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dtshape

Section: User Commands (1)
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NAME

dtshape - Computes DT shape statistics.

SYNOPSIS

dtshape -inputfile <eig> -stat <statistic>

DESCRIPTION

Computes tensor shape statistics based on the eigenvalues l1 >= l2 >= l3. The full list of statistics is

  <cl> = (l1 - l2) / l1 , a measure of linearity,

  <cp> = (l2 - l3) / l1 , a measure of planarity,

  <cs> = l3 / l1 , a measure of isotropy.

Note that

cl + cp + cs = 1 .

<l1> = first eigenvalue

<l2> = second eigenvalue

<l3> = third eigenvalue

<tr> = l1 + l2 + l3

<md> = tr / 3

<rd> = (l2 + l3) / 2

<fa> = fractional anisotropy. (Basser et al, J Magn Reson B 1996)

<ra> = relative anisotropy (Basser et al, J Magn Reson B 1996)

  <2dfa> = 2D FA of the two minor eigenvalues l2 and l3
                sqrt(2 * [ (l2 - <l>)^2 + (l3 - <l>)^2 ] / (l2^2 + l3^2) )

                <l> = (l2 + l3) / 2

The input to the program is the output of dteig.

EXAMPLES

Compute the linear statistic for a data set

dteig < A.inv1.Bdouble | dtshape -stat cl -outputdatatype float > A.inv1.cl.Bfloat

Compute RA for a data set, output as NIFTI:

cat dt_eig_sys.Bdouble | dtshape -stat ra -header data.nii.gz -outputfile ra.nii.gz

Compute the planar statistic cp for a data set with two tensors in each voxel

dteig -inputmodel multitensor -maxcomponents 2 < A.inv31.Bdouble | dtshape -stat cp > A.inv31.cp.Bdouble

OPTIONS

-stat <stat>: The statistic to compute. See the list of statistics in the DESCRIPTION section.

AUTHORS

Philip Cook <camino@cs.ucl.ac.uk>

BUGS

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Time: 02:07:11 GMT, December 04, 2017

Dtshape