In article <7unvru$pug at news-central.tiac.net>, Bob <rgsrose at tiac.net>
writes
>Hello:
>>I am wondering if anyone is familiar with the various new "imaging"
>techniques I've heard about such as Positron, etc. that conceivably could be
>used to image/study nerves and (small) facial muscles.
>>I've been told, repeatedly, that MRI cannot be used for nerves and muscles.
>>Thanks,
>Bob
>>I'm not sure exactly what you're after, but I'll try to shed some light.
Positron Emission Tomography (PET scanning) is used mainly to examine
changes in regional cerebral blood flow (rCBF) while people perform "tasks"
in the scanner e.g. looking at pictures, thinking up lists of words, playing
simple computer games, etc. The basic idea is that by getting someone to do
something, and monitoring the blood flow to different areas of their brain
while they do it, you can make inferences about which brain regions are
involved in particular functions. I emphasise *regions*- it's not yet possible
to image individual nerve fibres (or even discrete bundles of fibres). It seems
likely that a newer technique called diffusion tensor imaging may take steps
towards this.
As regards MRI- I think the confusion arises because MRI can be used in
two ways. Structural MRI takes detailed pictures of the brain (or other
organs) but doesn't tell you anything about dynamic function. Generally
when people say "I had an MRI scan", this is the type they're referring to.
But there's also Functional MRI (fMRI), which can measure changes in
regional blood flow, and thus can be used in a similar way to PET (although
the underlying physics is completely different). In fact fMRI gives better
spatial resolution than PET, and one is able to acquire more data per
scanning session with fMRI than with PET.
As regards imaging muscles- MRI is commonly used to image heart muscle,
but I'm not aware of techniques for imaging small facial muscles.
Taking your query about facial muscles together with your post asking for
info on Botox, I think I can guess what the problem is. I really recommend
you look at the Botox website (see my response to your Botox query) as
there's lots of background info there.
With best wishes
--
Nick Medford
