Hi,
Can you upload the 2 original input files that show this
behaviour to :
http://www.fmrib.ox.ac.uk/cgi-bin/upload.cgi
and let us know the 6-digit reference number?
Many Regards
Matthew
> Dear helpful people,
>
> I get negative radial diffusivity values, and I do not understand why.
>
> I am calculating radial diffusivity from the L2 and L3 images as
> follows:
> - I merge L2 and L3 for each subject: fslmerge -t dti_L23 dti_L2
> dti_L3
> - then I calculate their mean: fslmaths dti_L23 -Tmean Radial_D
> The resulting images, Radial_D contain lots of negative values, as
> if they
> are standardised across the image.
>
> Since the original L2 and L3 images only contain positive values, I
> don't
> understand how their mean can have negative values. I don't know
> exactly
> what fslmaths -Tmean does but until now I assumed it just calculated
> the
> mean of images over "time". Of course I could simply do fslmaths -
> add first
> and then fslmaths -div 2, but now I would like to know why my
> approach does
> not work.
>
> Best,
> Emma
>
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