MRI safety

Unlike other imaging forms like X-rays or CT scans, MRI doesn't use ionizing radiation. MRI is increasingly being used to image fetuses during pregnancy, and no adverse effects on the fetus have been demonstrated, Filippi said.

Still, the procedure can have risks, and medical societies don't recommend using MRI as the first stage of diagnosis.

Because MRI uses strong magnets, any kind of metal implant, such as a pacemaker, artificial joints, artificial heart valves, cochlear implants or metal plates, screws or rods, pose a hazard. The implant can move or heat up in the magnetic field. 

Several patients with pacemakers who underwent MRI scans have died, patients should always be asked about any implants before getting scanned. Many implants today are "MR-safe," however, Filippi said.

The constant flipping of magnetic fields can produce loud clicking or beeping noises, so ear protection is necessary during the scan.