Report from NCRP: Interventionalists need better methods to track radiation exposure

Radiation doses make fluoroscopy-based image guidance the third largest source of ionized radiation exposure in medical imaging. Dr. Stephen Balter has a plan to help interventional radiologists manage the associated risks more capably.

Speaking Monday at the 2007 National Council on Radiation Protection and Measurements meeting, Balter reviewed actions already taken by the Society of Intervention Radiology to address the problem and presented proposals that can do more to protect patients and healthcare practitioners who are directly involved with fluoro-guided procedures.

He noted that fluoroscopy-based diagnostic and interventional procedures can expose patients to higher doses than most imaging modalities that use ionizing radiation. For this reason, SIR made the documentation of patient dose a recommended clinical standard of practice in 2004.

Typical measurement parameters such as fluoroscopic time, however, may not clearly define what kind of short- or long-term effects patients will face, said Balter, an associate professor of radiology at Columbia University Medical Center.

Modern fluoroscopy systems can record the total concentration of radiation expressed in gray units, also known as the kinetic energy released per unit mass of air (kerma). They can read and store the kerma area product delivered to a specific point during a procedure, said Balter, who also serves as the medical physicist in the interventional cardiology laboratory at Columbia.

"These two direct measurements provide a much better indication of patient risk than the older items," he said. "Fluoroscopic time, in particular, should not be the only metric used to manage high-dose interventional procedures."

Balter suggested that data on the amount of radiation dose that patients receive under fluoroscopy be stored and organized under the categories of patient risk supervision and quality assurance. The former could help evaluate patients' risk for deterministic, or short-term, radiation injuries. The latter could assess the risk of stochastic or acquired leukemia or cancer and would keep individual and departmental performance in line with established guidelines or standards.

The process of dose data collection moves from manual recordings of basic imaging systems into the highly sophisticated DICOM standard. The DICOM-DOSE project, a partnership between the International Electrotechnical Commission and the DICOM initiative, could enable collection of complete dose data from all modalities independently from their associated clinical images.

Digital, automated data gathering and storing would in turn allow for a reliable, more cost-effective analysis, Balter said.

"Data should be collected for all procedures where there is any possibility of a deterministic radiation injury," he said. "Appropriately sampled data should be sufficient for quality assurance purposes and for estimating stochastic risk."

Special section: Exclusive coverage of the 2007 National Council on Radiation Protection and Measurements meeting

This year's historic NCRP meeting reveals the disturbing growth of patient exposure to ionizing radiation from medical imaging and proposes practical solutions to regulate its growth. Extended coverage from Diagnostic Imaging lays out the facts and recommendations to better protect patients, physicians, and medical staff.

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