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Dear Peter, > we are facing a problem with the use of SPM99 on functional data sets > consisting of 6 contiguous slices. Our processing steps involve: > a) slice timing > b) realignment > c) coregistration > d) normalization (using the normalization parameters derived from the T1 > weighted high resolution anatomical data) > e) smoothing (8mm kernel) > f) statistics > > We find that in step c) the images appear to be slightly tilted towards > the back (in sagittal view). We now wonder, if (possibly due to the > limited number of slices) the coregistration can be skipped, or if this > step is necessary. > Anatomic and functional images were acquired with the same field of view > and orientation. > Further we wonder whether it would not be better to coregister the > functional scans to multislice, whole brain EPI images, (which we acquire > in the same session with the same FOV and slice thickness) to derive the > normalization parameters for the functional scans? I would skip the coregistration and normalise the small volume EPIs using the whole brain EPI images, as you have described it. It is possible to end up in a local minimum, when coregistering a limited number of slices. Especially rotation around the x-axis is a problem here. In the last step you can normalise your T1 high resolution image directly to the T1 template. This is possible because the T1 and EPI templates are in the same space. -Christian %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%