Thanks for the quick responses. Figure 2 of that paper also answers my other question.
Best, Ariel On Mon, Aug 5, 2013 at 1:56 PM, Xu, Junqian <[email protected]> wrote: > Ariel, > > We recommend people to use these calculated b-values (including > cross-terms) instead of the input b-values. This was explained explicitly > at page 137, 2nd paragraph in > > http://www.ncbi.nlm.nih.gov/pubmed/23702418 > > "Small b value variations due to the cross-terms between diffusion and > imaging gradients are calculated (vendor supplied algorithm) in units of 5 > s/mm2 before the gradient nonlinearity correction" > > Regards > Gordon > > On Aug 5, 2013, at 4:46 PM, Ariel Rokem <[email protected]> > wrote: > > > Hello everyone, > > > > First of all, thanks for all the hard work on putting this data-set > together. I have been looking at some of the diffusion data and it's been a > good experience so far. > > > > I have a question concerning the encoding of b values in this data set. > Nominally, data was collected in 3 different shells (1000, 2000 and 3000 > s/mm^2), but the values encoded in the files are not exactly these three > values. That is, values are +/- 5-10 units from these three shells (and > from 0). As in:995, 990, 1005, 3005, 5, etc. > > > > Should we take these values literally? Was there a difference in the > diffusion encoding between these different directions? If so, why? > > > > Another related question: I recall a talk (at ISMRM?) in which one of > the researchers affiliated with HCP mentioned fluctuations of b value > across the volume (I apologize not remembering who this was...). Does > anyone have a good reference about these fluctuations, for this data, or > other data? > > > > Thanks again for your help with this question and for all the work on > this, > > > > Ariel Rokem > > Department of Psychology > > Stanford University > > _______________________________________________ > > HCP-Users mailing list > > [email protected] > > http://lists.humanconnectome.org/mailman/listinfo/hcp-users > > > > > _______________________________________________ > HCP-Users mailing list > [email protected] > http://lists.humanconnectome.org/mailman/listinfo/hcp-users > _______________________________________________ HCP-Users mailing list [email protected] http://lists.humanconnectome.org/mailman/listinfo/hcp-users
