Dear Bas,
a happy new year to you, too :) My limited experience with very
high-field, high-resolution images is that many operations on them
profit from removing the bias field which otherwise may interfere with
the determination of similarities and differences. You could therefore
play around with co-registering bias corrected versions of the
originals. With regard to the separation, I would rather include a third
step, as in [4 2 1] and see how much of a difference this makes in terms
of accuracy (and time!). I have never played with the other options as
far as I remember.
Hope this helps,
Marko
S.F.W. Neggers wrote:
> Dear List,
>
> first of all, best wishes for 2012 to the SPM community! Hope it will be
> a productive year for you all with lots of new and interesting
> developments.
>
> I was hoping for some advise. I am now working with high-field
> high-resolution images, and am trying to perform coregistration of 2
> images of different modality (EPI (DWI B0) to T1). The EPI data also has
> a near 1mm cubic resolution. It appeared to me that the default settings
> of coreg>estimate dont do a very good job for my data, results are
> always up to 2 mm off. Note that deformation of the EPI images is close
> to zero as we use very good real-time higher order shimming procedures
> during acquisition.
>
> Is it required to change some of the coreg options, for example
> 'separation', 'tolerance' or 'histogram smoothing'?
>
> I read in the manual that 'separation' refers to "The average distance
> between sampled points (in mm). Can be a vector to allow a coarse
> registration followed by increasingly fine ones.". The default is [4 2].
>
> When working with EPI and T1 data where EPI is also near 1 mm cubic,
> would for example [2 1] work better? It appears so, but I would like to
> hear about experiences others have with this. Also with respect of
> realignment and normalization of high resolution data.
>
> Thank you all in advance!
>
> Bas
>
>
--
____________________________________________________
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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