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

[Dorian P.]

The single fiber mask contains voxels out of brain, from skull etc. I will
make some attempts to better refine the DWI mask up in the processing
pipeline.

However, I still see good fiber tractography. What is the effect of low
response function on CSD results?

Yes, this is a healthy control.

You help is appreciated.
Thank you
Dorian


2013/10/28 Donald Tournier <jdtournier at gmail.com>

> 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
>>
>> _______________________________________________
>> Mrtrix-discussion mailing list
>> Mrtrix-discussion at www.nitrc.org
>> http://www.nitrc.org/mailman/listinfo/mrtrix-discussion
>>
>>
>
>
> --
> *Dr J-Donald Tournier (PhD)*
>
> *Senior Lecturer, **Biomedical Engineering*
> *Division of Imaging Sciences & Biomedical Engineering
> King's College London*
> *
> *
> *A: Department of Perinatal Imaging & Health, 1st Floor South Wing, St
> Thomas' Hospital, London. SE1 7EH
> *
> *T: +44 (0)20 7188 7118 ext 53613*
> *W:
> http://www.kcl.ac.uk/medicine/research/divisions/imaging/departments/biomedengineering
> *
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.nitrc.org/pipermail/mrtrix-discussion/attachments/20131028/d408a5cb/attachment-0001.html>