Hi Anna,
Some other things to think about:
1) Are this scanners from different vendors?
2) Are you using headcoils with the same number of channels?
3) Are you able to match bandwidths and TE's across all scanners?
Each one of the above can cause a bias in your data. Mixing field
strengths for diffusion is, in general, not a great idea since there will
be differing SNR's at the same b-value.
regards,
Karl
> Hi, Anna!
>
> Generally, I say it's not a good idea. One way to keep things cleaner on
> the analysis end would be to have very well-balanced cohorts at each site.
> That is, you'd want to make sure that the same number of each group are
> equally represented at each site, so that the confound of scanner can be
> reduced - basically replicating the whole study at both places.
>
> Good luck!
> Paul
>
> On Wed, May 7, 2014 at 1:55 PM, Anna Greenwald <[log in to unmask]> wrote:
>
>> What do the experts think about the feasibility of acquiring diffusion
>> data at different sites (using different scanners and, possibly,
>> different
>> field strengths) and combining them into one analysis? Is this generally
>> a
>> bad idea because the scanners' different SNRs will make the data
>> incomparable? Or if it is possible, which acquisition parameters would
>> be
>> crucial to hold constant, and which are maybe not as critical? And what
>> could be done on the analysis end to keep things clean (I'm thinking of
>> things like including "scanner" as a separate factor in the analysis)?
>>
>> I'd love to hear your opinions!
>> Thanks, Anna
>>
>
--
Karl Helmer, PhD
Athinoula A Martinos Center
for Biomedical Imaging
Massachusetts General Hospital
149 - 13th St Room 2301
Charlestown, MA 02129
(p) 617.726.8636
(f) 617.726.7422
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