threetenfit - Fits three diffusion tensors to diffusion MRI measurements.
SYNOPSIS
threetenfit
<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 three
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 twenty-two 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, a_3, D_3xx, D_3xy, D_3xz, D_3yy, D_3yz, D_3zz]. 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 3 here; a_1 is the mixing parameter of D_1, a_2 that for D_2 and a_3 that
for D_3.
By default, the program constrains the three 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 three positive-definite diffusion-tensors to the data in SubjectA.Bfloat: