Luke,
I keep on mentioning that in cases of unexplained segmentation /
normalization failures, I suspect image inhomogeneities are to blame
unless proven otherwise. Take one of your failing subjects and write out
a bias corrected version in native space (ignore the tissue maps). If
you can then segment that bias-corrected version all right, bingo.
May the force be with you (sorry, couldn't resist :)
Marko
Luke Stoeckel wrote:
> Dear list,
>
> I posted some time ago about some segmentation errors we are observing
> while attempting to normalize our data. We are using SPM8 and have tried
> unified segmentation (with and without DARTEL...with and without New
> Segment) - segment MPRAGE and apply normalization parameters to EPI
> scans. We collected standard MPRAGE and EPI data on a Siemens Trio 3T
> scanner using a 32-channel head coil. The wacky segmentation results
> only occur for some participants (as observed in the segmented T1 images
> for GM and WM). These errors are happening more in our older
> participants who smoke, but we also observe errors in some otherwise
> healthy control participants with seemingly normal neuroanatomy. We have
> reoriented and co-registered the MPRAGE and EPI images and made sure
> these were in the same orientation as the templates, but still no luck.
> Has anyone else experienced similar errors? Any suggestions for
> additional steps to try?
>
> Thanks!
>
--
____________________________________________________
PD Dr. med. Marko Wilke
Facharzt für Kinder- und Jugendmedizin
Leiter, Experimentelle Pädiatrische Neurobildgebung
Universitäts-Kinderklinik
Abt. III (Neuropädiatrie)
Marko Wilke, MD, PhD
Pediatrician
Head, Experimental Pediatric Neuroimaging
University Children's Hospital
Dept. III (Pediatric Neurology)
Hoppe-Seyler-Str. 1
D - 72076 Tübingen, Germany
Tel. +49 7071 29-83416
Fax +49 7071 29-5473
[log in to unmask]
http://www.medizin.uni-tuebingen.de/kinder/epn/
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