Talk:Magnetoencephalography

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[edit] infinate solutions

Is wrong I don't have the time to edit it now but the VARETA algorithm developed by E.R. John was designed to allow for source localization, which is later z normed. —Preceding unsigned comment added by Androm (talk • contribs) 17:23, 6 May 2008 (UTC)

[edit] MEG images produced

What type of images do these MEG's produce? Can anyone in the field post one?

MEG's don't produce images directly. They generate data points which can be plotted on a DICOM image such as an MRI. Here is an example from the 4D Neuroimaging's website (they manufacture these devices) http://4dneuroimaging.com/images/MEG_Work_4.jpg These images represent brain functions such as language centers or motor/sensory function areas in the cortex. It is also valuable for localizing epileptiform (i.e. seizure foci) activity. With this information, a neurosurgeon has a better view of which portion of cortex is functional (i.e. should be preserved) and which is diseased and should be resected (seizure focus, tumor, etc.). The difference in location may be millimeters.

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Actually, some methods attempt try to produce the image of the current in different parts of the brain. One example is http://www.kolumbus.fi/kuutela/mce/mce.gif However, there is no general "format" for this kind of images, and every application uses their own way of visualizing the estimated currents.

KUutela 20:26, 7 February 2007 (UTC)

[edit] Infinite solutions

I've read about other inverse problems having an infinite number of solutions, but this is often extremely misleading, such as the failure to include in the model critical domain constraints. In this case, a domain constraint could be that the solution corresponds to a physical possible vascularization although in this case MEG doesn't seem to be much coupled to blood flow patterns.

Another case is that the "infinite solutions" correspond to a probability distribution produced by the same model which defines a finite entropy.

A final case is that the infinite solutions correspond to fussy details no one actually cares about, while features of primary concern are fixed uniquely.

What the lay person rarely understands when they encounter the phrase "infinite solutions" is that this generally translates to "unfortunately, we weren't able to come up with an equation that entirely spares us from the [socially contentious] application of common sense". MaxEnt 15:32, 6 January 2007 (UTC)

Unfortunately in the case of MEG/EEG, some of that space of potential solutions is of practical import. For instance, Irina Gorodnitsky showed some time ago that, given finite resolution etc, a more focal deeper source produces the same measurements as a less focal more shallow source. Barak (talk) 21:20, 18 November 2007 (UTC)