Hi Bruce, What if she created an FSGD file, and instead of just having "patients" and "controls", she would have "patients1.5", "patients3", etc.? With over 400 subjects this should be feasible, i.e. the loss of d.f. is worth running the combined analysis.
Chris ________________________________________ From: freesurfer-boun...@nmr.mgh.harvard.edu [freesurfer-boun...@nmr.mgh.harvard.edu] on behalf of Bruce Fischl [fis...@nmr.mgh.harvard.edu] Sent: Monday, February 18, 2013 10:59 AM To: Jorge Jovicich Cc: Sinead Kelly; freesurfer@nmr.mgh.harvard.edu Subject: Re: [Freesurfer] Cortical thickness analysis on data acquired from multiple sites Hi Sinead I agree with Jorge - there is bound to be a substantial scanner effect. You might be better off keeping the data separate and treating the 3T as a confirmatory study. cheers Bruce On Mon, 18 Feb 2013, Jorge Jovicich wrote: > Dear Sinead, > > we found global significant differences in thickness between 1.5T and > 3T, in a group of subjects that was scanned at both scanners > (http://www.ncbi.nlm.nih.gov/pubmed/16651008). I think that nothing > stops you from doing the analysis, but maybe model in a field effect to > asset it in your own data. > > Cheers, > > jorge > > > On 18/02/2013 16:32, Sinead Kelly wrote: >> Dear members, >> >> I would like to get your opinion on this issue - I have a dataset of >> over 400 subjects but under half of this data was acquired on a 1.5T >> scanner and the rest was acquired on a 3T scanner. Would it be >> acceptable to conduct cortical thickness analysis on the combined >> dataset? From reading the literature it seems that this is not a major >> problem but I just wanted to get some more thoughts on this. >> >> Thank you for your help, >> >> Sinead >> >> -- >> Sinead Kelly >> Neuropsychiatric Genetics Group >> Trinity Centre >> St. James's Hospital >> Dublin 8 > > _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer The information in this e-mail is intended only for the person to whom it is addressed. If you believe this e-mail was sent to you in error and the e-mail contains patient information, please contact the Partners Compliance HelpLine at http://www.partners.org/complianceline . If the e-mail was sent to you in error but does not contain patient information, please contact the sender and properly dispose of the e-mail. _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
