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The program is part of the spherical-function PICo calibration routine. To calibrate PICo for diffusion tensors, see dtlutgen(1).
picocalibdata outputs a single voxel of synthetic data from a range of test functions. The single-fibre test functions are zero mean Gaussian (see datasynth(1)): G(.; D_1, tau), where tau is the diffusion time specified in the scheme file, and the tensor is
D_1 = diag((T-l_1)/2, (T-l_1)/2, l_1) .
By default, the program generates data from a range of test functions, where first eigenvalue l_1 varies such that the fractional anisotropy of D_1 ranges between 0.1 and 0.9. The trace of the tensor is T = 21 * 10^{-10} m^2 s^{-1} by default.
A different random rotation is applied to each D_1, so the test function is oriented randomly in each voxel.
The two-fibre test functions are
(1-a)*G(.; D_1, tau) + (a)*G(.; D_2, tau) ,
where 0.5 < a <= 1. The tensor D_2 is
D_2 = R^T * diag((T-m_1)/2, m_1, (T-m_1)/2) * R ,
where R is a rotation matrix, which specifies a rotation by an angle theta about the second eigenvector of D_1, so that the angle between the principal directions of D_1 and D_2 is (pi / 2 - theta).
By default, picocalibdata creates data from the two-fibre test function with many combinations of D_1 and D_2, such that the fractional anisotropy of D_1 and D_2 vary between 0.3 and 0.9, the angle theta varies between 0 and pi / 4, and the mixing parameter a varies between 0.5 and 0.8. A random rotation is applied to each test function before the data is generated.
The program outputs a text file containing information about the test functions used to generate the data. By default, this file is pico_calibration_info.txt.
Use the default parameters to generate data for a given scheme file, with an SNR of 20 in white matter in the unweighted image
picocalibdata -snr 20 -schemefile A.scheme > calib_data
Increase the range of single-fibre test functions and output text file to another location
picocalibdata -snr 20 -schemefile A.scheme -onedtfarange 0.1 0.9 -infooutputfile A_pico_calib.txt > calib_data
TP
-twodtfarange <min max> Fractional anisotropy range of two-tensor test functions. Default is 0.3 0.9.