Kenneth Sharp-Knott via groups.io schrieb:
The question has come up recently in our facility if there is
any concern for users of NMRs with IUD's. We have one older
Oxford magnet that is the only one with a significant fringe
field.
My limited 'research' indicates that most IUDs are safe for MRIs
with the exception of stainless-steel IUD's.
Does anyone have any further information specific to NMR use?
Hi Ken,
users should have an "implant pass" which states the maximum allower
magnetic field.
For modern implants (pacemakers, cochlea implants, insulin sensors/pumps) the limit
is typically 1 T or higher. One definitively needs to check this
before deciding!
In a similar case, I therefore measured the stray field on our two old unshielded magnets,
an Oxford 500 (built 1988) and a Bruker 900 (1995). Surprisingly, on the surfaces of the
500 magnet I found ca. 0.3 T or less, which also coincides with stray field calculations
(based on an ideal dipole) I made a few years ago. 1 T would only be reached at the
bottom plate of the magnet, which is not accessible due to the built-in cryoprobe.
For the 900, stray fields are naturally much higher, are still below 1 T on the platform that users
climb to manually exchange samples (we don't have a sample case to so). This is probably
due to the much larger dimensions of the magnet dewar (it's a 2 K magnet), which sterically
prevents people from getting closer to the coil.
However, here access to the bottom region of the magnet is not recommended or such people,
but thanks to ATMA is completely unnecessary for normal users
(except for magnet maintenance).
So I gave that person permission to use both magnets (esp. since the implant pass stated
3 T as the limit).
Greetings from Euromar,
Gustav
--
PD Dr. Gerd Gemmecker
Bayerisches NMR-Zentrum
NAT School, TU München
Lichtenbergstr. 4
D-85747 Garching
Germany
Raum/Room 2108 / BNMRZ, E.O.Fischer-Str. 2
Tel. +49 (89) 289-52604
Fax +49 (89) 289-52669
e-mail: Gerd.Gemmecker_at_ch.tum.de
Internet: http://www.gemmecker.de
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Received on Mon Jul 07 2025 - 07:15:16 MST