AFNI program: 3dnoise
Output of -help
Usage: 3dnoise [-blast] [-snr fac] [-nl x ] datasets ...
Estimates noise level in 3D datasets, and optionally
set voxels below the noise threshold to zero.
This only works on datasets that are stored as shorts,
and whose elements are all nonnegative.
-blast = Set values at or below the cutoff to zero.
In 3D+time datasets, a spatial location
is set to zero only if a majority of time
points fall below the cutoff; in that case
all the values at that location are zeroed.
-snr fac = Set cutoff to 'fac' times the estimated
noise level. Default fac = 2.5. What to
use for this depends strongly on your MRI
system -- I often use 5, but our true SNR
is about 100 for EPI.
-nl x = Set the noise level to 'x', skipping the
estimation procedure. Also sets fac=1.0.
You can use program 3dClipLevel to get an
estimate of a value for 'x'.
Author -- RW Cox
++ Compile date = May 31 2013
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Mon Jun 3 08:37:38 EDT 2013