John-- thank you for your help; I am sorry to be so concrete, but I want to
be sure I'm straight on this:
1. in the cae of PET/SPECT, the "reference image" is the mean image
calculated on the first pass
2. the default setting is NOT to weight this image
3. one cannot choose another image, since this is data-derived, reflecting
variance -StdDev, really-- at each voxel
in my case, I am aligning 2 or 3 images per subject, so I conclude this
option would not help me, as the voxel varainces would not be a useful
index of anything. Do you agree?
also-
when you say "fix this", are you referring to Realign or Spatial? fix to
which, var or SD? why ?
>on the estimated parameters. The weighting procedure uses an image
>which can contain zeros and ones, or more properly, it can be thought of
>as containing the reciprocals of the standard deviation at each voxel
>(unlike weighting in the spatial normalisation where the weight is
>the reciprocal of the variance - I must fix this).
many thanks again
********************************************************
Christopher Gottschalk, MD *
Assistant Professor of Neurology & Psychiatry *
Yale School of Medicine *
*
Mailing Adress: *
VAMC [116-A] tel [203] 932-5711 x4329*
950 Campbell Avenue FAX 937-4791*
West Haven, CT 06516 *
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