Abstract: Safety of MRI for both patients and employees is reviewed. The safety concerns and considerations of exposure to static magnetic fields, radio-frequency fields, switching magnetic field gradients, acoustic noise and image enhanced contrast agents are described. In the absence of ferromagnetic foreign bodies, there is no replicated scientific study showing a health hazard associated with static magnetic field exposure and no evidence for hazards associated with cumulative exposure to the field. In magnetic resonance, time-varying gradient magnetic fields (dB/dt) may stimulate nerves or muscles by inducing electric fields in patients. For gradient ramp duration of less than a few milliseconds, mean peripheral nerve stimulation is a safe indicator of high dB/dt. During an MR procedure, most of the transmitted RF power is transformed into heat within the patient's tissue as a result of resistive losses, and the primary bioeffects associated with the RF radiation are directly related to the thermogenic qualities of this electromagnetic field. During the operation of MR systems, various types of acoustic noise produced, and they may produce substantial hearing problems in patients. The simplest and least expensive means of preventing problems associated with acoustic noise is to encourage the routine use of earplugs. The total incidence of adverse reactions of Gadolinium-based MR imaging contrast agents ranges from approximately 2% to 4%, cautions should be taken during MRI measurement.

Key words: MRI, Safety, Static magnetic fields, Radio-frequency fields, Magnetic field gradients, Acoustic noise, Contrast agents