[Mristudio-users] Question regarding b-value

[susumu mori]

Hi Maya,

It is expected that diffusion constant like Eig is inverse proportional to
the b-value such that b x diffusion constant is a constant.
If you type in non-physical number like negative b, I believe (Hangyi
please correct me if I'm wrong) DtiStudio use b=1.
In your case, b x D = 1.1812.

If you use b=1 for all the past data, you can simply divide the number with
b=700. This is the case of all the numbers with the diffusion constant unit
(mm^2/s) like Eigs, mean diffusivity, trace, etc. I believe the unit-less
numbers such as FA is not affected.

Susumu

On Wed, Apr 18, 2012 at 3:11 AM, maya weinstein <weinmaya at gmail.com> wrote:

> Hi MRI studio users,
>
>
>
> In DTIStudio, in the "DTI Mapping" I noticed that the value I put in the
> "b-value" affects the results I get in the statistics.
>
> For example:
>
>  b-val 700: Eig 0= 1.69E-03
>
> b-val 70: Eig 0=0.0169
>
> b-val 7: Eig 0= 0.1687
>
>
>
> This seems to affect only the # of integers.
>
>
>
> But- when I use *b-val -7* (minus seven), I get an entirely different
> value:
>
> *Eig0= 1.1812*
>
> What does this mean? And is it a valid option?
>
> I used this option (b val= -7) and I want to know if I need to
> re-calculate the maps and reanalyze my data.
>
>
>
> Thank you,
>
> Maya
>
>
> --
> Maya Weinstein
> Department of Psychology, Bar-Ilan University
> Functional Brain Imaging Unit, Wohl Institute for Advanced Imaging,
> Tel-Aviv Sourasky Medical Center
>
>
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