External Email - Use Caution Thanks for the input, all. Much appreciated.
On Thu, Jul 12, 2018 at 11:01 AM, Bruce Fischl <fis...@nmr.mgh.harvard.edu> wrote: > > from Tom.... > > ---------- Forwarded message ---------- > Date: Thu, 12 Jul 2018 16:51:31 +0100 > From: Thomas Nichols <thomas.nich...@bdi.ox.ac.uk> > To: Bruce Fischl <fis...@nmr.mgh.harvard.edu> > Cc: freesurfer@nmr.mgh.harvard.edu > Subject: Re: [Freesurfer] Cortical Thickness at Individual Vertices > > > External Email - Use Caution > > Hi Bruce! > James: I don't have any particular deep thoughts except, all things equal, > if you have a tenable > continuous summary of the mTBI deficits it will probably be more > sensitivity than a discrete > count-based summary of the deficits. > > Bruce's idea of comparing distributions is sound but probably will only > work well for mTBI effect > that are diffuse. For localised effects (that are not spatially > consistent), finding some summary > measure of the deficits are probably the best way forward. > > -Tom > > > On Thu, Jul 12, 2018 at 4:31 PM Bruce Fischl <fis...@nmr.mgh.harvard.edu> > wrote: > Hi James > > you could use techniques that compare the whole distribution of > thicknesses across subject populations. You could do a t-test or > something > non-parametric like a Kolmogorov-Smirnov or use permutation testing. > I'll > cc Tom Nichols so he can chime in with something more sophisticated > or > specific. > > cheers > Bruce > > > > On Wed, 11 Jul 2018, James Gullickson > wrote: > > > > > External Email - Use Caution > > > > All, > > I am comparing cortical thickness between subjects with and > without mild traumatic > brain injury > > (mTBI). So far the contrasts in QDEC have not been significant > after correcting for > multiple > > comparisons. I am not necessarily surprised at this due to the > heterogeneous nature of > mTBI in our > > sample, i.e. we do not expect any two subjects to have damage in > the same area. I am > interested in > > ways to compare cortical thickness that are not dependent on a > single ROI having an > effect across > > subjects. One way I have tried is calculating z-scores for the > values in the > aparc.stats file, and > > using the number of abnormally low ROIs as a dependant variable to > compare between > groups. > > > > Is there a way to look at thickness differences at an even more > general level? E.g. by > comparing the > > number of vertices with abnormally low thickness? If so how would > one go about that > with Freesurfer > > data? > > > > This paper takes a similar approach with DTI. I'd like to do > something analogous to > their "number of > > voxels with low FA" analysis. > > https://www.sciencedirect.com/science/article/pii/S105381191 > 1012146 > > > > Thanks, > > > > James > > > > > > > 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. > > > > -- > __________________________________________________________ > Thomas Nichols, PhD > Professor of Neuroimaging Statistics > Nuffield Department of Population Health | University of Oxford > Big Data Institute | Li Ka Shing Centre for Health Information and > Discovery > Old Road Campus | Headington | Oxford | OX3 7LF | United Kingdom > T: +44 1865 743590 | E: thomas.nich...@bdi.ox.ac.uk > W: http://nisox.org | http://www.bdi.ox.ac.uk > > _______________________________________________ > 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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