Originally posted by humy
but a Faraday Cage cannot be used for peacetime medical scanning.
A faraday cage holds off only electric fields. You could make something similar for magnetics if you used Mu-metal, which conducts magnetic field lines into itself and shields something from the magnetic field, but I have no idea how thick such metal would have to be to make a good shield big enough for the human body. Obviously it would be more than 2 meters long and a meter wide and high for use on humans.
It might also be possible to make a repelling shield similar to noise cancelling earphones for audio. You could see series of magnetic sensors coupled with reverse field coils that could null out external fields.