[Mristudio-users] Scanner-specific gradients?

[Igor Yakushev]

Dear Susumu, dear Users,

I have a beginners question:
Should be the combination of gradients the same for all subjects imaged 
with the same scanner (i.e. scanner-specific gradients)? Or the 
gradients may be different for different scans/subjects (i.e. 
scan-specific gradients)? Such “individual” gradients (bvec) can be 
calculated using e.g. MRIcron.

For example, gradient table (as provided by radiologists) in the first 
case looks like:

0: 0, 0, 0
 1: -0.7, 0, -0.7
 2: 0.7, 0, -0.7
 3: 0, 0.7, -0.7
 4: 0, 0.7, 0.7
 5: -0.7, 0.7, 0
 6: 0.7, 0.7, 0

in the second case (calculated with MRIcron) completely different:

0: 0.000, 0.000, 0.000
 1: 0.704, -0.146, -0.695
 2: -0.710, -0.146, -0.689
 3: 0.004, 0.546, -0.838
 4: 0.003, 0.838, 0.546
 5: 0.706, 0.692, -0.149
 6: -0.708, 0.692, -0.142

Accordingly, results (tracks originated from the same ROI) are very 
different.

Thanks,
Igor