Cardiac Mariners launches SBDX digital cardiac catheterization system

Unit produces improved images with less radiation

Digital x-ray developer Cardiac Mariners made its market debut this month with a new digital cardiac catheterization lab that the company believes represents a major leap forward in x-ray technology. The Los Gatos, CA, firm is launching its scanning beam digital x-ray (SBDX) device, which uses what the company calls computed fluoroscopy to obtain cardiac cath images with a small-area digital detector and a large-area x-ray source. SBDX was displayed at the Transcatheter Cardiovascular Therapeutics meeting in Washington, DC, last week.

Cardiac Mariners was established in 1992 and received Food and Drug Administration clearance for an earlier version of the SBDX device two years ago that covered basic fluoroscopic applications (SCAN 10/1/97). The company has waited to market the unit, however, until it gained FDA clearance for an incarnation of SBDX that has cine mode capability, according to Barclay Dorman, vice president of marketing and sales for the company. That clearance came this month.

"We felt we needed to have the better image quality (before going) to market," Dorman said.

Traditional fluoroscopy units emit a diverging x-ray beam from a single x-ray source to a large-area detector. The beam creates a 2-D image that is transformed into an electrical signal before being displayed on a monitor. But Cardiac Mariners' device owes its innovation to reverse geometry: The SBDX digital detector is roughly 2 inches square, while its x-ray tube source is about 10 inches in diameter.

The unit's x-ray source is a cathode-ray tube that functions much like a typical cathode or television tube, except that x-rays are emitted instead of visible light. The source projects a number of thin beams to the detector through a metal collimator riddled with roughly 10,000 transparent channels. The detector is made of cadmium zinc telluride (CZT), a compound that translates the x-rays directly into electrical signals. X-ray beams move left to right through the collimator and converge in the detector, sequentially imaging the entire field-of-view, rather than flooding the area with radiation. Data from the detector are reconstructed in dedicated computer processors at a rate of up to 30 frames per second.

The device's reversed configuration reduces x-ray scatter hitting the detector to insignificant levels, which Cardiac Mariners claims creates better images and decreases radiation levels by a factor of up to 10 times for patients and five times for physicians, as compared with conventional fluoroscopy systems. Therefore, SBDX can provide cine mode image quality at fluoro-radiation dosage levels.

How does the technology compare with other new developments in digital x-ray, such as flat-panel detectors that use either amorphous silicon or amorphous selenium rather than CZT? It doesn't, according to Dorman.

"All of us in the industry have been so used to a certain technology platform that it's hard to make a leap to something different," he said. "This is fundamentally different, from the components we use to the concept of how we acquire the data. Flat panels are component changes on existing technology-swapping the image intensifier for a flat panel. (They don't) change the efficiency of photons, the radiation, or the image quality."

As it begins its marketing effort, Cardiac Mariners plans to emphasize the improved image quality the SBDX units can produce, their reduced radiation scatter, and the lower operating cost that is a result of the x-ray source's lack of moving parts. The firm has no immediate plans to establish marketing or licensing partnerships with OEMs, choosing instead to market the unit itself in the U.S. The company will seek partners in Europe and Asia Pacific, however. SBDX should list for approximately $1 million, roughly the same price as traditional cath labs.

Despite the promise of its technology, Cardiac Mariners is a relatively unknown company and may face challenges trying to sell a new, expensive system in a pinched medical imaging market. With the booming replacement and interventional cardiology markets as its primary targets, however, the firm remains confident of its product's potential.

"Interventional procedures are unique in that they combine technologies: imaging, stent and catheter, and (contrast) agent. There's been a lot of innovation in devices and agents, and we're hearing that people have been waiting for a change in the imaging part," Dorman said.

The company holds 10 U.S. patents, which protect its proprietary x-ray source, the detector, and image reconstruction technologies. The firm hopes its SBDX technology could be used for other fluoroscopic uses such as angiography. Cardiac Mariners plans to begin shipping units next year.