A Revolution In Medical Imaging

Digirad's 50-pound device could replace 3,000-pound gamma-ray cameras

Cell phones on chips. Cameras on chips. It's amazing how many complex systems have been shrunk onto tiny slices of silicon. But in three decades of high-tech diminution, there has been one stubborn holdout: The nuclear-detection devices doctors use to diagnose cancer and arms experts require to monitor nuclear weapons.

Now, a scrappy, three-year-old startup called Digirad Corp. intends to shake up the field of gamma- and X-ray detectors. The San Diego company is producing crystal sensors mounted on semiconductors that can replace the bulky vacuum tubes in nuclear medical gear. And unlike crystal sensors used by the military, which function only when supercooled in liquid nitrogen, Digirad's crystals work at room temperature. That opens the door to dozens of applications, from smog sensors to airport detectors for thwarting transport of drugs and explosives. "We've been waiting with bated breath for this kind of thing," says Anthony D. Lavietes, an electrical engineer at Lawrence Livermore National Laboratory in Livermore, Calif.

In June, with the blessing of the Food & Drug Administration, Digirad unveiled its first product: a 50-pound imaging device that could replace 3,000-pound gamma cameras used in nuclear medicine. The product is winning raves from doctors who have field-tested it. "The images are superb," says Michael Kipper, associate professor of radiology at the University of California at San Diego.

DEEP HORIZON. Nuclear medicine could use a boost. Hospitals will spend about $540 million on gamma cameras this year, says Frost & Sullivan in Mountain View, Calif. They'll measure bone density in osteoporosis sufferers and tissue damage in heart patients as well as detect cancers. But the market--supplied mainly by the likes of Siemens, General Electric, and Toshiba--has been languishing for years because of high equipment costs and limited uses.

Having tried Digirad's alternative camera over a six-month period, Kipper thinks it could expand the boundaries of nuclear medicine. Unlike conventional gamma cameras, Digirad's products could be installed in small breast-cancer clinics, where their ability to image the breast from different angles could reduce dependence on biopsies. These compact cameras could also be placed in hospital emergency rooms to speed diagnosis of heart attacks.

The principles of gamma-ray detection haven't changed since the devices were invented in the 1960s. They all rely on crystals that generate either flashes of light or electrical signals when they absorb X-rays or gamma rays (illustration). The rays are given off naturally in the case of radioactive substances, and can be induced in most other materials--including the human body--by exciting the atoms with a radiation source. Each irradiated substance--whether it's a tumor or a hunk of steel--emits energy differently. So if you can accurately measure the rays, translated into electrical signals, you can identify most materials.

For decades, scientists trying to evaluate the condition of nuclear warheads and other weapons relied on pure germanium crystals chilled in liquid nitrogen. But in the mid-1980s, Digirad founder Jack Butler and a Ukranian collaborator named Emmanuil Raiskin showed that a combination of cadmium, zinc, and telluride (CZT) offered excellent electrical properties at room temperature. The two men founded San Diego Semiconductor, which later became Digirad. By the early 1990s, convinced of CZT's merits, both Livermore and Sandia National Laboratories began helping Digirad analyze and test its crystals.

The payoff could be huge, says Ralph B. James, a solid-state physicist at Sandia. In addition to medical and weapons-related applications, James thinks CZT will help scientists track toxic elements in the environment, measure lead in paint, analyze oil deposits, and separate aluminum into its alloys for recycling purposes. Contemplating all these opportunities, Digirad President and CEO Karen A. Klause exuberantly predicts that annual demand for CZT detectors could soar to $10 billion over the next decade.

Digirad won't be the only company trying to harvest that business, however. Bicron, a Newbury (Ohio) unit of France's industrial giant St. Gobain, is developing similar materials--assisted by Emmanuil Raiskin, who parted ways with Jack Butler in 1991. Bicron is the world's leading supplier of sodium-iodide crystals used in nuclear medicine. "But we don't have our boat tied to any one product," says Philip J. Corvo, Bicron's general manager for scintillation products. Manufacturers of current gamma cameras, such as GE, may also enter the fray. "The whole picture could change as new players get interested in the technology," says Sandia's James.


CHEAPER, TOO. Analysts say Digirad has at least a 12-month lead over rivals in the medical arena, the biggest niche, for now. It recently doubled its staff, to 53, and is closing a $15 million round of venture-capital financing. That, plus a $6 million placement last September, should cushion Digirad until volume sales begin in the second half of 1998. Prices start at about $250,000, and high-end units with a large viewing field will cost $100,000 more. But that's still just half the price of premium gamma cameras.

CEO Klause hopes to list Digirad in mid-1998, at which time she'll take the wraps off the company's next line of products--crystal-based CT and X-ray gear that will require less radiation than today's equipment. Meanwhile, excitement over the new gamma cameras is mounting. If they perform as advertised, says Arturo E. Beeche, Frost & Sullivan's analyst covering radio pharmaceuticals, "these devices will be nothing short of revolutionary."

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