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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