The concept of hybrid scanners took root with PET/CT, which combined anatomic exactness and functional sensitivity in a single package, albeit an expensive one. Equipped with a 16-slice CT and a premium performance PET detector ring, this package can
The concept of hybrid scanners took root with PET/CT, which combined anatomic exactness and functional sensitivity in a single package, albeit an expensive one. Equipped with a 16-slice CT and a premium performance PET detector ring, this package can cost more than $2.5 million. By early next year, however, Siemens and Philips plan to be in full production with less costly hybrids, ones that combine CT with SPECT rather than PET.
The two companies unveiled their products June 20 at the Society of Nuclear Medicine meeting in Philadelphia. Philips' Precedence SPECT/CT marries the company's Skylight gamma camera technology, utilizing vertically hung dual detectors, with its Brilliance multislice CT platform. The Precedence, which is scheduled to begin routine commercial shipments in early 2005, will come in two configurations incorporating six- and 16-slice CT components.
Siemens' TruePoint Symbia combines the company's e.cam dual-detector gamma camera with components from its multislice CT technology. Like Philips, the German company is targeting the beginning of 2005 for commercialization. Symbia will be available in three configurations. One will be a fully configured six-slice scanner. Two versions will be built around a dual-slice detector: one a fully configured product and the other supplied with only the simplest functionality.
This simplest version will offer "one button" CT, according to Markus B. Lusser, vice president of worldwide sales and marketing for Siemens nuclear medicine division. A major function of this "T1" version will be to provide attenuation correction.
"But it is a real diagnostic CT, not pure attenuation correction, as is seen with traditional models," he said, alluding to GE's Infinia Hawkeye.
GE's Hawkeye, introduced some four years ago, features a low-performance CT designed for attenuation correction. Resolution is not high enough to allow the CT data to be read separately as part of the diagnostic process. It is sufficient, however, to provide anatomic references that improve the reading of some nuc med scans, notably those done with Prostascint, a prostate imaging agent developed by biopharmaceutical maker Cytogen.
Although GE Healthcare did not exhibit a version of the Hawkeye platform with diagnostic CT capability at the SNM meeting, Dr. Bill Clarke, GE's chief technology and medical officer, said the company was exploring such options.
Price points for the Precedence and Symbia models will depend on their levels of performance. Neither company offered even ballpark figures, but Leo Gurvich, Philips product manager for Precedence, noted the Precedence platform would list for about the cumulative prices of the separate CT and SPECT technologies. This would put the list price of the 16-slice SPECT/CT at around $1.5 million.
"But we don't want to make reference to prices," he said. "The important thing is that the payoff for the system is the ability to do full CT procedures."
Siemens' Symbia cuts a sleeker appearance than Philips' Precedence, but Philips executives contend their scanner is only a "foot or so" bigger than the Siemens system in floor space. The appearance of a larger footprint is nurtured by the greater height of the Philips SPECT/CT, compared with the floor-hugging Precedence. Subsecond rotational speeds and submillimeter slice thicknesses can vary on both companies' platforms to accommodate the needs of different exams.
Philips and Siemens executives believe the market is ripe for a high-performance SPECT/CT system. Hospitals will be a major focus, but smaller facilities, including private offices, will be targeted as well. Philips sees cardiology practices as particularly attractive.
"A lot of cardiology procedures are moving to private offices. Nuclear cardiology is probably 50% of our business," Gurvich said. "If you take the ability to combine nuclear perfusion with CT angiography, which is starting to be more accepted, you have a very powerful system. With this system in their office, cardiologists have an advantage from a business standpoint."
SPECT grew to prominence in the 1980s and '90s in oncology and cardiology under the banner of the "poor man's PET." Executives from both Siemens and Philips profess a dislike for the moniker in relation to their newest derivative of SPECT. They do not plan to market their new products as low-cost alternatives to PET/CT, but they do recognize that customers might perceive these systems that way.
Nuclear medicine has borne a less complimentary nickname, "unclear medicine"-an anagram of part of its name-due to a lack of spatial resolution. The coming breed of SPECT/CT scanners, with their high-resolution multislice CT components, could remedy that, minimizing the "scientific guestimates" the community has come to rely on.
This new technology promises to pinpoint the exact location, size, nature, and extent of disease anywhere in the body, while providing the data needed to exactly correct for the attenuation of gamma radiation coming from radionuclides.
"The ability to register high-quality SPECT images with anatomical and diagnostic CT will make this 'clear' medicine in the future," Lusser said.
The CT portion of the exam will be completed in less than 30 seconds, several minutes less than is commonly required to perform transmission studies using the line source incorporated into conventional attenuation correction.
The clinical value and workflow advantages of these new SPECT/CT systems will be evaluated at beta sites in the coming months. Siemens executives expect Symbia to provide a kind of one-stop shop that speeds diagnosis in much the same way as PET/CT. Acquiring two studies during a single visit could enhance therapy planning and speed exam time for the practitioner and increase comfort and convenience for the patient.
"We expect that the better the attenuation correction and the better the anatomical landmarking, the better the clinical result," Lusser said. "What might happen is that with SPECT/CT, our clinical partners will reexamine the whole diagnostic process, basically the order in which studies are performed. It could all change with this new platform-I would even call it a new modality."
Symbia and Precedence can be used as hybrid scanners or to conduct separate SPECT and CT exams. In this way, the new products might serve as backups to SPECT and CT scanners already installed at an institution, while adding the dimension of fused anatomical and functional imaging that hybrid scanners provide.
The two companies are also positioning their products for use in the coming age of molecular imaging, when the precision of CT is needed to interpret functional studies utilizing new radionuclides that are now in clinical tests.
"The specificity of these agents will allow you to find the smallest molecules in the body, but the problem is that when you get very targeted, you will want to localize those lesions," Gurvich said. "This is where I see the future going."
This latest generation of hybrid scanners could have a more immediate impact in cardiology. Philips 16-slice Precedence, for example, could put CT angiography in the hands of cardiologists, who might begin using the technology as a means for assessing the coronary arteries. Although executives from both Philips and Siemens say their new products are complementary to PET/CT, their expansion into cardiology could slow the crossover to cardiology of PET/CT from its current stronghold in oncology.
SPECT is more familiar to diagnostic cardiologists than PET. Also, SPECT radionuclides for cardiac imaging are easier to handle than the rubidium needed for cardiac PET. SPECT does not, however, offer the same sensitivity as cardiac PET. This fact could determine which modality ultimately wins out. But the battle will not be decided for years to come. In the meantime, prospective buyers who want the security of knowing their SPECT systems will be able to handle any new developments may gravitate toward SPECT/CT, according to Gurvich.
"When making purchases now, you really have to look five years in the future," he said. "We're focusing on security of investment. We want to make sure our customers feel comfortable."