FDA Addressing Concerns of Excess Radiation Exposure During CT Perfusion Imaging

As part of an ongoing investigation into cases of excess radiation during computerized tomography (CT) perfusion imaging of the brain, the U.S. Food and Drug Administration (FDA; Silver Spring, MD, USA) has provided imaging facilities and practitioners with interim recommendations to help prevent additional problems.

The FDA issued an initial safety notification in October 2009 after learning of 206 patients who had been exposed to excess radiation at Cedars-Sinai Medical Center (Los Angeles, CA, USA) over an 18-month period. Since then, the FDA, working with state and local health authorities, has identified at least 50 additional patients who were exposed to excess radiation of up to eight times the expected level during their CT perfusion scans; these cases so far involve more than one manufacturer of CT scanners. Based on its investigation to date, the FDA is providing interim recommendations for imaging facilities, radiologists, and radiologic technologists to help prevent additional cases of excess exposure.

These recommendations include the guidance for facilities to assess whether patients who underwent CT perfusion scans received excess radiation; that facilities should review their radiation dosing protocols for all CT perfusion studies to ensure that the correct dosing is planned for each study; and that facilities should implement quality control procedures to ensure that dosing protocols are followed every time and that the planned amount of radiation is administered.

Additionally, radiologic technologists should check the CT scanner display panel before performing a study to make sure the amount of radiation to be delivered is at the appropriate level for the individual patient. If more than one study is performed on a patient during one imaging session, practitioners should adjust the dose of radiation so it is appropriate for each study. The FDA is also advising manufacturers to review their training for users, reassess information provided to health care facilities, and put into place surveillance systems to identify problems when they arise.

"The FDA is making progress in the investigation of this problem,” said Jeffrey Shuren, M.D., acting director of the FDA's Center for Devices and Radiological Health. "While we do not know yet the full scope of the concern, facilities should take reasonable steps to double-check their approach to CT perfusion studies and take special care with these imaging tests.”

A perfusion CT study involves sequential acquisition of CT sections during intravenous (IV) administration of an iodinated contrast agent. Analysis of the results allows the physician to calculate the regional cerebral blood volume, the blood mean transit time through the cerebral capillaries, and the regional cerebral blood flow. CT perfusion imaging may provide information about the presence and site of vascular occlusion, the presence and extent of ischemia, and tissue viability. Potential advantages of CT perfusion imaging are that it can be performed using standard CT scanners, which are more widely available and less expensive than magnetic resonance imaging (MRI), and it is less invasive than CT angiography.

Related Links:
U.S. Food and Drug Administration
Cedars-Sinai Medical Center