Hi Graham, interesting. Does sound like it might be a bug. Could you send
an example image (tarred and compressed)? Either stick it on a web/ftp
site at your end or email it directly to me.
Thanks, Steve.
On Fri, 23 Apr 2004, Graham Wideman wrote:
> Folks:
>
> On inspection of bias output files, we sometimes see spurious values
> cropping up. For example, in a typical bias file, we see a range of numbers
> from say 1.75 to 2.25 or so. Then there will be just a few values at 2.5 or
> 3.2 or so.
>
> Per slice, there may be none of these odd values, or maybe 2 or 3 such
> pixels, generally located at the border between brain and non-brain (ie:
> bordering on the non-brain region that has zeros in the input volume, but
> still actually in the non-zero region.).
>
> Just on the basis of smoothness, it seems to me these values should not be
> occurring... any clues as to what's going on?
>
> When inspecting the actual output seg volume, we see that the input values
> have indeed been multiplied by these out-of-whack multipliers.
>
> We have several MRIs that exhibit this phenomenon.
>
> Using FSL 3.3 on linux.
>
> Thanks,
>
> Graham
>
Stephen M. Smith DPhil
Associate Director, FMRIB and Analysis Research Coordinator
Oxford University Centre for Functional MRI of the Brain
John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
|