Hello Martin,
Could you please find any time to answer me ?
Many thanks !
Best regards,
Matthieu Le 30 sept. 2015 13:57, "Matthieu Vanhoutte" matthieuvanhoutte@gmail.com a écrit :
Hi Martin,
Thank you for helping !
- What should I use for the parameter estimation: "mass univariate" or Novel
mass-univariate tools (spatiotemporal models)" ?
- I have one group of subjects with different timepoints (non equally
spaced and different numbers of timepoints), and would like to see the significant change of FA according to time. Will LME study allow me to get this change and how to define contrast to assess it ? Are the results of this longitudinal study directionals, i.e. is it possible to establish an increase or decrease of FA in significant regions according to time ?
Should the covariates (age, gender...) be demeaned or centered ?
Has the accurate time variable to be in years absolutely or could it
be also in days ?
Best regards,
Matthieu
2015-09-29 17:11 GMT+02:00 Martin Reuter mreuter@nmr.mgh.harvard.edu:
Hi Matthieu,
use lme_mass_fit_vw and the y is a simple vector. I would mask the image before doing this and only pass the brain voxels (to increase speed and reduce comparisons).
Best, Martin
On 09/29/2015 10:43 AM, Matthieu Vanhoutte wrote:
Hi Martin,
I understand for the multiple comparisons problem. But if I consider a voxel-by-voxel analysis just as hippocampal volume (lme_fit_FS for estimation), how could I consider a correction for multiple comparisons in this univariate case ?
Shouldn't I use the lme_mass_fit or lme_mass_fit_vw functions in my mass univariate case ? If yes, how do I have to format my 3D FA volume as input of the LME toolbox ?
Best regards,
Matthieu
Matthieu Vanhoutte, MSc Research Engineer - Department of Neuroradiology Regional University Hospital, Lille, France
2015-09-29 16:34 GMT+02:00 Martin Reuter mreuter@nmr.mgh.harvard.edu:
Hi Matthieu,
yes, multiple comparisons are a problem for any mass univariate approach. You can use the FDR2 correction (in the lme matlab tools) which is less conservative than standard FDR. You can also work in specific ROI's and average there, to reduce the number of comparisons.
Best, Martin
On 09/29/2015 09:11 AM, Matthieu Vanhoutte wrote:
Hi Martin,
Thank you for your answer.
However, I would like to consider FA maps as a mass-univariate problem and not a univariate voxel-by-voxel as hippocampal volume. Indeed, my voxels aren't independant, are they ? So, how to correct for multiple comparisons then ?
Best regards,
Matthieu
2015-09-29 15:04 GMT+02:00 Martin Reuter mreuter@nmr.mgh.harvard.edu:
Hi Matthieu,
if all your images are perfectly registered, you can do LME on a voxel-by-voxel basis, just as if you had hippocampal volume or any other ROI measure.
Best, Martin
On 09/29/2015 06:46 AM, Matthieu Vanhoutte wrote:
Dear experts,
I would like to know if it is possible to make a longitudinal study with LME toolbox from volume FA maps registered in a common space ?
I don't have T1 images so the recon-all process couldn't be processed. But if I put my 3D FA volume of dim = [nx,ny,nz] in a 1D nx*ny*nz voxels format, could it be in good way for LME ?
Thanks for helping !
Best regards,
Matthieu
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-- Martin Reuter, PhD Assistant Professor of Radiology, Harvard Medical School Assistant Professor of Neurology, Harvard Medical School A.A.Martinos Center for Biomedical Imaging Massachusetts General Hospital Research Affiliate, CSAIL, MIT Phone: +1-617-724-5652 Web : http://reuter.mit.edu
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-- Martin Reuter, PhD Assistant Professor of Radiology, Harvard Medical School Assistant Professor of Neurology, Harvard Medical School A.A.Martinos Center for Biomedical Imaging Massachusetts General Hospital Research Affiliate, CSAIL, MIT Phone: +1-617-724-5652 Web : http://reuter.mit.edu
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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 listFreesurfer@nmr.mgh.harvard.eduhttps://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
-- Martin Reuter, PhD Assistant Professor of Radiology, Harvard Medical School Assistant Professor of Neurology, Harvard Medical School A.A.Martinos Center for Biomedical Imaging Massachusetts General Hospital Research Affiliate, CSAIL, MIT Phone: +1-617-724-5652 Web : http://reuter.mit.edu
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.
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Matthieu Vanhoutte