Hi Rosalia,If you have high enough a sample size, then yes, it is definitely preferable.As you say, it is also important to have the same protocol, not just the same machine, as clearly demonstrated in this study: A voxel-based morphometry comparison of the 3.0T ADNI-1 and ADNI-2 volumetric MRI protocols. http://www.ncbi.nlm.nih.gov/pubmed/25092796Cheers,Gwenaëlle------------------------------------------------------------------------------------------------------------------------
Gwenaëlle Douaud, PhD
Associate Professor & MRC Career Development Fellow
FMRIB Centre, University of Oxford
John Radcliffe Hospital, Headington
OX3 9DU Oxford UK
Switchboard: +44 (0) 1865 222 493
Fax: +44 (0) 1865 222 717
www.fmrib.ox.ac.uk/team/principal-investigators/gwenaelle-douaud
www.fmrib.ox.ac.uk/research/fmrib-interface-analysis-clinical-neuroscience-group
-----------------------------------------------------------------------------------------------------------------------
De : Rosalia Dacosta Aguayo <[log in to unmask]>
À : [log in to unmask]
Envoyé le : Lundi 22 février 2016 18h48
Objet : Re: [FSL] Intensity problems after running fslvbm_2_template..Need for helping.
Rosalia.Best wishes,Hi Gwenaëlle thank you a lot for the link.I think I will take a decision regarding using just one machine and discard the other ones. Just the same machine, model, and acquisition parameters...I think this is the best solution I can take for now, and the results will be valid then, as far as I know.2016-02-22 15:52 GMT+01:00 Gwenaëlle DOUAUD <[log in to unmask]>:Hi Rosalia,In general, we would advise against using FSL-VBM in a multi-centric analysis, but in any case, you should absolutely add the information of each centre in your GLM model (for more on these issues, see Multi-site voxel-based morphometry--not quite there yet: http://www.ncbi.nlm.nih.gov/pubmed/21324367).It is not surprising that you should see some differences in the GM maps coming from different scanners at different field strengths. In particular, subcortical GM is highly myelinated, and can appear, depending on the contrast-to-noise ratio, as GM or WM, or a mix of the two.Cheers,Gwenaëlle------------------------------------------------------------------------------------------------------------------------
Gwenaëlle Douaud, PhD
Associate Professor & MRC Career Development Fellow
FMRIB Centre, University of Oxford
John Radcliffe Hospital, Headington
OX3 9DU Oxford UK
Switchboard: +44 (0) 1865 222 493
Fax: +44 (0) 1865 222 717
www.fmrib.ox.ac.uk/team/principal-investigators/gwenaelle-douaud
www.fmrib.ox.ac.uk/research/fmrib-interface-analysis-clinical-neuroscience-group
-----------------------------------------------------------------------------------------------------------------------
De : Rosalia Dacosta Aguayo <[log in to unmask]>
À : [log in to unmask]
Envoyé le : Jeudi 18 février 2016 9h53
Objet : Re: [FSL] Intensity problems after running fslvbm_2_template..Need for helping.
RosaliaThank you,Could I sent you the some of the problems in a pdf file to your email directly?...if you need to see the first template generated I can attach you too.Hi Paul,I can not attach any screenshot because of the size.....:(2016-02-18 10:14 GMT+01:00 paul mccarthy <[log in to unmask]>:Hi Rosalia,Could you attach a screenshot which shows your problem?Cheers,PaulOn 17 February 2016 at 11:22, Rosalia Dacosta Aguayo <[log in to unmask]> wrote:RosaliaKind regards,Any help would be more than grateful,I have checked patient 123 (anterior email) and I have discarded it definitively because a big enlargment of the ventricles.... but what about regarding the other issue intensities?I see that subcortical structural grey matter structures are not all with the same "color" what means the following: caudate, for example, in some files appears with a grey color whereas in others appears in white color...and sometimes middle in white and middle in grey...this is worrying me a lot. As I am working with different kind of images, from different centers and different teslas (1.5 and 3)...I wonder if this will affect the final results.....Dear FSL experts,I am worried about one thing that I have noticed it is happening in my images: when I visually check every individual file that contains my 4D GM template before running fslvbm_3_proc.