fit_harmonics_grids_diff

Spherical harmonic fitting using paired linear/nonlinear transform differentials.

fit_harmonics_grids_diff <lin_xfm1> <nl_xfm1> <mask1> [...] [options]

DESCRIPTION

fit_harmonics_grids_diff fits spherical harmonic coefficients to distortion fields derived from the difference between paired linear and nonlinear transforms. For each input triplet, the tool computes the displacement between the linear and nonlinear transforms within the masked region, then fits spherical harmonics to the resulting differential field.

This approach is useful when distortion is estimated by comparing a linear (affine) registration with a nonlinear registration of the same data. The difference isolates the nonlinear distortion component, which is then modelled parametrically using spherical harmonics.

OPTIONS

--verbose

Print progress information during processing.

--clobber

Overwrite the output file if it already exists.

--order n

Maximum order of the spherical harmonic expansion.

--skip n

Skip every n-th voxel during fitting to reduce computation time.

--limit val

Exclude voxels with displacement magnitude above this threshold.

--par file

Initialize fitting from an existing parameter file.

-o, --output file

Write the fitted parameter file to the specified path.

EXAMPLES

# Fit harmonics from a single linear/nonlinear pair
fit_harmonics_grids_diff linear.xfm nonlinear.xfm mask.mnc \
    -o output.par --order 10

# Fit from multiple transform pairs
fit_harmonics_grids_diff lin1.xfm nl1.xfm mask1.mnc \
    lin2.xfm nl2.xfm mask2.mnc -o output.par --order 12

AUTHOR

Vladimir S. Fonov - McConnell Brain Imaging Centre, Montreal Neurological Institute.

COPYRIGHTS

Copyright © 2009-2024 by Vladimir S. Fonov

SEE ALSO

fit_harmonics_grids , fit_harmonics_grids_regularize