Cell Point, Philips bet on next generation of radiotracers

Vendors are pursuing high-powered SPECT/CT not because the current field of radiotracers demands it or because SPECT/CT is the next logical step after PET/CT. They're not assembling million-dollar-plus hybrids because 64-slice CT angiography has pushed into the coronary frontier. The real reason behind the development of premium-performance SPECT/CT can be found only in the future, in 12 to 18 months.

By mid-2008, Cell Point, a company with a skeleton staff of executives at the helm, expects to turn the nuclear medicine community on its head with a radiotracer that, if successful, will do for SPECT what FDG did for PET.

Like FDG, this radiotracer, called ECDG (ethylenedicysteine-deoxyglucose), is like candy to cancer. Miscreant cells gobble this glucose-based agent just as they do with FDG - maybe more so. Unlike FDG, which depends on short-lived fluorine for its glow, however, ECDG bonds to one of the most commonly used radiotracers in nuclear medicine, technetium.

"Like most of nuclear medicine, ECDG (agents) will come from kits that are kept on a shelf, waiting for patients," said Cell Point president Dr. F. David Rollo.

Rollo bought into ECDG as the gateway to molecular imaging six years ago. But it wasn't just the ease of handling and administration that did it. The icing on this radioactive cake was found at the business end of ECDG, which bonds to the high-velocity radioisotope rhenium as well as it does to technetium. Swapping in rhenium for technetium transforms the diagnostic agent into a therapeutic one.

"The real power of molecular imaging is target-specific imaging for target-specific diagnosis and therapy," Rollo said. "PET only has the first half, and it's limited by availability."

At the time Rollo imagined this renaissance of gamma-based imaging, he was chief medical officer of Philips Medical Systems. His belief in the potential of ECDG launched SPECT/CT into the stratosphere of CT imaging. As Philips CMO in 2003, Rollo struck an alliance with Dutch higher ups and convinced them to take an equity stake in Cell Point, setting in motion developments that have laid the groundwork for SPECT/CT with ECDG.

The CT component, he argued successfully, would be essential to the correct diagnosis of ECDG scans. The technetium data recorded by a gamma camera, he explained, would show only the hot spots in the body where ECDG was selectively consumed.

"That meant we needed to do fusion with CT," he said.

Knowing the exact position of these spots would be important not only when differentiating lung and abdominal cancers, but also when diagnosing heart disease. ECDG, it turns out, is selectively taken up by ischemic tissue. This additional facet of the radiotracer platform promises to make ECDG all the more appealing to the medical community, as it opens another avenue for applications.

Sixty-four-slice CT will support the assessment of heart patients, outlining the myocardial wall and coronary vessels, just as it will provide the anatomic context for interpreting oncologic images. This argument led Philips leaders to buy into the development and launch of high-end Precedence SPECT/CT hybrids featuring superpremium CTs.

But Rollo knew from the outset that, while important, even the most powerful CT would not be enough. Special software would be needed to interpret the ECDG data.

"Traditional nuclear medicine looks for cold spots, holes in the liver and holes in the heart, whereas molecular imaging with targeted imaging looks for hot spots," he said. "We needed unique reconstruction algorithms for these hot spots, algorithms that would be different for each clinical application."

What Philips and Cell Point did in response led to what could be the least appreciated technology ever launched in radiology: Software positioned by the Dutch company as a workflow enhancer that will realize its true potential only when the next generation of radiotracers enters the market.

Tomorrow: the potential of Philips' Astonish software package and why Siemens, GE, and other makers of gamma cameras will benefit.