I don't quite understand what you are doing. Are these T1s from two different subjects? Do you have some form of ground truth with which to compare the estimated deformations? Best regards, -John On 3 May 2011 18:39, Pablo Ripolles <[log in to unmask]> wrote: > Hello SPMrs, > I am trying to compare deformation fields from 2 different T1s after being normalized with DARTEL and Unified Segmentation. After unified segmentation has run I get the deformation field from the .mat with the deformation utility. I do the same after Create Dartel has finished getting the def field from the flow field. Then I calculate the root mean square difference from voxels in the defformation field from image 1 and image 2 first for U.Segmentation and then for Dartel. What I want to see is which of the 2 algorithms performs better. > > > From recent results in papers I expect DARTEL to outperform unified segmentation (Klein et al, 2009) but this only happens when I take the mean rms of all the voxels in the deformation fields. When I calculate the mean root square difference for only the voxels from the defformation field which belong to brain, unified segmentation outperforms DARTEL. For def fields obtained from unified segmentation I use the brainmask provided with SPM8 to use only "brain voxels" and for def fields from DARTEL I use a mask obtained from the Template calculated by the algorithm . > > > As unified segmentation uses a small deformation approach and DARTEL a large deformation framework, are the results from de mean square roots comparable?Am I doing something wrong? > > I would really appreciate some help. > > Thanks to everyone in advance. >