Dear Dianne:
You can get FA above 1 when you have negative eigenvalues.
Examples:
The numbers are listed in the ordered of eigenvalue 1,2,3, mean, and FA.
500 500 -500 167 1.16
500 400 700 533 0.28
500 -200 300 200 1.01
I typically ignore them. Others may have different opinions.
Hope this helps,
Hedok
Dianne Patterson wrote:
> Hello All,
>
> We have seen some values over 1 in our FA images...mostly these are
> around the edges, but sometimes they are in the brain.
> I know there was mention of this on the archives...and the suggestion
> was that it wasn't a problem...
>
> But I am concerned...how do we end up with these high values?
> Should they be thresholded out before further image processing?
>
> Is FSL unique in producing these high FA values?
>
> Any more information about the topic and/or suggestions about how to
> handle it would be appreciated.
>
> Thankyou,
>
> Dianne
>
>
>
> --
> Dianne Patterson, Ph.D.
> [log in to unmask] <mailto:[log in to unmask]>
> ERP Lab
> University of Arizona
> 621-3256 (Office)
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