I don't think it's a problem. I've done it once or twice. As long as your subject doesn't have a TBI or stroke or some other major issue, I doubt you would see any difference between the T1's a week apart. You might as well save those 5 minutes for another fMRI run.

On 02/05/2014 01:11 PM, Colin Hawco wrote:

Hello all, 

I am planning an imaging study which involves 2 sessions separate by about a week. In the first session we collect a nice high res anatomical T1 scan. For the second session, the emphasis is on the task based fMRI. 

At present I am using my T1 for image registration/normalization. Hiwever, in the current design, I want to maximize my time in the scanner and number of trials in fMRI. So I hope to avoid a repeated T1 scan. 

Is there any issues with using a T1 scvan from an earlier session (e.g. 1-2 weeks previous) to calculate the normalization parameters (I am using segmentation for this, as suggested in the SPM8 manual in the examples)? Will running co-registration on the T1 be sufficient? 

It is worth noting there may be differences in head position and angle due to the nature of the second scan.  

Thanks : )

Colin