Model fit leading to viso 1, NDI zero and ODI 1 in all brain voxels #191
Description
Hi,
I have some noddi data acquired at bvalues of 700 and 2000. They were acquired in separate sequences one after another - they have been processed identically for distortion and eddy corrections and then merged together (so has the bvals and bvec).
The AMICO model does not produce any errors and results are saved. However, the fit_FWF is universally 1, fit_NDI is zero and fit_ODI is 1 in all brain voxels - they (FWF/ODI) basically look identical to the brain mask. Any ideas on why this is happening. Here is the screen output:
-> Precomputing rotation matrices:
[ DONE ]
-> Writing scheme file to [ 20180502_mr485_NODDI.scheme ]
-> Loading data:
* DWI signal
- dim = 141 x 141 x 80 x 106
- pixdim = 1.700 x 1.700 x 1.700
* Acquisition scheme
- 106 samples, 2 shells
- 12 @ b=0 , 30 @ b=700.0 , 64 @ b=2000.0
* Binary mask
- dim = 141 x 141 x 80
- pixdim = 1.700 x 1.700 x 1.700
- voxels = 348542
[ 7.6 seconds ]
-> Preprocessing:
* Normalizing to b0... [ min=-0.00, mean=0.08, max=2.22 ]
* Keeping all b0 volume(s)
[ 1.5 seconds ]
-> Creating LUT for "NODDI" model:
[ 11.2 seconds ]
-> Resampling LUT for subject ".":
[ 1.3 seconds ]
-> Estimating principal directions (OLS):
[ 00h 00m 01s ]
-> Fitting 'NODDI' model to 348542 voxels (using 16 threads):
[ 00h 00m 09s ]
-> Saving output to "AMICO/NODDI/*":
- configuration [OK]
- fit_dir.nii.gz [OK]
- fit_NDI.nii.gz [OK]
- fit_ODI.nii.gz [OK]
- fit_FWF.nii.gz [OK]
[ DONE ]