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Andre, > I would like to replace the faulty images by the mean of the surrounding > images. For this I would use ImCalc in SPM12 with the following expression: > > ‘(i1+i2)/2’ Yes, although you could also use 'mean(X)' and activate "load images into matrix". Or you could use a combination of spm_select, spm_vol, spm_read_vols and spm_write_vol, but either way should work. > My question is: Is this newly created volume 3 “accepted” by SPM as the > third volume, e.g. when I specify first-level statistics? Or is > information in the header used for this? SPM will take the images as you supply them, assuming you know what you are doing. So if you select the images in a given order, they will be assumed to be in this order, temporally. > The header information is probably wrong in the newly created file, and > therefore it may mess up the assignment of files to timesteps SPM > internally (e.g. having file1 – timestep1; file 2 – timestep2; file3 > (newly created, wrong header) – ignored; file4 –timestep 3 = from now on > all onsets are wrong by one TR) If you supply one "new" image for each image missing, the information in the remaining "original" images should be correct. > If my solution doesn’t work, is there another easy and straightforward > way without the need to just leave out the image and adjust the onset > vectors? For instance, adjusting the header. I have not used it much but I think what you want can pretty easily be achieved by the ArtRepair toolbox. > (having an extra regressor for the bad volumes doesn’t work here because > they result in SPM error messages and abortion of the processing) This should not happen - if, in the ensuing analyses, you enter a null regressor for each volume you replaced, this should not lead to an error (unless you thus overspecify the model, with 60 regressors for 50 scans or so)?? Such a regressor would not, or should not, be different from any other regressor you enter, and should not lead to an error per se. Cheers Marko -- ____________________________________________________ PD Dr. med. Marko Wilke Facharzt für Kinder- und Jugendmedizin Leiter, Experimentelle Pädiatrische Neurobildgebung Universitäts-Kinderklinik Abt. III (Neuropädiatrie) Marko Wilke, MD, PhD Pediatrician Head, Experimental Pediatric Neuroimaging University Children's Hospital Dept. III (Pediatric Neurology) Hoppe-Seyler-Str. 1 D - 72076 Tübingen, Germany Tel. +49 7071 29-83416 Fax +49 7071 29-5473 [log in to unmask] http://www.medizin.uni-tuebingen.de/kinder/epn/ ____________________________________________________