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From: J on 19 Jul 2008 08:55
http://www.fda.gov/cdrh/safety/071408-ctscanning.html
FDA Preliminary1 Public Health Notification:
Possible Malfunction of Electronic Medical Devices Caused by Computed
Tomography (CT) Scanning

Date July 14, 2008

Dear Healthcare Professional:

This is to alert you to the possibility that the x-rays used during CT
examinations may cause some implanted and external electronic medical
devices to malfunction, and to provide recommendations to reduce the
potential risk.


Most patients with electronic medical devices undergo CT scans without any
adverse consequences. However, FDA has received a small number of reports
of adverse events in which CT scans may have interfered with electronic
medical devices, including pacemakers, defibrillators, neurostimulators,
and implanted or externally worn drug infusion pumps. There have been
similar reports in the literature.2-4

It is possible that this interference is being reported more frequently
now because of the increased utilization of CT, the higher dose-rate
capability of newer CT machines, an increase in the number of patients
with implanted and externally worn electronic medical devices, and better
reporting systems.

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

In the reports received by FDA, the following adverse events were likely
to have been caused by x-rays from CT scans:

* Unintended �shocks� (i.e., stimuli) from neurostimulators
* Malfunctions of insulin infusion pumps
* Transient changes in pacemaker output pulse rate

Note that malfunctions of this kind, which can result from direct exposure
of the medical device to the high x-ray dose rates generated by some CT
equipment, are different from those related to MRI scanning, which are
caused by strong electric and magnetic fields.
Recommendations

Before beginning a CT scan, the operator should use CT scout views to
determine if implanted or externally worn electronic medical devices are
present and if so, their location relative to the programmed scan range.

For CT procedures in which the medical device is in or immediately
adjacent to the programmed scan range, the operator should:

* Determine the device type;
* If practical, try to move external devices out of the scan range;
* Ask patients with neurostimulators to shut off the device
temporarily while the scan is performed;
* Minimize x-ray exposure to the implanted or externally worn
electronic medical device by:
o Using the lowest possible x-ray tube current consistent with
obtaining the required image quality; and
o Making sure that the x-ray beam does not dwell over the device
for more than a few seconds;

Important note: 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.

After CT scanning directly over the implanted or externally worn
electronic medical device:

* Have the patient turn the device back on if it had been turned off
prior to scanning.
* Have the patient check the device for proper functioning, even if
the device was turned off.
* Advise patients to contact their healthcare provider as soon as
possible if they suspect their device is not functioning properly after a
CT scan.

Background

Experimental studies with anthropomorphic phantoms have demonstrated the
potential for high dose rate CT irradiation to affect implanted cardiac
rhythm management devices.3,4 Some occurrences in patients, which involved
neurostimulator and pacemaker devices, have also been reported to FDA and
appear in the literature.3,5

Electronic medical devices that theoretically could be affected by CT
x-rays include, but are not limited to:

* cardiac pacemakers,
* implantable cardiac defibrillators,
* neurostimulators,
* drug infusion pumps, including insulin pumps,
* cochlear implants, and
* retinal implants.

While theoretically possible, reports of CT interference with cochlear
implants and retinal implants have not been received to date.

Problems with electronic medical devices that might be caused by CT
scanner interference include:

* generation of spurious signals, including cardiac defibrillation
pulses
* misinterpretation of signals produced by the x-rays as actual
biological signals
* missed detection of actual biological signals
* resetting or reprogramming of device settings

The type of effect, if any, is likely to depend on the device type, the
manufacturer and the model.
Reporting to FDA

FDA requires hospitals and other user facilities to report deaths and
serious injuries associated with the use of medical devices. If you
suspect that a reportable adverse event was related to the use of CT
equipment, you should follow the reporting procedure established by your
facility.

We also encourage you to report adverse events that do not meet the
requirements for mandatory reporting. You can report directly to MedWatch,
the FDA Safety Information and Adverse Event Reporting program. You may
submit reports online at www.fda.gov/MedWatch/report.htm, by phone
1-800-FDA-1088, or by returning the postage-paid FDA form 3500 which may
be downloaded from www.fda.gov/MedWatch/getforms.htm by mail to MedWatch,
5600 Fishers Lane, Rockville, MD 20852-9787 or fax 1-800-FDA-0178.
Getting More Information

If you have questions about this Notification, please contact Issues
Management Staff, Office of Surveillance and Biometrics (HFZ-510), 1350
Piccard Drive, Rockville, Maryland, 20850, by Fax at 240-276-3356, or by
e-mail at phann(a)cdrh.fda.gov. You may also leave a voicemail message at
240-276-3357 and we will return your call as soon as possible.

FDA medical device Public Health Notifications are available on the
Internet at http://www.fda.gov/cdrh/safety.html. You can also be notified
through email on the day the safety notification is released by
subscribing to our list server. To subscribe, visit:
http://service.govdelivery.com/service/subscribe.html?code=USFDA_39.

Sincerely yours,



Daniel G. Schultz, MD
Director
Center for Devices and Radiological Health
Food and Drug Administration


1 CDRH Preliminary Public Health Notifications are intended to quickly
share device-related safety information with healthcare providers when the
available information and our understanding of an issue are still
evolving. We will revise this Notification as new information merits and
so encourage you to check this site for updates.

2 �Does High-Power Computed Tomography Scanning Equipment Affect the
Operation of Pacemakers?,� Yamaji, S., et al., Circulation Journal
70:190-197 (2006).

3 �Effects of CT Irradiation on Implantable Cardiac Rhythm Management
Devices,� McCollough, C., et al., Radiology 243 (3):766-774 (2007).

4 �Hazard Report�CT Scans Can Affect the Operation of Implanted Electronic
Devices,� ECRI Institute Problem Reporting System, Health Devices 36
(4):136-138 (2007).

5 MedSun is the FDA's Medical Product Safety Network of 350 hospitals
spread throughout the United States. Information from 132 of these
facilities indicated that they have not experienced any CT medical device
interference, while 3 have had from 1 to 3 events that may have been CT
scan induced. Fifteen MedSun facilities indicated they take some
precautionary steps when CT scanning patients who have electronic medical
devices.

Updated July 14, 2008

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