They look pretty similar to me. A difference of about 0.0000000000000001 is
pretty small really, and is attributable to rounding errors. Try evaluating
the following in MATLAB:
1.0000000000000001 - 1
On Tuesday 24 March 2009 19:04, Xu, Ben (NIH/NINDS) [E] wrote:
> I have a question about the realignment parameters saved after
> performing "Realign and Unwarp" with SPM5.
> I realigned two sessions (i.e., scan runs) using the default setting
> with the first image of the first session as the reference image. I
> performed realignment in two ways:
> Method 1: Included all the volumes in both sessions.
> Method 2: Included only the first volume for the first session (Session
> 1), but all the volumes in the second session (Session 2).
> I was expecting the realignment parameters for Session 2 to be identical
> or near identical with both realignment methods. However, this is not
> what I got (see attached image). With Method 1, the realignment
> parameters for the first volume (row 1 in the upper table of the
> attached image) are almost all 0s except for the second column. But,
> with Method 2, the realignment parameters for the first volume (row 1 in
> the lower table in the image) are quite different from the results of
> Method 1, although the rest looked almost identical. Why is there such a
> difference for volume 1? Is it expected?
> Thanks much for your help.
> -----Original Message-----
> From: John Ashburner [mailto:[log in to unmask]]
> Sent: Tuesday, March 24, 2009 1:57 PM
> To: [log in to unmask]
> Subject: Re: [SPM] Dartel Normalization of fMRI data
> If you have SPM8b (latest updates), then you should find this much
> easier, as there is now an option to spatially normalise (and spatially
> blur) fMRI to MNI space (as it incorporates an additional affine mapping
> between DARTEL template and MNI template). I haven't had a chance to
> update the user guide for DARTEL yet, but it should be reasonably
> straightforward to use.
> I expect that the t stats should be increased, and look forward to any
> feedback on whether this is the case.
> Best regards,
> On Tuesday 24 March 2009 16:22, Amir Tahmasebi wrote:
> > Dear John and SPMers,
> > I am trying to use DARTEL for normalization of fMRI data. I have
> > looked at "how to use DARTEL for normalizing fMRI con maps?" thread
> > but it is not exactly what I was looking for.
> > I was wondering how should I use the outputs of DARTEL ("u_rc1*.nii"
> > and
> > "Template_6.nii") to normalize my fMRI data which is already
> > coregistered to the corresponding structural data.
> > Thank you,
> > Amir