Who should not get a functional magnetic resonance imaging (fMRI) scan?

Answer: Anyone who is claustrophobic or has magnetosensitive implants should not get an fMRI scan.


Current fMRI machines require the patient to lie down on a platform that is then inserted into a small tunnel for scanning. The tunnel may only be a couple feet wide in diameter. If the patient has a history of anxiety related to claustrophobia, they may be given sedatives before scanning.

FMRI uses strong magnetic fields to determine brain blood flow. The magnetic field generated by an fMRI machine may be several orders of magnitude stronger than the magnetic field of the earth. The large diagnostic fRMI machines may use magnets as strong as 1.5 to 3 Tesla. Because the magnetic field is so powerful, patients with magnetosensitive metallic implants are not candidates for fMRI scans. Common metallic implants include brain aneurysm clips and cochlear implants.

The function of implanted medical devices such as pacemakers or insulin pumps can be disrupted by the magnetic fields. As a result, patients with these devices are not allowed in an fMRI machine.

If there is a risk that the injury is a result of metallic shrapnel, any foreign metal objects in your body may become magnetized and cause internal damage.