The operating modes for MR systems as defined by the International Electrotechnical Commission (IEC) are, as follows:

NORMAL OPERATING MODE- mode of operation of the MR equipment in which none of the outputs have a value that may cause physiological stress to patients. (Note: The default specific absorption rate (SAR) level is 2.0-W/kg.).

FIRST LEVEL CONTROLLED OPERATING MODE- mode of operation of the MR equipment in which one or more outputs reach a value that may cause physiological stress to patients, which needs to be controlled by medical supervision.(Note: The default specific absorption rate (SAR) level is 4.0-W/kg.)

SECOND LEVEL CONTROLLED OPERATING MODE- mode of operation of the MR equipment in which one or more outputs reach a value that may produce significant risk for patients, for which explicit ethical approval is required.