[Mrtrix-discussion] Minumum scan requirements for CSD

[J-Donald Tournier]

Hi Helen,

We've been looking into this very issue here over the last year or so. We
have data acquired using a sequence that is essentially identical to what
you describe, and also using a 64 direction, b=2,500 sequence. The tracking
is improved using the higher b-value, but I'm not sure what the optimal
value actually is. In this population, it might very well be the case that
a slightly lower b-value would give enough information (the diffusion
signal is much smoother as a function of orientation in this age range than
it is in adults). For this reason, you can probably afford to lower the
b-value to some extent compared to adults, and you also don't need to
sample as densely over the sphere (i.e. you can use fewer directions). We
haven't got as far as really testing this out thoroughly, though. On the
other hand, Kerstin Pannek had an abstract on this issue (ISMRM 20: 3161;
2012), which suggested b=1,500 gave the best results. So my gut feeling is
b=1,500 or so, and as many directions as you feel comfortable with... As
long as you have at least ~30, angular sampling will be sufficient - any
further increase will essentially improve your overall SNR.

Hope this helps,
Donald.


On 4 December 2014 at 18:11, Helen Carlson <
Helen.Carlson at albertahealthservices.ca> wrote:

>  Hi there
>
> First, thank-you for all the previous help you have given our team through
> this list. It has been absolutely crucial!
>
>
>
> I am wondering about the minimum scan requirements for running CSD and
> getting realistic, useable results. Ideally we would have >60 directions
> and a high b-value but in reality we scan a paediatric population and so
> scan duration ends up being the most important variable in the equation.
>
>
>
> We currently use:
>
> -          32 directions
>
> -          3 b0
>
> -          B-value=750
>
> -          Voxel size 2.2 isotropic
>
> -          0 repetitions
>
>
>
> Is this sequence sufficient to run CSD and get meaningful results? We have
> successfully run the CSD and the tracts look great, I just need your expert
> opinions as to whether we are too far off with our parameters to really
> capitalize on the benefits of CSD?
>
> Thanks
>
> Helen
>
>
>
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-- 
*Dr J-Donald Tournier (PhD)*

*Senior Lecturer, **Biomedical Engineering*

*Division of Imaging Sciences & Biomedical EngineeringKing'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
<http://www.kcl.ac.uk/medicine/research/divisions/imaging/departments/biomedengineering>*
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