Good point, I mean that the MRI observations have Rician-distributed
noise. My question however remains, is this considered in SPM or is it
assumed that the noise is Gaussian?
/Anders
2010-10-31 10:19, Gael Varoquaux skrev:
> On Sat, Oct 30, 2010 at 07:45:07PM +0200, Anders Eklund wrote:
>
>> An interesting discussion, do you know if SPM uses the fact that the
>> noise in MRI is Rician distributed and not Gaussian distributed?
>>
> Forgive me for asking a naive question, but is the noise in fMRI really
> Rician-distributed? The MRI-observation noise is Rician-distributed. I
> believe that this comes directly from the measurement process. However,
> with EPI, there are much more processes contributing to 'noise' than
> imaging noise, such as residual movement or vascular and respiratory
> noise.
>
> I am not even sure that the EPI-specific noise (such as
> field-inhomogeneity fluctuations that can clearly be seen in the
> ventricles) are Rician-distributed. If someone on the mailing-list who
> understands the physics behind the EPI noise could enlight me, I'd be
> much obliged.
>
> Gael
>
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Anders Eklund
Phd student
Medical Informatics, Department of Biomedical Engineering
CMIV, Center for Medical Image Science and Visualization
Tel: +46 73 6003790 mail: [log in to unmask]
Fax: +46 13 101902 web: http://www.wanderineconsulting.com/
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