Did you delete the .mat files of the original images before running
the realignment a second time? The different starting estimates may
produce tiny differences between the final results.
Apart from this, I can't think of another explanation.
All the best,
-John
| I want to run realign by-passing the spm-user interface (for possible
| automation). First I use the spm interface (PET/SPECT).
| realign
| number of subjects: 1
| then I selecte the two files (longitudinal studies from one
| person)
| Coregister & Reslice
| Sinc Interpolation
| All Images (1...n)
|
| The generated r*img (hdr, mat) files are then renamed as spmr*.img (hdr
| mat),
|
| In running above, I find that
| flagsC.quality=0.5
| flagsC.fwhm = 8
| flagsC.rtm =[]
|
| and
|
| FlagsR.hold=-9;
| FlagsR.mask=1;
| FlagsR.which=2;
| FlagsR.mean=0;
|
|
| then, I just run
| spm('pet');
| global MODALITY SWD
| SWD=spm('Dir');
| MODALITY='PET';
| %the above codes may be un-necessary
| spm_realign(P,flagsC);
| spm_reslice(P,FlagsR);
| where P is the 1X1 cell containing the two file names
| to re-generate the r*img (hdr mat) files.
|
| I expect the spm-interface procedure generated r*img should be identical
| to the one generated directly by running spm_realign.m and spm_reslice.m.
| What I found however, they are not EXACTLY identical. The maximue pixel
| value difference, in most slices, is one (should be zero, if identical)
| and in some slice levels, the difference is as high as 10.
|
| Visual examination of the two images could not detect any differences and
| pixel-by-pixel linear regression give almost a 45 degree line.
|
| Your help is greatly appreciated!
|
|
| Kewei
|
|