Dear SPM experts,
we are two post-graduates students new to PET SPM analysis (we work usually on MRI data) and we are trying to do a clinical study on [18F]-FDG PET data based on the article "Rapid Assessment of Regional Cerebral Metabolic Abnormalities in Single Subjects with Quantitative and Nonquantitative [18F]FDG PET: A Clinical Validation of Statistical Parametric Mapping" by Signorini et al. (NeuroImage 9, 1999).
We realized a "home-made" PET template based on the average of 5 normal subjects (normalized on the SPM PET template) and later we normalized the estimated pathological subjects to this template in order to make a 2 sample t-test between all the normal subjects and each supposed pathological subject (again see the Signorini '99).
The problem is during the estimate step. We found the following message:
Running 'Factorial design specification'
Mapping files : ...done
Calculating globals : ...done
Design configuration : ...done
Saving SPM configuration : ...SPM.mat saved
Design reporting : ...done
Done
Done 'Factorial design specification'
Running 'Model estimation'
SPM8: spm_spm (v4515) 11:22:13 - 13/02/2014
========================================================================
Initialising parameters : ...done
Plane 91/91 , block 1/1 : ...done
Temporal non-sphericity (over voxels) : ...ReML estimation
ReML Iteration 1 : ...0.000000e+000 [+4.25]
SPM8: spm_spm (v4515) 11:22:14 - 13/02/2014
========================================================================
Initialising parameters : ...computingWarning: Matrix is singular to working precision.
> In spm_inv at 30
In spm_spm at 426
In spm_spm at 896
In spm_run_fmri_est at 33
In matlabbatch\private\cfg_run_cm at 29
In cfg_util>local_runcj at 1510
In cfg_util at 830
In cfg_ui>MenuFileRun_Callback at 1188
In gui_mainfcn at 96
In cfg_ui at 53
Failed 'Model estimation'
Error using ==> mtimes
Inner matrix dimensions must agree.
In file "C:\Program Files\MATLAB\spm8\spm_FcUtil.m" (v4137), function "sf_X1o" at line 742.
In file "C:\Program Files\MATLAB\spm8\spm_FcUtil.m" (v4137), function "spm_FcUtil" at line 301.
In file "C:\Program Files\MATLAB\spm8\spm_spm.m" (v4515), function "spm_spm" at line 458.
In file "C:\Program Files\MATLAB\spm8\spm_spm.m" (v4515), function "spm_spm" at line 896.
In file "C:\Program Files\MATLAB\spm8\config\spm_run_fmri_est.m" (v4403), function "spm_run_fmri_est" at line 33.
The following modules did not run:
Failed: Model estimation
We checked the data carefully for dimensional and orientation agreement between all the images and it was ok.
We also changed the numer of subjects in the control group and the problem didn't change.
Now we don't have any other ideas, so...
Any suggestion?
Thanks in advance,
Chiara and Francesca
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