Hi everyone,<div><br></div><div>The DTI fit in MRtrix should handle multiple b-values fine. The CSD approach however cannot currently handle such data, as Thijs correctly stated. Luis, I'm surprised that you manage to get convincing results simply by stripping off the b=0 image, since it is ignored by csdeconv anyway (unless you use the -normalise option which is not recommended). In any case, it is definitely not designed to handle multiple b-values, so I would not advise planning your study around it...</div>
<div><br></div><div>Cheers,</div><div><br></div><div>Donald.</div><div><br></div><div><br><div class="gmail_quote">On 16 November 2012 07:41, Luis Concha <span dir="ltr"><<a href="mailto:lconcha@unam.mx" target="_blank">lconcha@unam.mx</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I have a similar data set to the one described by Romain (1x b=0, 32x b=1000 and 32x b=2000; the 32 gradient directions are identical for b1000 and b2000). <br>
<br>Perhaps I _shouldn't_ be doing it, but cdsdeconv seems to handle this data set perfectly when I strip off the b=0 image (my usual approach, as I am after CSF signal elimination). However, I just tested csdeconv with all three b values (0,1000 and 2000) and it seems to give similar results, up to an lmax=6 (I did not test any further).<br>
<br>The DTI maps look perfectly fine, with a slight increase in FA in regions partial voluming with CSF (fornix, callosum edges) in the non-b0 data set as compared to the b=0,1000,2000 data set.<br><br>Perhaps doing 2 shells is OK even in the absence of b=0, and the argument of multi-shell CSD invalidity is only applicable for >3 shells. Nonetheless, I would much appreciate it if you could direct me to the right papers in order to understand if I am doing things properly, as I plan to use this approach for a longitudinal 4-year study that is just about to begin.<br>
<br>Below is the gradient table used for the b=0,1000,2000 data set, and I am posting a snapshot of the orientation plots for the data sets I mentioned here:<br><a href="http://imgur.com/56Y8q" target="_blank">http://imgur.com/56Y8q</a><br>
<br><br>Thanks.<br><br><br clear="all">Dr. Luis Concha<br>Instituto de NeurobiologÃa<br>Laboratorio C-12<br>UNAM, Campus Juriquilla<br>
Boulervard Juriquilla 3001<br>Juriquilla, Querétaro.<br>C.P. 76230<br>México<br>Tel <a href="tel:%28442%29%202%2038%2010%2053" value="+524422381053" target="_blank">(442) 2 38 10 53</a><br>
Fax <a href="tel:%28442%29%202%2038%2010%2046" value="+524422381046" target="_blank">(442) 2 38 10 46</a><br><a href="http://www.inb.unam.mx" target="_blank">www.inb.unam.mx</a><br><br>
0.000000Â Â Â 0.000000Â Â Â 0.000000Â Â Â 0<br>-1.000000Â Â Â 0.000000Â Â Â 0.000000Â Â Â 1000<br>0.000000Â Â Â -1.000000Â Â Â 0.000000Â Â Â 1000<br>0.000000Â Â Â 0.000000Â Â Â 1.000000Â Â Â 1000<br>0.042400Â Â Â 0.114601Â Â Â -0.992506Â Â Â 1000<br>
-0.174909Â Â Â 0.200511Â Â Â -0.963951Â Â Â 1000<br>-0.232290Â Â Â 0.162593Â Â Â -0.958960Â Â Â 1000<br>-0.367520Â Â Â -0.026101Â Â Â -0.929649Â Â Â 1000<br>-0.190192Â Â Â -0.374383Â Â Â -0.907560Â Â Â 1000<br>0.116799Â Â Â -0.833394Â Â Â -0.540196Â Â Â 1000<br>
0.200489Â Â Â -0.252686Â Â Â -0.946548Â Â Â 1000<br>0.495782Â Â Â -0.134495Â Â Â -0.857969Â Â Â 1000<br>0.014100Â Â Â 0.628102Â Â Â -0.778003Â Â Â 1000<br>0.744490Â Â Â 0.147698Â Â Â -0.651091Â Â Â 1000<br>0.760877Â Â Â -0.320390Â Â Â -0.564283Â Â Â 1000<br>
0.180892Â Â Â -0.924660Â Â Â -0.335085Â Â Â 1000<br>0.679628Â Â Â 0.422417Â Â Â -0.599725Â Â Â 1000<br>-0.777100Â Â Â -0.470700Â Â Â -0.417800Â Â Â 1000<br>-0.924162Â Â Â 0.103596Â Â Â -0.367685Â Â Â 1000<br>-0.468485Â Â Â 0.767376Â Â Â -0.437786Â Â Â 1000<br>
-0.881688Â Â Â 0.189298Â Â Â -0.432194Â Â Â 1000<br>-0.690404Â Â Â -0.706204Â Â Â -0.156901Â Â Â 1000<br>-0.239096Â Â Â -0.757087Â Â Â -0.607990Â Â Â 1000<br>0.057800Â Â Â -0.983696Â Â Â 0.170299Â Â Â 1000<br>0.536773Â Â Â -0.836058Â Â Â -0.113494Â Â Â 1000<br>
0.991788Â Â Â 0.120698Â Â Â -0.042299Â Â Â 1000<br>0.996763Â Â Â -0.070897Â Â Â -<a href="tel:0.037899%C2%A0%C2%A0%C2%A0%201000" value="+3780549991000" target="_blank">0.037899Â Â Â 1000</a><br>0.872425Â Â Â -0.478114Â Â Â -0.101403Â Â Â 1000<br>
0.248714Â Â Â -0.933552Â Â Â 0.258114Â Â Â 1000<br>-0.118295Â Â Â -0.991861Â Â Â -0.047098Â Â Â 1000<br>
-0.337598Â Â Â -0.841495Â Â Â 0.421798Â Â Â 1000<br>-0.528585Â Â Â -0.840876Â Â Â 0.116297Â Â Â 1000<br>-0.996853Â Â Â -0.054997Â Â Â -0.057097Â Â Â 1000<br>-1.000000Â Â Â 0.000000Â Â Â 0.000000Â Â Â 2000<br>0.000000Â Â Â -1.000000Â Â Â 0.000000Â Â Â 2000<br>
0.000000Â Â Â 0.000000Â Â Â 1.000000Â Â Â 2000<br>0.042400Â Â Â 0.114601Â Â Â -0.992506Â Â Â 2000<br>-0.174909Â Â Â 0.200511Â Â Â -0.963951Â Â Â 2000<br>-0.232290Â Â Â 0.162593Â Â Â -0.958960Â Â Â 2000<br>-0.367520Â Â Â -0.026101Â Â Â -0.929649Â Â Â 2000<br>
-0.190192Â Â Â -0.374383Â Â Â -0.907560Â Â Â 2000<br>0.116799Â Â Â -0.833394Â Â Â -0.540196Â Â Â 2000<br>0.200489Â Â Â -0.252686Â Â Â -0.946548Â Â Â 2000<br>0.495782Â Â Â -0.134495Â Â Â -0.857969Â Â Â 2000<br>0.014100Â Â Â 0.628102Â Â Â -0.778003Â Â Â 2000<br>
0.744490Â Â Â 0.147698Â Â Â -0.651091Â Â Â 2000<br>0.760877Â Â Â -0.320390Â Â Â -0.564283Â Â Â 2000<br>0.180892Â Â Â -0.924660Â Â Â -0.335085Â Â Â 2000<br>0.679628Â Â Â 0.422417Â Â Â -0.599725Â Â Â 2000<br>-0.777100Â Â Â -0.470700Â Â Â -0.417800Â Â Â 2000<br>
-0.924162Â Â Â 0.103596Â Â Â -0.367685Â Â Â 2000<br>-0.468485Â Â Â 0.767376Â Â Â -0.437786Â Â Â 2000<br>-0.881688Â Â Â 0.189298Â Â Â -0.432194Â Â Â 2000<br>-0.690404Â Â Â -0.706204Â Â Â -0.156901Â Â Â 2000<br>-0.239096Â Â Â -0.757087Â Â Â -0.607990Â Â Â 2000<br>
0.057800Â Â Â -0.983696Â Â Â 0.170299Â Â Â 2000<br>0.536773Â Â Â -0.836058Â Â Â -0.113494Â Â Â 2000<br>0.991788Â Â Â 0.120698Â Â Â -0.042299Â Â Â 2000<br>0.996763Â Â Â -0.070897Â Â Â -<a href="tel:0.037899%C2%A0%C2%A0%C2%A0%202000" value="+3780549992000" target="_blank">0.037899Â Â Â 2000</a><br>
0.872425Â Â Â -0.478114Â Â Â -0.101403Â Â Â 2000<br>
0.248714Â Â Â -0.933552Â Â Â 0.258114Â Â Â 2000<br>-0.118295Â Â Â -0.991861Â Â Â -0.047098Â Â Â 2000<br>-0.337598Â Â Â -0.841495Â Â Â 0.421798Â Â Â 2000<br>-0.528585Â Â Â -0.840876Â Â Â 0.116297Â Â Â 2000<br>-0.996853Â Â Â -0.054997Â Â Â -0.057097Â Â Â 2000<br>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><font color="#ff6600" size="1"><b>Dr Jacques-Donald Tournier<br></b></font><div><font color="#ff6600" size="1">Research Fellow</font></div><div><font size="1"><br>
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