CT Scans May Cause Medical Device Malfunctions

Yael Waknine


July 15, 2008

July 15, 2008 — Direct X-ray exposure from computed tomography (CT) may cause some implanted and external electronic medical devices to malfunction, the US Food and Drug Administration (FDA) warned yesterday in a preliminary public health notification.

"We are continuing to investigate this issue while working with device manufacturers and raising awareness in the healthcare community," according to the FDA. "To date, no patient deaths have been reported from CT scanning of implanted or externally worn electronic medical devices."

Although most patients undergo CT with no adverse effects, a small number of patients have reported interference with devices such as pacemakers, defibrillators, neurostimulators, and implanted or externally worn drug infusion pumps.

Adverse events have included unintended "shocks" from neurostimulators, insulin pump malfunctions, and transient changes in pacemaker output pulse rate. Although CT interference with cochlear and retinal implants is theoretically possible, no cases have yet been reported.

The reported malfunctions differ from those caused by the strong electric and magnetic fields in magnetic resonance imaging (MRI), the FDA said. The increased number of cases may be due to an increased frequency of CT scanning, the higher dose-rate capability of newer machines, an increased prevalence of device use, and better reporting systems.

In the interim, CT operators should use scout views to determine whether implanted or externally worn electronic medical devices are present. Devices in or immediately adjacent to the programmed scan range should be identified and moved if possible; neurostimulators should be turned off while the scan is being performed.

Technicians should minimize device exposure to X-rays by using the lowest possible X-ray tube consistent with required picture quality and ensure that the X-ray beam does not linger over the device for more than a few seconds.

The FDA notification emphasizes, "For CT procedures that require scanning over the medical device continuously for more than a few seconds, as with CT perfusion or interventional exams, attending staff should be ready to take emergency measures to treat adverse reactions if they occur."

Once the CT is completed, devices should be checked for proper functioning, even if they were turned off for the procedure. Patients with concerns regarding their device should be advised to contact their healthcare provider.

Adverse events related to use of CT imaging should be reported to the FDA's MedWatch reporting program by telephone at 1-800-FDA-1088, by fax at 1-800-FDA-0178, online at http://www.fda.gov/medwatch, or by mail to 5600 Fishers Lane, Rockville, MD 20852-9787.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.