twotenfit - Fits two diffusion tensors to diffusion MRI measurements.
SYNOPSIS
twotenfit
<data file> <scheme file> [-cylsym]
DESCRIPTION
Reads diffusion MRI data, acquired using the acquisition scheme detailed in the scheme
file, from the data file. The data file stores the diffusion MRI data in voxel order with
the measurements stored as big-endian four-byte floats and ordered as in the scheme file.
See modelfit(1) for the format of the data file and scheme file. The program fits a pair
of diffusion tensors to each voxel and outputs the results, in voxel order and as
big-endian eight-byte doubles, to the standard output. The program outputs seventeen
values in each voxel: [exitcode, ln(S(0)), m, a_1, D_1xx, D_1xy, D_1xz, D_1yy, D_1yz,
D_1zz, a_2, D_2xx, D_2xy, D_2xz, D_2yy, D_2yz, D_2zz]. An exit code of zero indicates no
problems. For a list of other exit codes, see modelfit(1). The entry S(0) is an estimate
of the signal at q=0; m is the number of fitted components, which is always 2 here; a_1
is the mixing parameter of D_1, a_2 is that for D_2.
By default, the program constrains the two diffusion tensors only to be positive
definite. The program can also constrain the diffusion tensors to have cylindrical
symmetry (two equal eigenvalues). This program is a simple interface to the program
modelfit. The modelfit program provides more options for fitting pairs of diffusion
tensors.
If the first command line argument is - the program reads data from the standard input.
EXAMPLES
Fit two positive-definite diffusion-tensors to the data in SubjectA.Bfloat: