Mark Keene is a specialist in high sensitivity magnetic sensors and systems, and for the past five years, his expertise has been available to the imaging community through Metrasens Ltd, a company that manufactures MRI safety systems.
Last month, Keene, the chief technology officer with Metrasens, spoke with DOTmed News from a hotel room in Sacramento, Calif., after a flight from the United Kingdom. (He’s the main supplier of magnetic and sensor detection apparatus expertise for the UK’s Ministry of Defense.)
Keene talked about his invention, the FerroGuard System, and the issue of MRI safety in the U.S. and abroad.
DOTmed News: How common are patient or staff injuries as a result of ferromagnetic objects entering the MRI room?
Thankfully, fatal incidents are comparatively rare. There have been about two in the last eight to nine years or so that I’m aware of. But with injuries, there’s a lot more than that. The truth is we don’t actually know how many accidents there are because we feel that about 90 percent of those accidents go unreported. This is because it’s quite embarrassing for a hospital to have an accident.
When we go around and talk to hospitals, we often come across ones that have had a major incident like a gas cylinder, a gurney or a chair go into the magnet and the majority of MRI magnets we’ve seen have had some minor incidents, like a pair of scissors, paper clips or very small objects get pulled into the magnet. These very small incidents are incredibly common and they can injure people. Fundamentally we don’t know [the rate of minor incidents] because there isn’t a requirement for hospitals to report these accidents.
DOTmed News: Metransens offers the FerroGuard MRI system, a visual and audible alarm that alerts staff before ferromagnetic material makes it into the MR room. How did you come up with the idea for FerroGuard?
Throughout my research career, I worked in a big research and development company for the government on submarine and land mine detection. I developed sensor technologies to detect these things.
I was at a conference once in the United States on these subjects and I got back to my hotel in the evening and slopped down in a chair and just put on the TV. At that point in time, a news story was on about a small boy in New York, Michael Colombini, who had died that day. While he was in an MRI machine, somebody took an oxygen cylinder into the room. It got pulled out of the technician’s hands and accelerated into the magnet, striking the boy in the head. He died of massive hemorrhaging. Because of my background in submarine detection, I immediately knew how one could develop a piece of technology that would prevent that accident from happening and that would give a person a warning if they were going into the MRI room with something that is likely to get pulled in.
DOTmed News: How exactly does the FerroGuard System work?
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?
: 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?
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?
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].
DOTmed News: Could even small ferromagnetic objects damage the magnet?
Although the primary goal of FerroGuard is the safety of the patients and staff of the hospital, if small things get into the magnet, it could result in expensive damage. Sometimes the magnet has to be quenched and there’s downtime and costs associated with that.
I was just in a hospital a month ago and they had something go into a machine and it cost $100,000 to sort it out. Even these small to medium-size accidents can cost the hospital a lot of money, much more than the cost of a FerroGuard System to prevent it from happening in the first place.
DOTmed News: In the U.S., The Joint Commission now requires all new MRI suites to have a ferromagnetic detection system in order to be accredited. Do you offer any additional resources for facilities to ensure MRI safety?
Metrasens has produced a guide for architects for new MR installation designs. Because of the recognition of the projectile effect hazard, there’s a lot that can be in the design of the MR suite itself to address the issue and make it much safer intrinsically. We’ve just released a guide for architects on our website with drawings and information on how FerroGuard actually works and how it can be optimized in the new MR design. We’re working with architects to try and keep these new facilities as safe as they can possibly be.
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