Thank you all very much for your prompt responses!
I will stick to your advice and exclude the data.
Best regards
Julia
John Ashburner schrieb:
> I would suggest only realigning the data that you plan to use.
>
> I have copy/pasted some of the online help that may explain what you
> observed...
>
> Because of subject motion, different images are likely to have different
> patterns of zeros from where it was not possible to sample data. With masking
> enabled, the program searches through the whole time series looking for
> voxels which need to be sampled from outside the original images. Where this
> occurs, that voxel is set to zero for the whole set of images (unless the
> image format can represent NaN, in which case NaNs are used where possible).
>
> Best regards,
> -John
>
> On Friday 21 November 2008 14:12, Julia Weiler wrote:
>
>> Dear SPMers,
>>
>> I encountered a problem during preprocessing of my fMRI data using SPM5.
>> One of the subjects showed large movements (up to 4cm) during the last
>> quarter of the experiment. Due to that, the late scans did not cover the
>> whole
>> brain anymore (temporal lobe missing; see attached picture: the top panels
>> show an early scan on the left, a late scan on the right.)
>>
>> After realignment, the lower portion of the brain was missing in all
>> volumes,
>> whether acquired late or early during the experiments (see bottom panels
>> in the attached picture. left: early scan; right: late scan).
>> I tried both options "Register to first" and "Register to mean", but the
>> results
>> were the same.
>>
>> Due to the large movements, I may not be able to use the data of this
>> late experimental phase anyway. However, I would like to understand,
>> why the lower brain portion is missing in all volumes after realignment.
>> I would have expected that this is only the case in the late volumes, where
>> it was missing from the beginning on.
>>
>> Any advice would be aprreciated.
>>
>> Thanks
>>
>> Julia
>>
>>
>> Julia Weiler
>>
>> Ruhr-University Bochum
>> Inst. of Cognitive Neuroscience
>> Department of Neuropsychology
>> GAFO 05/606
>> Phone: +49-234-3223574
>> Fax: +49-234-3214622
>>
--
Julia Weiler
Ruhr-University Bochum
Inst. of Cognitive Neuroscience
Department of Neuropsychology
GAFO 05/606
Phone: +49-234-3223574
Fax: +49-234-3214622
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