[Mristudio-users] motion correction makes sense?

[Durai Arasan]

Hi all,

A general question about motion correction in diffusion imaging. In fmri
this is a commonly practiced preprocessing step where the new signal, say,
F' is obtained by a spatial shift of F, signal acquired when movement
occurred:

F' = F*m

where m = m(x,y,z), the motion matrix.

But in diffusion this is clearly not the case as the signal in each
direction is a function not only of the position of the brain but also of
individual brain geometry. Therefore, new signal D' will be a
*transform*(not shift) of signal D, acquired when movement occurred:

D' = D*t

where t = t(x,y,z,brain_geometry), the transform factor.

So unless there is an estimate of t, I don't think any motion correction is
going to be useful in diffusion, certainly not a simple rigid body
adjustment. Am I wrong?

Thanks
Durai
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