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5 gauss line

Last revised by Dr Yusra Sheikh on 28 Oct 2021

The 5 gauss line is the safety line drawn around the perimeter of the main magnet of the MRI scanner, specifying the distance at which the stray magnetic field is equivalent to 5 gauss (0.5 mT).

Five gauss and below are considered 'safe' levels of static magnetic field exposure for the general public.

At 5 gauss and above:

  • cardiac pacemakers and other implanted electronic devices are at risk of being interfered with by the static magnetic field
  • ferromagnetic materials may become projectile (and are thus prohibited from crossing the 5 gauss line)

Note that the distance at which a 5 gauss line is drawn around a particular MRI scanner will depend on magnet strength and the level of magnetic shielding used.

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