Interventionalists bone up on radiation dose risks

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CHICAGO—As snow swirled outside Lakeside Center Monday morning, attendees to the 94th annual meeting of the Radiological Society of North America (RSNA) packed themselves into a room to hear about radiation risks for interventional radiologists during the multisession course “Radiation Dose: Are We at Crisis?—Protecting Our Personnel.”

Presented by John F. Angle, MD, associate professor of radiology at the University of Virginia Health System in Charlottesville, and sponsored by the Associate Sciences Consortium, the course was designed to education attendees on how to identify three ways to markedly reduce the moment to moment patient dose in a procedure; understand the difference between air kerma, absorbed dose and organ dose as it relates to IR procedures; and outline a plan to monitor patient and operator dose for a practice.
Despite evidence that operator radiation exposure has decreased over time, radiation exposure in the interventional radiology (IR) suite is often taken for granted, said Angle, adding that precedence over the delayed potential complications of radiation exposure.  However, all the staff and operators in the room must work to minimize patient and operator exposure. “In a population of 10,000 people, four excess deaths are expected from 10mSv of exposure,” Angle said. He noted, however, that 88 percent of radiologists get exposed to less than 0.5mSv per year, mainly from scatter from the patient during a procedure.
He told attendees that there are three basic concepts radiation physicists apply to reducing these doses: time distance and shielding. “There are easily applicable habits that can be accepted in the IR suite that will greatly reduce patient dose,” he said.

Interventional radiologists must provide practical and accurate consultation to patients prior to procedures, particularly for procedures on young patients or pregnant women.  An understanding of radiation exposure, dose and organ dose is necessary to complete these concepts.  He added that operators most at risk for radiation exposure are fluoroscopy and digital acquisition interventionalists, and IRs who perform CT-guided procedures.

IRs must be prepared to record patient dosimetry in the future, he said. Although there are many levels of detail and methods of measurement, a system must be in place.  Fluoroscopy time, dose-area product and skin entry dose are concepts that need to be familiar prior to the practicing IR. He said that operators must work to protect the patient and themselves, to ensure that they receive the lowest radiation dose possible.

Also as part of this course, Bruce H. Alexander, PhD, associate professor, division of environmental health science at the University of Minnesota in Minneapolis, presented results from the U.S. Radiologic Technologists Study (USRT) ongoing study of a population of 146,022 technologists registered with the American Registry of Radiologic Technologists.

The USRT study, a collaborative effort of the University of Minnesota and the National Cancer Institute, is one of the largest studies of occupational exposure ionizing radiation in the medical field. It was originally designed to study cancer incidence in relation work-related exposure, but has expanded to include other health conditions and the molecular biological response to ionizing radiation exposure including genetic and genomic factors, according to Alexander.

To date, the study has revealed some evidence of associations between employment as a radiologic technologist before 1950 and the risk of breast cancer, thyroid cancer, skin cancer and hematopoietic malignancies. He said that other analyses have demonstrated potential genetic markers of susceptibility to radiation exposure and markers of cancer risk and new exposure reconstruction models will evaluate these initial results. “As with all observational epidemiology studies the key to interpreting the results lies in understanding the methods and relevant assumptions in the analyses,” according to Alexander.