-- KristiClark - 21 Feb 2008

tensor_indices

Purpose

Computes a variety of scalar indices from the eigenvectors & eigenvalues.

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Usage: ./tensor_indices input4D.img [optional outputs]
Note: Overwrite permission for the output is assumed.

-f FA.img Fractional anisotropy
-r RA.img Relative anisotropy
-m MD.img Mean diffusivity
-t1 tinv1.img First tensor invariant (sum of eigenvalues)
Note: this is also called the trace
-t2 tinv2.img Second tensor invariant
Tensor invariants described in Basser, 1997
-t3 tinv3.img Third tensor invariant (product of eigenvalues)
-j Joutput.img J metric (Bahn, 1999)
square root of 2nd tensor invariant divided by 3
-k Koutput.img K metric (Bahn, 1999)
2nd tensor invariant divided by 1st tensor invariatn
-gm geom.img Geometric mean of eigenvalues
-h harmonic.img Harmonic mean of eigenvalues
-vr VRoutput.img Volume ratio
-vf VFoutput.img Volume fraction
-cv CVoutput.img Coefficient of variation of the eigenvalues
-cl Clinear.img Describes how much the diffusion tensor is cigar-like
-cp Cplanar.img Describes how much the diffusion tensor is planar
-cs Cspherical.img Describes how much the diffusion tensor is spherical
-ca Canisotropy.img Ca=Cl+Cp=1-Cs (Westin et al., 1997)

More Detailed Information

Summary of equations: tensor_indices.doc