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Re: MRI and gadolinium



Ed,
It is the latter - "listening" to the decay of radiation
stimulated by a primary pulse. There are many variations on this theme.
But it is not mere absorption, as with X-Rays. (Consider that the RF
wavelengths used are of the orders of meters - yet resolutions less than
a mm are achieved - quite a unique imaging process! The secret is in the
spatial encoding of signal origins through a spatially controlled
magnetic field [which determines the resonant frequency])

A quick search found an MRI tutorial at
http://128.227.164.224/mritutor/index.html
Hope this helps, - Bob

Bob Sciamanda
Physics, Edinboro Univ of PA (ret)
trebor@velocity.net
http://www.velocity.net/~trebor

-----Original Message-----
From: Ed Schweber <edschweb@ix.netcom.com>
To: phys-l@atlantis.uwf.edu <phys-l@atlantis.uwf.edu>
Date: Wednesday, August 19, 1998 10:20 AM
Subject: Re: MRI and gadolinium
. . .
As long as wer're talking about MRIs -perhaps another question. I
have
heard both that the image formation is based on the amount of EM
radiation
absorbed (as with an x-ray) and also that the image is formed by the
re-emitted radiation after the external pulse ends. Does anyone know
which
is the case? Thanks.

Ed Schweber