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Manpage of shfit
shfit
Section: User Commands (1)
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NAME
shfit - Fits the spherical harmonic series to the log measurements.
SYNOPSIS
shfit
[options]
DESCRIPTION
Fits the spherical harmonic series to the apparent diffusion
coefficient profile. The program computes d = -1/b log(A(q)/A(0)) for
each measurements and fits the series to d as a function of q/|q|.
The output of the operation in each voxel is the array [exitCode, log
A^tar(0), c00, c20, Re(c21), Im(c21), Re(c22), Im(c22), c40,
Re(c41), Im(c41), ...], where ckl is the coefficient of the k-th order
spherical harmonic with index l; the exitCode indicates the success of
the operation and should be zero if everything worked OK; A^tar(0)
is the best fit MRI signal at b=0.
Fitting the spherical harmonic series is not particularly useful on
its own. More useful it to use the spherical harmonic series for
voxel classification, see voxelclassify(1). The anisotropy of the
spherical harmonic fit, which sfanis(1) can compute, is a useful
alternative to the fractional anisotropy, fa(1), which takes into
account departures from Gaussian displacements.
EXAMPLES
Fit the fourth-order spherical harmonic series to some synthetic data
with two dominant directions:
datasynth -testfunc 3 -voxels 1 -snr 16 -schemefile A.scheme | shfit -schemefile A.scheme -order 4 > test_SH.Bdouble
Compute the spherical harmonic anisotropy:
datasynth -testfunc 3 -voxels 1 -snr 16 -schemefile A.scheme | shfit -schemefile A.scheme -order 4 | sfanis -inputmodel sh -order 4 | double2txt
OPTIONS
Input/output data and simulations options are the same as modelfit(1).
- Options concerned with the spherical harmonic fitting:
-
- -order <Maximum series order>
-
Specifies the highest order of the series to fit.
SEE ALSO
modelfit(1), sfanis(1), sfplot(1), sfpeaks(1)
BUGS
AUTHOR
Danny Alexander <camino@cs.ucl.ac.uk>
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- EXAMPLES
-
- OPTIONS
-
- SEE ALSO
-
- BUGS
-
- AUTHOR
-
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