Magnetic Effects

Douglas Rand drand at sgi.com
Mon Mar 3 20:28:15 EST 1997


Adam Reed wrote:
>...
> The information that I gathered about the Gamma radiation being
> produced from the body during a MRI came from consultation with Dr.
> Emanuel Kanal, Associate Professor Department of Radiology at the
> University of Pittsburgh Medical Center.  He does have a website at
> http://kanal.arad.upmc.edu/mrsafety.html

Good web site.  No mention of gamma radiation.  He does mention RF
injury,  which at least makes sense.  Perhaps you are somehow 
confusing gamma radiation with RF?  RF is certainly given off in small
amounts,  that's how MRI works.

> He does agree that gamma radiation is given off from the body and that
> there is a slight increase in the core temperature in the body of the
> patient as a result of the MRI.  He does not feel the there is
> sufficient amount of gamma radiation production to be of any harm
> however, none the less, there is gamma radiation production.

Look,  whether he was polite to you or not,  he's correct and you
are not.  There isn't any gamma radiation produced directly from
the MRI scan.  I suppose that the rate of decay of C14 or some other
slightly unstable isotope might change in the magnetic field,  I can't
imagine this is a serious concern.  Heating would be more significant. 
Perhaps you can quantify this?  

Like I mentioned,  gammas are produced from nuclear interactions and
energy changes such as nuclear decay, particle anihilation and such. 
x-rays are produced from electron energy changes such as inelastic
interaction between electrons and matter, normally bremsstralung (sp?
German for breaking radiation).  Neither of these appears relevant to
MRI technology where rf is produced.  

Doug
-- 
Doug Rand				drand at sgi.com
Silicon Graphics/Silicon Desktop	http://reality.sgi.com/drand
Disclaimer: These are my views,  SGI's views are in 3D



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