Dear ALL,
The general consensus is stent wearers should stay out of the 5G lines at least for year, while the stent "grows" in. All people wearing stents should consult the vendor and /or their physician. Certain stainless steel might be okay, but this depends on how the stent is inserted. The two concerns about stents include movement of the stent and eddy currents causing local heating and therefore increased drug release, if the stent is coated or burns. One survey of people, who wore stents, but still had MRIs, showed little or no movement of the stent. This could be time related as there is a "grow" in time. I've added some of your helpful summaries below.
Thank you to all of you,
Martha
________________________________________________________________
Nearly 4 years ago I had a stent fitted in my right coronary artery following a heart attack - from what you've said it sounds like the same type of stent, a drug eluting one. These are relatively new tech, when I explained my work with powerful magnets to my consultant he stated that ' he didn't have figures for the drug eluting stents, but that typically a normal stent would be expected to have 'grown in' to the epithelial cells after 6 months - making the stent safe for MRI. In my case he erred on the side of caution and banned me from anywhere closer than the 5 Gauss line for a year!
Since then - nearly 3 years now - I have regularly been in close proximity to all our magnet systems (I guess the most intense field I've experienced is probe changes on our 400 & 500 systems) - so far the stent hasn't dislodged, and barring initial trepidation, no adverse effects.
_______________________________________________________________________________
I'm not sure whether this helps or not, but our safety document has a
general statement saying that Objects and people at risk from the
magnetic field are considered safe outside the 5 gauss line (i.e. in
magnetic fields smaller than this).
For any mechanically activated implant (e.g. pacemaker) this is
important in order for it to be able to operate correctly. For
"passive" implants the risk in the magnetic field is of it being moved
or dislodged. Certainly 5 gauss would be safe, but it is likely that
higher magnetic fields would be fine. The only relevant article that I
found on the internet was the one attached. This information is
obviously specific to the device used.
http://cat.inist.fr/?aModele=afficheN&cpsidt=18909271 <
https://exchange.uconn.edu/exchweb/bin/redir.asp?URL=http://cat.inist.fr/?aModele=afficheN%26cpsidt=18909271> (I found this link particularly helpful.)
I would recommend that the user should contact the manufacturer of the
stent, and ask them for a guideline of field strength that it is safe to
be within. Once he has this information, if it is one of our magnets,
we would be able to provide him with a plot of the "safe field" region.
_________________________________________________________________
About the thing below.....the stent should be made of 316 so not magnetic but apparently the concerns with coated stents and MRI's is: stent migration (especially after its just been put in), localised heating which will increase the elution rate of the rapamycin from the stent and the stent causing artifacts in the MRI. Obviously the last is not an issue for NMR but the first two may be a concern. However these probably won't be an issue after a while once all the rapamycin is gone and the artery has healed. But best thing to do is contact the stent manufacturer (its probably a Johnson & Johnson Cypher stent?) for their advice.
____________________________________________________________________
If he cannot have an MRI, then he cannot go near the NMR magnets, which are at much higher field. How close he can get to the magnet is a matter of opinion.
We recently heard a medical doctor claim that a stent should be okay because it's 'nonmagnetic' but he immediately added that he wasn't certain. The problem is that 'non-magnetic' stainless steel becomes magnetic if it's worked (drilled, shaped, etc). The stent is inserted into the body in a collapsed state and then reshaped to form a cylinder by inflating a balloon inside the stent. This reshaping increases the magnetic moment by at least an order of magnitude. The only way to make it 'nonmagnetic' again (actually with a very low magnetic moment) is to anneal it and the human body is not compatible with the annealing temperature! Don't go near the magnet if you have a steel stent inside your body.
____________________________________________________________________________
You need more information. The statement that he can not have an MRI
could stem from a variety of things. It could be that the applied RF
will heat the stent causing burns. It may be that the stent, while
nonmagnetic enough that the forces are minimal, it may cause huge
distortions in the image. It may be the stent is magnetic. This
last case is the one that concerns you. My guess (and only my guess)
is that he can not have an MRI because of the RF. You should find out
the variety of Stainless Steel to find out if it is magnetic. Some
Stainless Steels are and some are not. In particular 300 series (304,
316, 321, etc.) Stainless Steels are not magnetic.
Martha Morton, Ph. D.
University of Connecticut NMR Facility Scientist
Chemistry NMR Lab Director
(860)486-4069
Received on Wed Jan 07 2009 - 06:25:11 MST