Science informs us ofabout a tricky problem facing Chinese neuroscientists: Fear of MRI Scans Trips Up Brain Researchers.

Apparently, many parents are concerned about the possible impact of strong magnetic fields on children, and are unwilling to allow their children to get MRI scanned for research purposes; the article reports on two Chinese neuroscientists who were unable to find healthy children to volunteer for their MRI studies.

“I would not dare to allow my children to be tested by MRI,” says radiologist Han Hongbin of Peking University Third Hospital. “Nobody can ensure that there is no potential danger,” such as during nonroutine MRI scans that use extremely powerful magnetic fields, he says.

This is not a problem I've heard of amongst Western researchers, but on the other hand, it's not all that bizarre. In Britain, and as far as I know elsewhere too, standard practice is never to include women who are (or might be) pregnant in fMRI studies. This is not because strong magnetic fields have any known risks for unborn babies, or indeed anyone else. It's purely a better-safe-than-sorry precaution. But it sounds as though the concerns of Chinese parents are of that kind as well.

MRI safety is an interesting topic. Used incorrectly, an MRI scanner could, in theory, harm you in quite a few ways, from heating you up due to radiofrequency energy transfer, to stopping your heart by inducing an electric current in it (although I don't think that's ever actually happened, it is a theoretical concern). Fortunately, by sensible selection of the scan parameters, these risks can be avoided.

The only real danger is that posed by metal objects (specifically ferromagnetic ones), which in the presence of a strong magnetic field become deadly projectiles. This is why it's a bad idea to carry that pair of scissors into the scanner room. Remember: the magnet is always on...