Hi All,
I have received 14 replies and at least as many "out of office" auto replies. There was a number of requests for a summary, which I provided below.
Most stated the obvious that the field strength inside a 7T MRI would be far greater than any stray field a user would experience operating an NMR instrument, and concluded that my user would be fine. But there were four who suggested caution, and I quote them below:
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My understanding is that your user can be imaged (placed in a field) that is no larger than 7.0 Tesla (300 MHz proton).
You are probably asking him to work inside the 5 Gauss line, perhaps allow him to approach a non-shielded magnet and so be exposed to the fringe field in close approximation at the top of the solenoid. This field is probably no greater than 1 Tesla or so on any magnet up to 600 MHz, less if the magnet is actively shielded.
You can ask the solenoid manufacturer for a plot of the fringe field for the magnets this user will approach and then set guidelines accordingly.
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My suspicion is yes, but ask the manufacturer.
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This really should be clarified with the paper work provided the the bearer of the implant. If it is truly a MRI 7T limitation, you will have no ill effects up to a 7 Tesla field strength; quite frankly, you'd have to be in the bore to be exposed to that strong a field. But having read into it a bit, there is an MRI conditional #7, that is not completely related to the field strength. There are other considerations that need to be taken into account besides field strength. So, my recommendation is to seek the documentation provided with the implant procedure to be sure.
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In theory it should be safe up to 7T (of course safe for 10gauss, 10gauss=0.001Tesla).
I'd suggest asking the user get written clearance for his/her doctor to be on the safe side, 10/5gauss line is clearly marked... Recently we have someone, who has an implant MRI conditional to 3T, felt uneasy and faint near 10gauss line. Thorough investigation/medical exam of the accident suggested the cause is not related to the implant ...
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I think the voices of caution raised a valid question - should we as NMR lab managers make this kind of decision, or should we leave the decision to the doctors and/or device manufacturers?
Thanks again to all who replied.
Feng
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From: Feng Lin
Sent: Monday, October 3, 2016 12:48 PM
To: 'ammrl_at_ammrl.org'
Subject: Question on "MRI conditional" metal implant
Hi All,
We have a user with a metal implant that is MRI conditional to 7.0 tesla or less. Does anyone know how that translates in the NMR environment, i.e., safe outside of the 10 or 5 Gauss line? Thanks.
Feng
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UT Southwestern
Medical Center
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Received on Wed Oct 05 2016 - 05:56:56 MST