Guidelines for the Prevention of Excessive Heating and Burns
Associated with Magnetic Resonance Procedures
In general, magnetic resonance (MR) imaging is considered to be a relatively safe diagnostic
modality. However, the use of radio frequency coils, physiologic monitors, electronically‐
activated devices, and external accessories or objects made from conductive materials has
caused excessive heating, resulting in burn injuries to patients undergoing MR procedures.
Heating of implants and similar devices may also occur in association with MR procedures, but
this tends be problematic primarily for objects made from conductive materials that have
elongated shapes such as leads, guide wires, and certain types of catheters (e.g., catheters with
thermistors or other conducting components).
Notably, more than 30 incidents of excessive heating have been reported in patients undergoing
MR procedures in the United States that were unrelated to equipment problems or the presence
of conductive external or internal implants or materials [review of data files from U.S. Food and
Drug Administration, Center for Devices and Radiological Health, Manufacturer and User Facility
Device Experience Database, MAUDE, http://www.fda.gov/cdrh/maude.html and U.S. Food and
Drug Administration, Center for Devices and Radiological Health, Medical Device Report, (http://
www.fda.gov/CDRH/mdrfile.html)]. These incidents included first, second, and third degree
burns that were experienced by patients. In many of these cases, the reports indicated that the
limbs or other body parts of the patients were in direct contact with body radio frequency (RF)
coils or other RF transmit coils of the MR systems or there were skin‐to‐skin contact points
suspected to be responsible for these injuries.
MR systems require the use of RF pulses to create the MR signal. This RF energy is transmitted
readily through free space from the transmit RF coil to the patient. When conducting materials
are placed within the RF field, the result may be a concentration of electrical currents sufficient
to cause excessive heating and tissue damage. The nature of high frequency electromagnetic
fields is such that the energy can be transmitted across open space and through insulators.
Therefore, only devices with carefully designed current paths can be made safe for use during
MR procedures. Simply insulating conductive material (e.g., wire or lead) or separating it from
the patient may not be sufficient to prevent excessive heating or burns from occurring.
Furthermore, certain geometrical shapes exhibit the phenomenon of "resonance" which
increases their propensity to concentrate RF currents. At the operating frequencies of present
day MR systems, conducting loops of tens of centimeters in size may create problems and,
therefore, must be avoided, unless high impedance is used to limit RF current. Importantly, even
loops that include small gaps separated by insulation may still conduct current.
To prevent patients from experiencing excessive heating and possible burns in association with
MR procedures, the following guidelines are recommended:
Expression MR400 Instructions for Use Guidelines and References E‐1
Guidelines and References