FDA Working to Prevent Radiation Overdoses During CT Scans

November 9, 2010—The U.S. Food and Drug Administration has been investigating reports that patients undergoing computed tomography (CT) brain perfusion scans were accidentally exposed to excess radiation. The FDA found that when properly used, the CT scanners did not malfunction. Instead, it is likely that the improper use of the scanners resulted in these overdoses. However, the FDA has identified a series or promising steps to enhance the safety of these procedures. These steps could reduce the likelihood of radiation overexposure in the event of improper use of the CT scanners.

The FDA has sent a letter to the Medical Imaging and Technology Alliance, the major professional industry organization for manufacturers of CT scanners and other radiological imaging devices, reporting on the results of the investigation and discussing possible CT equipment enhancements that could improve patient safety. The agency will hold follow up discussions with manufacturers on the changes.

Those changes include:
A console notification to alert the operator of a high radiation dose;

• Providing particular information and training on brain-perfusion protocols to all facilities that receiving base CT equipment, whether or not the facilities purchase the related software enabling quantitative analysis of cerebral hemodynamics;
• Clarification of parameters affecting dose, along with clear instructions on how to appropriately set those parameters; and
• Organization of all dose-related information into one section of each user manual, in a dedicated dose manual, or indexed comprehensively in a concordance covering all manuals.

CT brain perfusion scans produce cross-sectional images of the head that evaluate blood flow in the brain. In an update released recently, the FDA discussed findings of a probe into radiation overdoses in patients who received CT brain perfusion scans in hospitals located in California and Alabama.

Begun in 2009, the FDA’s investigation included information from the states and facilities where radiation overdoses occurred from 2008 to Oct. 26, 2010. The agency also inspected CT scanner equipment manufacturers.

The probe indicated that CT scanners, when properly used, did not result in overdoses. However, the investigation uncovered potential enhancements to CT equipment that could reduce the likelihood of radiation overexposure if improper use occurs – a goal of the agency’s Initiative to Reduce Unnecessary Radiation Exposure from Medical Imaging.

“Improving patient safety is part of our public health mission,” said Jeffrey Shuren, M.D., director of FDA’s Center for Devices and Radiological Health. “Patients should not have to worry that a device designed to diagnose an illness exposes them to unnecessary risks.”

Since the investigation began, the FDA is aware of at least 385 patients who received excessive radiation from CT brain perfusion scans, many undergoing the test to confirm the presence of a stroke, performed at five hospitals in California and one in Alabama.
While unnecessary radiation exposure should be avoided, a medically-needed CT scan has benefits that outweigh the radiation risks. Patients should follow their doctor’s recommendations for receiving CT scans.