIC) chip that converts to digital the analog data coming off the detector and then rapidly transfers the data to the computer. The company claims that Tach chips attached to the detector can handle data streams from a 16-slice or larger detector, potentially including flat-panel area detectors.
- When the 16-slice Infinity detector enters production, FACT (fluoro-assisted CT) stands to benefit immediately. Each year Marconi integrates its most advanced CT system with a digital x-ray fluoro system and stereotactic arm (PinPoint) into its LifeFlight CT trauma suite.
- Among the clinical priorities at Marconi is cardiac imaging. The company focused on coronary calcium scoring capabilities as its entree to the field: advanced cardiac scanning and image processing created multiplanar reformatted images to demonstrate soft plaque in the coronary vessels and a virtual fly-through of the coronaries; volumetric imaging of the heart using retrospective tagging; and lung evaluation differentiating normal tissue from diseased, as in the case of emphysema.
- Oncologic applications got a boost from the Acqsim CT, a CT simulator for radiotherapy planning. Compared with preceding versions, the latest system offers a wider bore (85 versus 70 cm) and larger field-of-view (60 versus 48 cm).
Philips Medical Systems
- TrueView promises to get Philips back into the running as a premier provider of CT scanners. The detector includes 16 arrays. Eventually, each array will be activated, providing 16 data channels, which will enable 16-slice scans. The four-slice capability, however, is still a work-in-progress.
- The quad-slice version of the TrueView detector is scheduled to begin shipping in the second half of 2001 as part of the CT Secura, which features a 0.7-second rotational speed. An eight-slice version is due for commercial release by mid-2002. A 16-slice version is expected to be available before the end of 2003. Although CT Secura was initially released as a single-slice scanner, all CT Secura systems in the field are designed to be compatible with the new detectors.
- BeamRight will achieve x-ray efficiency close to 100% by exactly sculpting the x-ray beam to fit the multiple arrays built into the detector. X-ray dose has been a sore spot for the manufacturers of multislice CT scanners, which deliver substantially higher doses than single-slice scanners. The ability to sculpt the beam could cut x-ray dose considerably.
- Philips has developed a reconstruction algorithm, called 3 pi, to optimize the shape of the x-ray beam and thereby reduce artifacts that might otherwise result from the production of more than four slices. The computational load created by eight or 16 slices sparked the development of a novel computing engine incorporating proprietary application-specific integrated circuits.
- Image on Demand will speed the interpretative process by displaying data as a limited number of relatively thick slices, which can then be reformatted as thinner slices when a region of interest is defined. The number of images generated is limited to those needed for inspection.
Shimadzu Medical Systems
- SCT-7800T, announced as a work-in-progress at the 1999 RSNA meeting, began shipping in late 2000. Distribution in the U.S. should begin in January 2001. The system is being manufactured in two configurations, distinguished primarily by rotational speed: one second and 0.75 seconds. Key capabilities on the subsecond version are CT fluoroscopy and virtual endoscopy.
- SCT-6800TXL features an expanded field-of-view, from 42 to 50 cm, over the previous 6800T series. The compact scanner, featuring a one-second rotational speed, can be sited in less than 190 square feet. SCT-6800TXL comes standard with a 3.5-million heat units (MHU) x-ray tube but is compatible with a 4.5-MHU tube.
- Shimadzu has a quad-slice scanner in development. Commercial release is expected in 2003. The company had originally planned to release a dual-slice scanner in 2002 but abandoned the plan when company strategists concluded that the market for such a scanner could not be sustained.
Siemens Medical Systems
- Siemens is developing a 16-slice detector that uses the same kind of array seen in the quad-slice Somatom Plus 4 Volume Zoom. The advanced adaptive array detector, which is scheduled for commercial release in 2002, will allow slices of varying widths. The smallest will be 0.5 mm.
- Advanced clinical applications the company is focused on are coronary angiography, lung screening, and virtual colonoscopy. Retrospective gating of the heart accomplished on the quad-slice Volume Zoom provides a temporal resolution equivalent to 125 msec. This is fast enough to gather motion-free data for volumetric reconstruction of the heart and coronary vascular tree, according to the company. Of particular interest is soft plaque visualization. Low-dose lung evaluation is being examined in concert with scanning techniques, optimized for lung nodule visualization, which use thick slices that can be reformatted into thinner slices when suspicious lesions are found. Colonoscopy with 2.5-mm slices has been shown capable of uncovering polyps and colon cancer.
- Siemens unveiled a dual-slice version of the mid-tier Emotion at the show. Introduced at the 1999 RSNA meeting as a single-slice scanner, Emotion can now be equipped with a multislice detector that generates two simultaneous slices. Rotational speed is 0.8 seconds. Owners of the mid-tier Balance system (a step below the Emotion), which offers a one-second rotational speed, can upgrade directly to the dual-slice configuration Emotion.
- Smile, Siemens' newest CT scanner, features a modular design. The single-slice product is being sold only over the Internet. Sales efficiencies possible on the Web and production efficiencies possible through the system's modular architecture allow Siemens to sell the unit for $245,000. Any of Smile's 15 modular components can easily be swapped out, allowing owners to service their own machines and save on service fees.
Toshiba Medical Systems
- Aquilion highlights focused on enhancements that expand the scanner's quad-slice clinical capabilities. Retrospective gating allows cardiac images to be constructed using slices acquired only during the diastolic phase, minimizing motion artifact and thereby improving image quality. The refresh rate of Aquilion's CT fluoroscopy mode has been tripled to deliver 24 frames per second, allowing better lesion targeting and visualization of needles. Toshiba is developing a cerebral blood perfusion package to help identify cerebral blockages. The work-in-progress capability promises rapid detection of stroke.
- Mid-tier Asteion joined the ranks of multislice scanners, spawning its own family. Asteion Multi comprises three configurations, each using a 34-row detector capable of delivering slices ranging in thickness from 0.5 mm to 8 mm. The three systems are distinguished by the power of their generators and x-ray tubes. Asteion MS 60, a work-in-progress, features a 60-kW generator and 6.5-MHU x-ray tube. Asteion Multi 48 includes a 48-kW generator and 4.0-MHU x-ray tube. Asteion Multi 36 has a 36-kW generator and 4.0-MHU x-ray tube.
- Unlike competing mid-tier scanners designed for single-slice operation and outfitted with a dual-slice detector, Asteion features the same quad-slice detector as is built into the company's flagship Aquilion. The major difference between the Aquilion and Asteion product lines is rotational speed; 0.5 seconds for Aquilion and 0.75 seconds for Asteion Multi.
- The exception is a dual-slice version, Asteion Dual, which offers a 0.75 second rotational speed and a detector equipped with 22 arrays. The work-in-progress Asteion Dual is designed to serve as an entry-level multislice scanner capable of being upgraded to quad-slice.
- An advanced x-ray tube, called MegaCool DF, has been developed for Aquilion. The tube provides 30% greater capacity than earlier x-ray tube technology.