Because MRI uses low-energy, non-ionizing radio waves, there are no known risks or side effects. In fact, since the technique uses no radiation, it can be repeated with no known adverse effects.
While there are no known hazards, MRI is not proven to be safe during pregnancy. If a pregnant woman must undergo an MRI, she will be asked to sign a special consent form.
The magnet at the center of the procedure may affect, or be affected by, any person fitted with a pacemaker, hearing aid, or other electrical device. People with such devices should advise the physician or technician. They are generally advised not to have an MRI."
The Food and Drug Administration1 recently reclassified themagnetic resonance imaging (MRI) scanner from a class III toa class II device and issued revised guidelines for the safeclinical use of this imaging modality. Along with the reclassification,the previously recommended conservative levels of exposure tothe electromagnetic fields required for MRI were relaxed significantly.
The new recommended safe levels of exposure are as follows:static magnetic fields, 2 T; gradient magnetic fields, 6 T/sor less; and radiofrequency magnetic fields, exposure shouldnot produce a core temperature increase in excess of 1°Cor localized heating to greater than 38°C in the head, 39°Cin the trunk, or 40°C in the extremities.
No long-lasting, hazardous biologic effects have been observed,and none are anticipated from acute or short-term exposuresof humans to the static magnetic fields currently used in commerciallyavailable MRI scanners.2-4