Hybrid and PET scanners step nto limelight on RSNA exhibit floor

Research backs vendor claims of value

Clinical support for the use of hybrid PET/CT scanners is increasing. That's good news for the nuclear medicine industry, whose leaders have invested heavily in this technology.

At the RSNA meeting, six hybrid systems were shown by four vendors, three of them high-profile companies widely known for their radiology products. The fourth, CTI of Knoxville, is a relative newcomer to direct sales yet has as much experience in positron imaging as its rivals.

CTI created the new Ecat Reveal-RT, introduced amid the fanfare of an RSNA show news conference Nov. 26. Company officials stated that they expect to sell 30 of the new hybrid scanners in the coming year. CTI's handiwork in PET scanners previously appeared exclusively under the Siemens label.

Philips, Siemens, and GE have a head start. They began beating the PET/CT drum a year ago, showing advanced systems as works-in-progress. This year all three were geared up to sell their products.

Philips showcased its Gemini scanner as an open PET/CT combination that splits into stand-alone PET and CT scanners. Siemens exhibited its Biograph, a combination Somatom Emotion CT, outfitted with a multislice detector, and the Siemens top-of-the-line PET scanner, Ecat Exact HR+, featuring a new lutetium oxyorthosilicate (LSO)-based detector.

GE came to the show with its line of Discovery products: LS, VI, and VH. Discovery LS combines a GE LightSpeed Plus CT with the Advance Nxi PET system. Discovery VI is an upgraded version of SMV's Positrace, outfitted with a HiSpeed CT scanner and new crystal (GE acquired SMV in late 2000). Discovery VH is a dual-head gamma camera combined with CT technology.

"As we're putting these out into clinical evaluation sites, we're seeing diagnoses change," said J. Eric Stahre, general manager and technology leader for molecular imaging and genomics. "Where CT may not pick up a lesion, PET will. If PET picks up a lesion that's very small, CT tells you precisely where it is. In terms of follow-up therapy, surgery, or medical recommendations, the two combined are making a difference."

Vendors are not the only ones making claims. Users of the systems are documenting proof that these devices can have an impact on the management of cancer patients. Researchers from the University Hospital of Zurich in Switzerland found that scanning patients with a hybrid PET/CT machine before planned irradiation changed management in 63% of patients. The 30 patients had a variety of malignant tumors, and changes included tumor volume, radiation dose, and radiation intention (curative/palliative).

In a second Zurich study, 99 lesions in 21 patients were detected. PET/CT fusion improved certainty of lesion localization in 60 lesions and increased diagnostic certainty for 45. Fusion imaging reduced 49 cases that had been undecided with PET alone to 17. The false-positive number decreased from three with PET alone to zero with PET/CT, and 16 false-negative studies with PET alone dropped to two with fusion. In addition, the use of CT attenuation-correction software allowed researchers to reduce acquisition time from 44 to 22 minutes.

Feeding the interest in PET/CT is research demonstrating the power of PET itself. A study at the State University of New York at Buffalo found that FDG-PET initiated a management change in 40% of patients with known or suspected colorectal cancer recurrence. Specifically, PET depicted new metastatic sites not previously suspected in 24 of 49 patients scanned for metastatic workup. In 43 patients scanned to determine the extent of disease recurrence, PET findings indicated malignancy in 18, depicting new sites in 13. In 41 patients with equivocal findings, FDG-PET identified the source of carcinoembryonic antigen elevation in 29.

The volume of PET scans and the number of U.S. sites performing them have been increasing rapidly, according to Barbara Franciose, president of the Siemens nuclear medicine division. Like the other manufacturers, Siemens is interested in hybrid systems that enable fusion imaging, but still expects its dedicated PET market to be larger than the hybrid market, she said.

Just because a site has purchased a hybrid scanner doesn't mean the scanner will be used for fusion imaging all the time. From the start, vendors have talked up the idea of using combination PET/CT systems separately to boost revenues. CT scans might alternate with PET scans, for example, as demand builds for fusion scanning.

Philips' Gemini, which combines a premium-performance Allegro PET system and Mx8000 multislice scanner, addresses the idea of separate use. Its entrance on the RSNA exhibit floor this year is a tale of coincidence and opportunity, as neither piece of this product originally belonged to Philips. ADAC Labs developed the PET scanner, while Elscint and Marconi Medical Systems developed the Mx8000. ADAC executives initiated the alliance with Marconi that led to development of the hybrid scanner as part of the Gemini project. By the time Gemini cleared the FDA in October, both ADAC and Marconi Medical were owned by Philips.

Consolidation within the corporate ranks is mirrored in the modalities, as physicians seek definitive conclusions by fusing modalities and the industry tries to accommodate them.

"We'll see the coming together of CT and PET," said Josh Gurewitz, marketing director for nuclear medicine and PET at ADAC. "The line between the modalities seems to be blurring rapidly." n