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Dr. Bob is Robert Hsiung, MD,
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Posted by denise1904 on November 24, 2004, at 8:08:43
Hi,
Can someone tell me if there is a scan that shows up neurons in different parts of the brain, I don't mean just levels of activity? Or can they only see neurons in the brain during a post mortem. I'd like to know if I am lacking any specific neurons in any particular area :-)
Also, can somebody eplain simply what the difference is between a Pet, Spect and fMRI?
Thanks........Denise
Posted by SLS on November 24, 2004, at 11:20:03
In reply to Scans, Pet, Spect and fMRIs?, posted by denise1904 on November 24, 2004, at 8:08:43
Hi Denise.
I'm not sure about all of this, but I'll take a shot at it.
A regular MRI resolves brain structures, mapping the gross topology of the brain. The images display the brain as it exists in one moment of time. If you are "missing" significant amounts of brain tissue, it should show up in the image. However, I don't think a MRI can resolve smaller brain circuits, even though significant numbers of neurons might be absent. For now, neurons at this level are best determined by their activity, which requires dynamic measurements.
SPECT and fMRI rely on the measurement of blood flow to produce an image. Blood flow is an index of neural activity as the active neurons require more oxygen and thus more blood. PET, on the other hand, is an index of molecular binding or metabolism. It can determine the activity of neuronal tissue by measuring the uptake of radiolabelled glucose (flouroxydeoxyglucose). Using other types of radiolabelled molecules known to be ligands of specific receptors, PET can determine the density and location of those receptord. PET can produce images of greater resolution than SPECT, but is very much more expensive to implement.
MRI - density of water in tissues
fMRI - density of water molecules in oxygenated blood within the blood stream.
SPECT - density of radioactive decay of tracer elements within the blood streem.
PET - density of radiolabelled glucose molecules accumulated in within neurons.
- Scott
Posted by pablo1 on November 24, 2004, at 11:43:17
In reply to Scans, Pet, Spect and fMRIs?, posted by denise1904 on November 24, 2004, at 8:08:43
PET scan: http://www.radiologyinfo.org/content/petomography.htm
Sounds just like SPECT scan from what I understand using radioactive injection then tracing blood flow. I read somewhere that fMRI also traces blood flow but is much more detailed than PET. MRI uses a big magnet to get very detailed slices through you, as I understand it's as good as dissecting a corpse. Regular MRI is more like a regular photograph, fMRI (functional MRI) is different in this way:
http://www.fmrib.ox.ac.uk/fmri_intro/
"FMRI is a technique for determining which parts of the brain are activated by different types of physical sensation or activity, such as sight, sound or the movement of a subject's fingers. This "brain mapping" is achieved by setting up an advanced MRI scanner in a special way so that the increased blood flow to the activated areas of the brain shows up on Functional MRI scans."So I think a conventional MRI would provide what you want though I doubt it's detailed enough to spot an individual neuron, it could spot certain parts of the brain being smaller in at least as good of a detail as the naked eye could inspect a dissected brain. fMRI shows whether that part of the brain is actually active during a particular mental activity or state of mind. You may have the meat there but it's not being activated. ADD sufferers experience underactivity in their frontal lobes though their brains look pretty much the same as a normal person's brain.
I just signed up to volunteer for an fMRI study but I suspect they won't accept me because I answered that I had some psychological disorder diagnosis but you never know. There is no way I can pay $5,000 to $10,000 for doing this on my own. I am (considering) paying $3,000 for a full SPECT scan workup including analysis, diagnosis & initial treatment recommendations.
Here's an explanation of SPECT & PET scans though it's not clear to me what the difference is: http://www.spineuniverse.com/displayarticle.php/article231.html
This page gives a similar shorter comparison of SPECT & PET: http://imaginis.com/nuclear-medicine/nuc_pet.asp
They say PET is much more expensive than SPECT.
Posted by crazychickuk on November 24, 2004, at 14:25:36
In reply to Re: Scans, Pet, Spect and fMRIs?, posted by pablo1 on November 24, 2004, at 11:43:17
Posted by denise1904 on November 25, 2004, at 7:20:20
In reply to Re: Scans, Pet, Spect and fMRIs?, posted by pablo1 on November 24, 2004, at 11:43:17
..
This is the end of the thread.
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