[Mristudio-users] adjust gradients during initial AIR?

[susumu mori]

Hi Julie,

Strictly speaking, if you do coregistration and the registration includes
rotation, you get more accurate results by rewriting the gradient table
based on the rotation angle. If you click this button, it does this small
correction.
If your study is successful, you usually expect less than 1 degree of
rotation in average, while the test-retest reproducibility of typical 5-10
min DTI should be somewhere around 2-5 degree of fiber angle uncertainty. If
the subject moves like 5 degree, I would worry about the overall quality of
the image rather than check this box and become happy. So, I have a mixed
feeling about this button, but yes, it makes your paper more bulletproof. We
are working on reporting system, which warns you if there is excessive
subject motion or image degradation, but it is still work in progress.

The mean of b0 and DWIs (there is a dedicated button for that) should be
available independent of tensor calculation.

susumu

On Wed, Jan 6, 2010 at 3:40 PM, Julie McEntee <jmcentee at jhmi.edu> wrote:

>  Hi-
>
> There is an option at the bottom of the AIR window (in DTI-Studio) to
> “Adjust the gradients for the diffusion-weighted images.” When do/should you
> choose to do this?
>
> Also, when do tensor calculations, no longer outputs mean of B0’s
> (image.b0) and mean of DWI’s (image.iso). Am I missing something?
>
> Thanks for your help,
>
> Julie
>
> Julie E. McEntee, MA, CCRP
> Senior Research Program Coordinator
> Department of Psychiatry- Neuroimaging
> Johns Hopkins University School of Medicine
> 600 N. Wolfe St./Phipps 300
> Baltimore, MD 21287
> Phone: 410-502-0468
> Fax: 410-614-3676
>
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