Thanks Doug and Bruce! 
this is the process I followed (just in case is of help for somebody else). Questions below.

One subject to fsaverage

mri_vol2vol --mov  $SUBJECTS_DIR/fsaverage/label/myROI.nii --o $SUBJECTS_DIR/fsaverage/label/myROI.mgh --reg from_mySubject_to_fsaverage.dat  --targ fsaverage/mri/T1.mgz


.mgh to .label

mri_cor2label --i $SUBJECTS_DIR/fsaverage/label/myROI.mgh --id 1 --l $SUBJECTS_DIR/fsaverage/label/myROI.label


.label in fsaverage to rest of subjects

mri_label2label --srcsubject  fsaverage --srclabel $SUBJECTS_DIR/fsaverage/label/myROI.label   --trgsubject S_01   --trglabel $SUBJECTS_DIR/S_01/label/myROI.label  --regmethod volume


.label to .mgh

mri_label2vol --label $SUBJECTS_DIR/S_01/label/myROI.label --o $SUBJECTS_DIR/S_01/label/myROI.mgh --identity --temp $SUBJECTS_DIR/S_01/mri/T1.mgz


statistics with mri_segstats and myROI.mgh



My question is: how can I save couple of steps?
1.- Can I use mri_vol2vol as mri_label2label, just specifying the source and target subjects without knowing the reg matrix? I couldn't make it work...

or at least:

2.- Is it possible to use .label with mri_segstats? I am not interested in the .label in any case but...


many thanks again for your help!
Gari





On Wednesday, July 3, 2013, Douglas Greve wrote:

Hi Gari, use --targ for a target volume (not a subject) to use as the template for the output. The target subject is actually stored in the register.dat file, so you can just spec --fstarg (no arguments)
doug




On 7/1/13 2:45 PM, Garikoitz Lerma-Usabiaga wrote:
Hi,
I want to obtain volume statistics from a ROI in fsaverage. 
I have register.dat and a .nii file (the ROI), but I don't now how to get to the .label.

The last try has been:
mri_vol2vol --mov $SUBJECTS_DIR/fsaverage/label/ROI.nii 
--o $SUBJECTS_DIR/fsaverage/label/ROI.mgh 
--reg $SUBJECTS_DIR/fsaverage/mri/transforms/my_own_register_created_with_bbregister.dat --targ fsaverage

(but it is failing, error:
corRead(): can't open file $SUBJECTS_DIR/fsaverage/COR-.info)

My next steps were:
cor2label (in fsaverage)
mri_label2label (per every subject)
mri_segstats (per every subject)


Is there any simpler method to accomplish the same? Or at least that it works?
many thanks,
Gari


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