Raheel,
I would think the easiest is to discard the volumes before you do
anything else (I do not even convert them). This will both use a more
representative volume for realignment and avoid the issue with the
non-matching number of volumes in the regressor later-on. The first
volume you keep will then be volume 1.
Cheers,
Marko
zafar raheel wrote:
> I need help regarding the above matter. In SPM during 1st level analysis
> we discard first few slides.
> 1. When we define onsets [e.g in time (seconds) not in scan], then we
> have to start from beginning e.g. from [0:4:500] or if I am discarding
> first 20 sec data then it will be from [21:4:500}. Which one is right?
>
> 2. In preprocessing, normally we do not discard the initial scans. But
> in DESIGN MATRIX, we are using realignment text file with the
> regressors. Now in realignment file we have information of all the scans
> but in first level analysis we have 10 scans (20 sec data) shorter than
> that.Will it will create problem or not?
>
> In other words, If I am discarding initial scans during first level
> analysis, whether I have to discard scans in preprocessing (realignment)
> as well or not.
>
> Secondly whether I have to start onset from 0 or from 21 [If I am
> discarding first 20 sec data, means 10 scans (as my TR is 2 sec)]
>
> Thanks
>
> Regards
>
> Raheel
--
____________________________________________________
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
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http://www.medizin.uni-tuebingen.de/kinder/epn/
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