DOTmed News: How exactly does the FerroGuard System work?

Keene:One has to appreciate that only things made out of steel get pulled into the magnet – things made out of aluminum or copper or brass are not attracted to magnets at all. One needs to make a detector that only detects steel. The FerroGuard System has some magnetic sensors in it and those sensors monitor the ambient magnetic field.


In an MRI machine, that magnetic field is a combination of the earth’s own magnetic field plus the magnetic field of the magnet. Those two magnetic fields are very stationary. But if you bring a piece of steel into those fields, the magnetic field will bend around that piece of steel. FerroGuard looks at changes in the ambient magnetic field, which are caused by ferromagnetic objects passing.

DOTmed News: How sensitive is FerroGuard’s detection of potentially dangerous objects?

Keene: The FerroGuard System has adjustable sensitivity, according to a hospital’s requirements. For example, if it’s set at a maximum sensitivity, it can even detect the ink that’s in a one-dollar bill, because the ink in a one-dollar bill has ion particles in it.

Some hospitals like to have it set quite insensitively, so it just alarms on big objects, like if one were taking a regular gurney, as opposed to an MRI-safe gurney into the room. Some hospitals just like to catch the very big objects.

DOTmed News: How many FerroGuard Systems are currently in use?

Keene At the moment, there are hundreds of systems deployed in the U.S., Europe, Asia and Australia, which is actually a quite small proportion of the total number of MR machines in the world. But that’s because this is a new technology and not everyone has heard of it yet and not everyone has seen the need.

The U.S. is leading the way with this because it’s the first nation to really recognize that it’s really a problem and that there is a now a technical solution to that problem. The invention of the technology has generated a new market but because it’s a new technology, it’s not completely spread worldwide but it’s growing at a very rapid rate.

DOTmed News: You said the U.S. is leading the way in MRI safety – what about the UK imaging community?

Keene: It’s growing but we do not have any official regulatory bodies mandating the use of magnetic detection systems yet. I think this is because in the U.S., hospitals are generally private entities that are competing against one another and there are also issues with insurance. In the UK, the National Health Service is a state-owned health care system and so it has different drivers. I’m sure that these systems will become mandatory in the UK and all of Europe [in the future].

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