Methods are disclosed for non-invasive screening of the human body by rejecting the magnetic response from biological tissues in the region of interest and outputting data corresponding to the magnetic response of a ferromagnetic foreign body within the region of interest....http://www.google.fr/patents/US6496713?utm_source=gb-gplus-shareBrevet US6496713 - Ferromagnetic foreign body detection with background canceling
Ferromagnetic foreign body detection with background canceling