Patent ID: 9651701
Date: 2017-05-16
CPC Classifications: G01P,G01R,G01V

Claim:
1. An arrangement for association with an operable MRI apparatus located within a room that has an access opening and with the MRI apparatus providing a residual magnetic field that extends to a location of the access opening, and for detecting presence of ferrous material and discriminating out far field magnetic disturbance, the arrangement including: a detector configured to passively monitor the residual magnetic field at the location of the access opening, the detector including an array of magnetic field sensors arranged about the periphery of the access opening in a spaced arrangement such that each sensor is associated with a different portion of the access opening, the magnetic field changing in response to a presence of ferrous material at the access opening, the magnetic field also changing in response to a far field magnetic disturbance, each of the sensors being configured to output a signal having a value indicative of the sensed magnetic field at the associated portion of the access opening; a corrector configured to correct each signal value from the change in response to the far field magnetic disturbance and to provide respective corrected signal values; and a processor configured to use the corrected signal values to determine a ferrous-indicating limit is exceeded and to provide a safety response that addresses the ferrous-indicating limit exceed condition.