To promote the safety of patients undergoing radiation-based cardiovascular imaging—without compromising diagnostic quality—the major stakeholders in the field have produced a report that outlines current shortcomings and offers strategies for future improvement.

The statement, published online March 22, 2012, ahead of print in the Journal of the American College of Cardiology, represents the consensus of a conference jointly sponsored by the Duke University Clinical Research Institute, American College of Cardiology Foundation, and American Heart Association held in February 2011. The 1-day think tank brought together representatives from cardiovascular imaging societies, private payers, government and nongovernment agencies, industry, medical physicists, and patient advocates.

“This effort represents a major step forward to better define the issues and needs around patient radiation safety in cardiovascular imaging, and to develop an action plan to guide future efforts,” said writing/steering committee chair Pamela S. Douglas, MD, of Duke Clinical Research Institute (Durham, NC), in a prepared statement.

The authors emphasize that balancing the risk and benefit of radiation is a complex and difficult task. For example, “for justified procedures, exposure should be optimized to give the lowest possible dose while maintaining image quality to give the highest possible accuracy,” they note. This calculus varies with the clinical scenario; in older patients and those with life-threatening cardiovascular disease, for example, the benefits of accurate diagnosis and optimal management facilitated by imaging may outweigh the minimal or theoretical risks of the required radiation exposure.

Because radiation-based tests should be performed in the right patient, for the right reason, at the right time—and alternatives to radiation should be considered when appropriate—the issue of radiation protection is pertinent to every clinician who makes decisions regarding use of such procedures, the authors observe.

Exposure vs. Biological Dose

Key to any approach to radiation safety, they write, is distinguishing between exposure and dose. Broadly speaking, exposure is the amount of radiation produced by the imaging device. By contrast, the amount of energy absorbed per unit tissue (known as the absorbed dose) varies by organ and body tissue. Although the latter measure is far more relevant to radiation risk, the authors note, it is dramatically affected by multiple patient and technical factors and can only be estimated for a given exam.

In addition, radiation dosimetry metrics differ by imaging modality, making comparison of exposures from different tests difficult. Although the concept of effective dose, a generic estimate of risk with a wide margin of error, is used to compare different scan protocols or imaging modalities, it does not represent the biological risk to an individual patient.

Despite efforts at standardization, “measurement of radiation exposure and risk is controversial, and there is no universal agreement on the appropriate approach,” the authors write.

Targeting Key Areas

The report identifies 4 critical areas requiring attention and sets goals for improvement, calling for collaboration across the range of stakeholders:

• Quantifying the estimated stochastic risks of low-dose radiation associated with contemporary cardiovascular imaging and therapeutic procedures
• Measuring and reporting radiation dose
• Devising strategies to minimize radiation dose, from single episodes of care to systems change
• Providing education and communication for physicians, patients, the public, and the media

Rare Gathering of Stakeholders

In a telephone interview with TCTMD, Stephen Balter, PhD, of Columbia University Medical Center (New York, NY), who attended the conference, said that this kind of collaboration among stakeholders is “fairly unusual.” Almost all the participants contributed to the writing of the final report, he said.

Michael Poon, MD, of Stony Brook University Medical Center (Stony Brook, NY), agreed, telling TCTMD in a telephone interview that the meeting was a “good first step” in identifying problems and suggesting ways to lower exposure. But he added that the paper also underlines the wealth of unknowns, including the fact that “all the conventional ways of measuring radiation dose have inherent problems.”

A distinguishing feature of the consensus statement, Dr. Balter said, is that it provides “the first clear guidance” for doctors who actually order imaging studies. They need a “very thorough knowledge base” to make the best choices, and perhaps this training should be mandatory, he observed. “Until now, most of the literature has focused on the [imaging] providers, so moving some of the emphasis for education to the physicians who order the exams is relatively new.”

Tracking radiation exposure of individual patients is “essentially meaningless,” in part because the overall risk is so low, Dr. Balter said, agreeing with the report. Dr. Poon added another reason: that different centers report exposure in different ways.

On a hopeful note, however, Dr. Balter predicted that emerging technology and a commitment from industry will eventually ensure that imaging equipment provide automatic, standardized dose reporting.

Another useful strategy is participation in registries, which can provide quality benchmarking, said Dr. Balter. “I would like to know if my hospital is using more or less radiation to provide the same spectrum of services as the national average,” he commented. “And if I’m using more radiation, then the next step is to find out why.”

Regulatory agencies and payers can also play a role by identifying and rewarding good imaging practices, Dr. Poon suggested.

Who Will Guide the Public?

Informing the public about radiation risk is another important responsibility, Dr. Poon said, noting that “there is a lot of misinformation circulating in the media.”

According to Dr. Balter, making available a repository of reliable information is “vital,” though which among the many specialty organizations should be entrusted with providing that is a contentious issue. In the end, the government may be the only source widely regarded as unbiased, he added.

“I think this is going to be a landmark paper in terms of setting radiation policies,” Dr. Balter concluded. “My hope is that it will inspire the funding agencies to actually turn some money loose to reach these objectives.”

Douglas PS, Carr JJ, Cerqueira MD, et al. Developing an action plan for patient radiation safety in adult cardiovascular medicine: Proceedings from the Duke University Clinical Research Institute/American College of Cardiology Foundation/American Heart Association think tank held on February 28, 2011. J Am Coll Cardiol. 2012;Epub ahead of print.

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