The US Food and Drug Administration (FDA) has become aware of radiation overexposures during perfusion computed tomography (CT) imaging to aid in the diagnosis and treatment of stroke. Over an 18-month period, 206 patients at a particular facility received radiation doses that were approximately eight times the expected level.

Instead of receiving the expected dose of 0.5 Gy (maximum) to the head, these patients received 3 to 4 Gy. In some cases, this excessive dose resulted in hair loss and erythema.

The facility has notified all patients who received the overexposure and provided resources for additional information.

While this event involved a single kind of diagnostic test at 1 facility, the magnitude of these overdoses and their impact on the affected patients were significant. This situation may reflect more widespread problems with CT quality assurance programs and may not be isolated to this particular facility or this imaging procedure (CT brain perfusion).

If patient doses are higher than the expected level, but not high enough to produce obvious signs of radiation injury, the problem may go undetected and unreported, putting patients at increased risk for long-term radiation effects.

The FDA encourages every facility performing CT imaging to review its CT protocols and be aware of the dose indices normally displayed on the control panel. These indices include the volume computed tomography dose index and the dose-length product.

For each protocol selected, and before scanning the patient, carefully monitor the dose indices displayed on the control panel. To prevent accidental overexposure, make sure that the values displayed reasonably correspond to the doses normally associated with the protocol. Confirm this again after the patient has been scanned.

The FDA is working with the parties involved to gather more data about this situation and to understand its potential public health impact. As the FDA obtains more information that better defines the problem, we will be better able to determine if there are more widespread risks.