Info requested on Neuroimaging

Luke Sjulson luke.sjulson at jhu.edu
Thu Oct 29 09:50:57 EST 1998


> High-resolution, you mean in space. In time it is not so good, due to the
> fact that the hemodynamic response takes about 3 seconds. With EEG and MEG
> you have millisecond resolution, so this is in time better. You can select
> which response you want to localize on.

	A neuroradiologist told me once that sometime in the next few years,
fMRI is going to be done by imaging intracellular vs. extracellular
sodium ions, which will remove this time lag.  It's a lot easier to get
a strong signal from protons, and it is probably very difficult to
distinguish intra- and extra-cellular from chemical shift (when it's
chemical shift coming from atoms that aren't even in the same molecule),
so my uninformed speculation is that the techniques they come up with
might require high-budget specialized magnets, not the kind you find in
most hospitals.  One thing of interest is that this technique would
directly image neural activity, not blood oxygenation levels or
something thought to correlate with neural activity...

> There are efforts on the way to combine both techniques. They may supplement
> each other. Some go even so far as to measure the EEG in the MRI scanner,
> during an fMRI experiment.

	I've heard of that, but I didn't realize they did them both at the same
time.  I wonder how they keep the two from interfering with each other?


Luke Sjulson
luke.sjulson at jhu.edu



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