A volume from the middle of a time series would be a better reference. If you
know that the first volume selected is going to be the reference image, then
you can select a middle image first.
Best regards,
-John
> If my understanding is correct, SPM realigns a time series of 3D images
> to the first of the series during motion correction. I have never
> thought this reason seriously but our reviewer raised a question and
> suggested that the middle volume is preferable to minimize the additive
> motion artifacts over scans.
>
> Dose anybody know reasons why the first image is chosen as a reference
> in default?
> I am sorry if this issue has already been discussed in this mailing
> list.
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