Doctors may order CT scans safely for patients with insulin pumps, cardiac implantable electronic devices, or neurostimulators, according to a preliminary public health notification from the FDA.
“The probability of an adverse event being caused by exposing these devices to CT irradiation is extremely low, and it is greatly outweighed by the clinical benefit of a medically indicated CT examination,” said the agency. The preliminary notification noted a “possibility that the x-rays used during CT examinations may cause some implanted and external electronic medical devices to malfunction.”
In addition, the notification included recommendations to reduce the potential risk of such events. The operator should determine the device type, move external devices out of the scan range, and ask patients with neurostimulators to shut off the device temporarily while the scan is performed, according to the agency. Furthermore, operators should minimize x-ray exposure to the implanted or externally worn electronic medical device by using the lowest possible x-ray tube current consistent with obtaining the required image quality and by making sure that the x-ray beam does not dwell over the device for more than a few seconds. The notification also cited adverse events that a few patients had experienced with medical devices, such as unintended shocks from neurostimulators, malfunctions of insulin infusion pumps, and transient changes in pacemaker output pulse rate.
There is an extremely low probability that a CT scanner directly irradiating the circuitry of certain implantable or wearable electronic medical devices can affect the function and operation of the medical devices, according to the FDA. This probability is even lower when the radiation dose and the radiation dose rate are reduced. The agency also stated that the interference is completely avoided when the medical device is outside of the primary x-ray beam of the CT scanner.
The preliminary public health notification provided additional reports of adverse events by patients with electronic medical devices who had CT scans. The number of such events was small, said the agency, compared with the number of patients with insulin pumps, cardiac implantable electronic devices, and neurostimulators who were scanned without adverse effects. The FDA encourages health care providers and patients who suspect a problem with a medical imaging device to file a voluntary report through MedWatch, the FDA Safety Information and Adverse Event Reporting Program.
—Katie Wagner Lennon