News Story

High-Sensitivity X-ray Camera Operates at 20 fps

New from Rad-icon Imaging Corp, Santa Clara, Calif, is the Shad-o-Box HS, a high-sensitivity, high-speed stand-alone x-ray camera complete with 12-bit digital interface for direct connection to a frame grabber. Designed to replace small image intensifiers and similar real-time detectors for DR applications, the camera operates in real-time radiography applications at up to 20 frames per second (fps), with the Lanex Fast scintillator option offering optimum resolution and sensitivity.

Rad-icon’s Shad-o-Box HS features a 12-bit digital interface for direct connection to a frame grabber.

The camera’s image detector is 512 x 512 and includes a 2D CMOS photodiode array sensor with 96 ?m pixel spacing; the active sensing area is 2 inches for applications ranging from 10 to 160 kV. A Gd2O2S scintillator screen placed in direct contact with the photodiode array converts incident x-ray photons to visible light, which is then detected by the photodiodes. All the while, a carbon-fiber window shields against ambient light and protects the electronics from accidental damage.

Image data is output over a high-speed 12-bit parallel interface for direct input to a digital frame grabber; a 5V/12V desktop supply powers the camera, which dissipates less than 4 watts.

—C. Vasko

Raising the Bar

An equipment testing device anticipates quality standards for cardiac x-ray imaging

By Dana Hinesly

As the number of procedures performed in the cardiac catheterization laboratory continues to rise, the attention that this specialty receives from regulatory bodies tasked with establishing and maintaining imaging equipment quality standards will increase proportionately. This intense scrutiny provides ample reason for hospitals and imaging centers to take meticulous care of the systems used to diagnose and treat patients.

To this end, a collaborative effort between the Society for Cardiac Angiography and Interventions (SCAI), Washington, DC, and the National Electrical Manufacturers Association (NEMA), Rosslyn, Va, has resulted in the development of a standardized testing device: the phantom. Approved as the NEMA Standard in August 2000 and called the XR-21 Standard Fluoro Benchmarking Phantom, the phantom is a physical device used to test cath lab systems through simulation of normal clinical use for fluoroscopically guided invasive and interventional procedures.

Although the application of this testing protocol and the use of the phantom do not currently require FDA clearance, it is clear that the government watchdog is closely monitoring the standardization process.

“An increasing number of patients have been injured with radiation burns as a result of systems that are not operating appropriately,” said Merrill Wondrow, president of Clart? Imaging Solutions Inc, Elk Grove, Calif. Wondrow attributes a portion of the injuries to multiple procedures and interventions being performed on a patient. A single patient could visit multiple cath labs in a city or across the country in a single year. “The FDA and others have actually documented severe radiation burns, and decreasing those is their primary interest,” he said. “As a result, the FDA distributed a mandate about a year ago highly recommending that recognized programs are implemented.”

Standards of Care

Clart? markets the XR-21 Phantom and has worked closely with the industry and the SCAI to develop testing procedures. The company’s Image Quality Improvement Program includes use of the phantom and a test protocol that work together to provide simultaneous measurements of image quality, including imaging-field geometry, spatial resolution, low-contrast iodine-detecting ability, working thickness range, motion blur, and phantom entrance dose. All tests are performed by a trained, certified technologist using the imaging system configured for normal clinical use.

A comprehensive database composed of results from tests that Clart? has conducted at more than 50 cath labs across the country is used to compare results of an individual lab. This database provides a reference point for the data collected using the XR-21 Phantom to test its cath lab systems.

“In order to get a phantom to the point where it’s usable, you need a baseline of data,” Wondrow said. “The SCAI has not developed a database yet, so we have the only database to which testing results can be compared.” After a site has completed testing, Clart? provides the site with a “means and averages” report for each parameter that has been tested. “We now have a considerable database that we can use to compare a tested lab to others across the country and provide them with feedback of how that system is operating against the national database.”

One of the specific problems tackled by the Clart? Image Quality Improvement Program is optimum dosage for patients. “In most cases, the angiographic equipment passes when we set the Phantom to simulate a patient of 120 to 150 pounds. The problem is, people with heart problems don’t usually weigh 150 pounds. Typically, they are more than 200 pounds—and that’s where the systems really degrade. So, we do all of our testing in two phantom configurations—20-cm and 30-cm thicknesses—to tax those systems to that level,” Wondrow explained, noting that the XR-21 Phantom can simulate a patient somewhere between 200 and 250 pounds. “When a system has been calibrated for 120-pound patients, it leaves the cardiologist with a dilemma, because the system is being used on patients who weigh 200 pounds.”

Image quality is another important parameter of the testing program. Because a system providing inadequate radiation will impact image quality severely, other phantom tests have been created to document image-quality performance. Wondrow also hopes the new flat-panel systems will alleviate some of these problems by allowing cardiologists to visualize a better image with a lower dose.

Test Integration

Facilities interested in learning how their cath labs measure up using this phantom have two options. Smaller facilities often opt for a one-time or annual test, where a tech visits the site and uses the XR-21 Phantom to test cath lab equipment in a standardized method. Or health care organizations can purchase the phantom outright at a fraction of the cost of their imaging laboratory. This investment includes the actual phantom, training, support, and the comparison reports.

“We’re seeing more vendors provide this phantom to their clients at no cost with the purchase of equipment,” said Wondrow, who was also a key part of the process that defined and implemented the DICOM standard. “This is a win-win for everyone, including the vendor, because the customer is using the phantom to make sure the imaging system is working correctly from day one.”

Despite the advances made by NEMA, SCAI, the American College of Cardiology, and companies like Clart?, a recent paper¹ by Wondrow—and colleagues Warren K. Laskey, MD, FSCAI, FACC, and David R. Holmes, Jr, MD, FSCAI, FACC—concluded that much work is still to be done to bring cath labs across the country to a standard level.

The paper states, “There is substantial variation (4- to 6-fold) in fluoroscopic exposure rates. This variation was not consistently associated with improved image quality. In the absence of a predictable benefit of higher (or lower) than average exposure rates, cath lab quality improvement programs must minimize such potentially harmful variability in x-ray exposure.”¹

Eliminating variations like these is the ultimate goal. “Our program strives for achieving that and does so without any finger-pointing,” Wondrow said, “because for the first time, there is a standardized phantom and program with everyone on the same page with their imaging equipment.”

Dana Hinesly is a contributing writer for  Medical Imaging. For more information, contact .

Reference

1. Laskey WK, Wondrow M, Holmes DR Jr. Variability in fluoroscopic X-ray exposure in contemporary cardiac catheterization laboratories. J Am Coll Cardiol. 2006;48:1361?1364.