[Mrtrix-discussion] Is response=110 normal for white matter=400 in b0?

[Donald Tournier]

Hi Dorian,

That's a bit lower than I'd expect, I typically see about 3/4 of the b=0
intensity (I think). That's for a b-value of ~3000, I would expect it to be
lower than that for higher b-values. Basically, the first term in the
response function multiplied by ~0.28 should correspond to the mean DW
intensity averaged over all orientations. If that's not the case, I would
have a good look at your single-fibre mask (the mask from which you
estimate the response function), to make sure that all voxels included are
in sensible, single-fibre, pure WM locations. I also assume this is a
healthy volunteer? Otherwise T2 hyperintensity could explain this. If none
of this helps, maybe you can post an image of the response function, its
coefficients, and the b-value, SNR and number of directions of the data
set, just in case we can spot anything obvious from them...

Cheers,

Donald.





On 25 October 2013 16:21, Dorian P. <alb.net at gmail.com> wrote:

> Hi again MRtrix group,
>
> My processing works fine and I see the doughnut shape of the response
> function. On checking some quality parameters I noticed that my response
> function starts from ~110 while white matter values on b0 are around
> 350-450. Is this normal or should I look at anything to improve?
>
> This is not just a  case as I have  two HARDIs from the same subject, both
> around those values.
>
> Thank you.
>
> Dorian
> TJU
>
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>


-- 
*Dr J-Donald Tournier (PhD)*

*Senior Lecturer, **Biomedical Engineering*
*Division of Imaging Sciences & Biomedical Engineering
King's College London*
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