Magnetic Effects of MRI

Jonathan Jones jajones at ermine.ox.ac.uk
Tue Mar 4 08:16:04 EST 1997


(Newsgroups line trimmed somewhat...)

In article <331B164D.2CEB at mail.delcoelect.com>,
John D. Borneman <jdbornem at mail.delcoelect.com> wrote:
>I am forwarding this thread to sci.techniques.mag-resonance.  This group 
>represents the scientific community on all types of MRI issues.  
>Hopefully, an informed member of that group will help out with some 
>facts
>
>Adam Reed wrote:
>> 
>> There does seem to so question as to the effect of magnetic imaging.  Just
>> try and get an MRI on a pregnant women.  All the MRI facilities in my area
>> refuse to do one on a pregnant patient and the reason that was given was
>> that "they do not know the long term effects of the MRI."  There seems to
>> be a question as to gamma radiation being produced from the patient during
>> an MRI.
>> 
>> Achim Recktenwald, PhD <achim at ibex.ca> wrote in article
>> <33119347.2596 at ibex.ca>...
>> > W.E. Chan wrote:
>> > >
>> > > What are the effects of a strong magnetic field on the human body?
>> > >
>> > > Erwin Chan
>> >
>> > Since I never heard of any negative side-effects of Magnetic Resonance
>> > Scanners on humans, I assume nothing serious.

Any suggestion of gamma ray production is complete nonsense.  Beyond that
there is no evidence whatsoever that MRI has any long term effects.  It
can't be ruled out completely, but given the large number of MRIs which
are done every year, it clearly can't be that dangerous or somebody
would have spotted something by now.  The only dangers currently
known about are the effect of the high magnetic field on cardiac pacemakers
and on other implanted ferromagnetic items (such as surgical clips, or
shrapnel).  Screening patients for these items is of course vital.

In the UK MRIs are not usually used during pregnancy, but there is no
particular reason for this; it's just an example of the usual medical
paranoia which forbids all sorts of treatments to pregnant women.  My
wife, who is a researcher in MRI/MRS, provided control spectra throughout
her pregnancy, as well as a number of images.  Our son seems healthy
enough.

As a side issue it should be noted that MRI presents a number of other
issues beyond the safety of magnetic fields, in particular the presence
of RF and audiofrequency oscillating magnetic fields from the gradients.
IMHO in the event that any safety implications *are* discovered, they
will probably be linked to these rather than to the magnetic field
itself.

Finally, please note that sci.techniques.magn-resonance is intended for
the *whole* of magnetic resonance, and not just the MRI/MRS portion.
Postings on high resolution or solid state NMR, or on ESR, or even on
NQR, are welcome here.

Jonathan




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