In my honest opinion, all subjects need to be processed the same way.
If you have 2 scans, you could use the suggested approaches, or you
could coregister them, then average them in. After averaging , you can
do the rest of the processing.
Averaging should give similar as increasing the NEX.
On Thursday, May 19, 2011, Jonathan Peelle <[log in to unmask]> wrote:
> Dear Steven,
>> We are comparing two groups of 13 subjects with DARTEL VBM8. I know this
>> is underpowered, but wondered if there is any way to use the multiple T1
>> images that were acquired for some of the subjects (in the same session). My
>> initial thought is to process all T1s and use the quality check to see if
>> there is a "better" image when I have two for a given subject. Are there
>> better ways to use multiple T1s?
> In the "new segment" option in SPM8, you can specify multiple
> modalities of images for segmentation. I assume you could also
> provide SPM with 2 T1 images. SPM will then use the combined
> information across images to assign tissue class probabilities, and in
> general I would think that more data would provide a more accurate
> result. However, I think you'd want to process all of your subjects
> the same way. So if you only have multiple T1s for a subset, I would
> probably stick with the approach you suggest—see if you can identify a
> "better" image. (Or, if this is hard to determine, then just use the
> first.) But if anyone else has alternate approaches, I'd be very
> interested to hear!
> Best regards,
Best Regards, Donald McLaren
D.G. McLaren, Ph.D.
Postdoctoral Research Fellow, GRECC, Bedford VA
Research Fellow, Department of Neurology, Massachusetts General Hospital and
Harvard Medical School
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