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LAS VEGAS -- A radiation detector that emits audible beeps might help interventional cardiologists and others in the cardiac catheterization laboratory reduce their exposure, researchers found.

When the device, which provides real-time feedback, was used, exposure to the operators was reduced by a relative 29% to 36% compared with cases in which the device was not used, according to Georgios Christopoulos, MD, of the in Dallas and the VA North Texas Health Care System.

There were suggestions that patient exposure was reduced also, although the differences did not reach statistical significance, possibly because of the lack of power, he reported at the Society for Cardiovascular Angiography and Interventions meeting here.

The device -- the Bleeper Sv monitor made by Vertec Scientific -- is "a low-cost and effective tool to visualize radiation and protect ourselves and our patients from its consequences," Christopoulos said.

"Our study results show that ... device use should be encouraged in the cardiac catheterization setting to reduce exposure," he said, "as it has a definitive impact in reducing operator exposure and a potential benefit for reducing patient exposure, as well."

Radiation exposure has been tied to increased risks of cataracts and brain tumors in interventional cardiologists and of tissue injury and cancer in patients.

Currently, silent dosimetry devices are used to monitor radiation exposure in the cath lab, but they have the disadvantage of providing results months later. Some devices have now been developed to provide real-time results, which allows clinicians to modify what they're doing to reduce exposure as it's occurring.

In the RadiCure study, Christopoulos and colleagues evaluated the use of the Bleeper Sv monitor, which beeps about once every 15 minutes in the presence of background radiation, with the frequency increasing along with the dose of radiation. In response to greater beeping, clinicians can take measures to reduce exposure, including readjusting the position of the shield, changing their position in relation to the radiation source, decreasing the fluoroscopy dose, or using surgical drapes that absorb radiation.

The trial randomized 505 patients with clinical indications for coronary angiography with or without percutaneous coronary intervention (PCI) to have monitors used or not used during the case. About 65% of the procedures were diagnostic only, about 10% involved PCI only, and about 25% included both.

The patients were generally well matched, although those who had monitors used were older (66 versus 64), less likely to be male (98% versus 100%), and more likely to have peripheral arterial disease (21% versus 14%).

Radial access was used in 18% of the cases, with no between-group difference. Procedure times also did not differ significantly between the two groups.

For exposure to the first operator, there was a significant reduction in radiation exposure when the Bleeper Sv device was used, from 1.4 to 0.9 millirem (P<0.001). A slightly smaller, but still significant relative reduction in radiation exposure was seen for the second operator, as well (from 0.7 to 0.5 mrem, P<0.001).

There were no differences between the Bleeper Sv and control groups in terms of contrast volume (122 versus 125 mL, P=0.184) or fluoroscopy time (6.0 versus 6.6 minutes, P=0.223).

, of the University of Texas Health Science Center at Houston, who co-chaired the session at which the results were presented, asked Christopoulos how there could be a reduction in radiation exposure without a reduction in fluoroscopy time, which has been shown to be a main determinant of exposure in prior studies.

Christopoulos responded that changes performed by the operators upon hearing the beeping -- changing the position of the shield, for example -- might explain the discrepancy.

The other co-chair of the session, , of the University of California San Francisco, highlighted the importance of radiation safety to the field of interventional cardiology.

"The bottom line is, I think as we move forward in ... doing more anatomic procedures, this could prove to be an important adjunct in physician behavior to decrease exposure," said Brindis, who is a past president of the American College of Cardiology.

Christopoulos acknowledged some limitations of the study, including the use of patients from a single center, the lack of statistical power to detect difference in exposure to patients, the nonblinded design, and the lack of a formal protocol for reducing exposure in response to the beeps.

From the American Heart Association:

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