Swiss Study Finds RFID Tags Safe for MRI, CT Scans

In the case of MRI scans, the researchers also tested the system on a live volunteer, and found that the RFID tags did have some effect on MRI images of the volunteer, who wore the tags taped to the wrist. For the MRI images, Steffen says, the tags left a minimal amount of artifacts (misrepresentations) by creating a shadowing effect on the MRI image, but it was minor enough not to affect the quality of these kinds of diagnostic tests. It could, for example, interfere with visibility of the skin directly underneath the tag, but the remainder of the wrist to which that tag was attached was still clearly visible. Therefore, the researchers recommended against placing an RFID tag directly on the region of interest in MRI examinations (a skin lesion or malignant melanoma, for instance).

Another phase of the testing studied temperature increases in tissue next to an RFID tag. This portion of the study was undertaken at the University of ETH Zurich, led by Roger Luechinger, a researcher at the university's Institute for Biomedical Engineering. In this case, tags were attached to a container of saline solution and a gelling agent to mimic the human arm, with sensors installed to track any temperature changes in the solution. The tagged container was then subjected to MR radiation. The greatest increase was determined to be approximately 4 degrees Celsius (7 degrees Fahrenheit). This, the study's authors determined, would be minimally perceptible to those wearing an RFID wristband. When a volunteer then wore the tags taped to his or her wrist, and placed his or her own arm in the MR scanner, the same results were found, he says.

The presence of the wrist tags resulted in only minor distortions of the MR image.

"We conclude that patients wearing RFID wristbands are safe in 1.5-T and 3-T scanners using normal operation mode for RF field when the types of tags tested here are used," the researchers wrote, referring specifically to the two InfoMedis tag models they had evaluated.

The study concludes that "wristbands for patient identification equipped with RFID transponders not containing ferromagnetic components do not have to be removed for MRI and CT scanning." However, the researchers do add the following caution: "Although the types of RFID tags tested in our study are those most likely to be used in hospitals, we are aware of the fact that there is a huge market of different types of RFID tags. These other types of RFID tags need to be tested in different MR conditions and also under other clinical conditions."

As a result of the testing, Steffen indicates, he is confident that RFID-based wristbands are a safe and reliable option for patients, even if they undergo MRI or CT scans. Now that the study has determined that the technology can operate safely in a hospital's imagining environment, he says, the next step is for vendors or users to develop applications for RFID in Swiss hospitals. "It's good to know that a wristband can be left on in an MRI machine," he states, but few hospitals in Switzerland currently require wristbands to identify patients in hospitals (though they are commonly used in the United States, as well as in certain other countries). If Swiss regulations require ID wristbands in the future, he adds, hospitals may begin examining RFID technology as an alternative to bar-coding on wristbands to access patient data.

A copy of the study, entitled "Safety and Reliability of Radio Frequency Identification Devices in Magnetic Resonance Imaging and Computed Tomography," is available online.