Hi,<div><br></div><div>Thank you very much. It was quite helpful. </div><div>What is the best way (in terms of accuracy) to incorporate all of these repetitions in to one input to bedpostx? Should I concatenate all of the repetition (e.g. a total of 69 directions+B0s 4D files) and append their corresponding bvals/bvecs into single bvals/bvecs, or do I need to average the data prior to the bedpostx?</div>
<div>As both of them should increase the SNR, in yet different levels .</div><div><br></div><div>Regards,</div><div>Arash</div><meta http-equiv="content-type" content="text/html; charset=utf-8"><div><br><div class="gmail_quote">
On Tue, May 3, 2011 at 3:09 AM, Stamatios Sotiropoulos <span dir="ltr">&lt;<a href="mailto:[log in to unmask]"><a href="/cgi-bin/wa-jisc.exe?LOGON=A3%3Dind1105%26L%3DFSL%26E%3Dquoted-printable%26P%3D336196%26B%3D--bcaec53f2c6d2830cc04a2617a7c%26T%3Dtext%252Fhtml%3B%2520charset%3DISO-8859-1%26pending%3D" target="_parent" >[log in to unmask]</a></a>&gt;</span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">






<div bgcolor="#ffffff">
<div><font size="2" face="Arial">Hi,</font></div>
<div><font size="2" face="Arial"></font> </div>
<div><font size="2" face="Arial">if you average the 3 repetitions, you will increase 
the SNR by a factor of square_root(3). This will increase the resolving power of 
the dataset. I would take a look at the last two figures of the following paper 
<a href="http://www.ncbi.nlm.nih.gov/pubmed/17070705" target="_blank">http://www.ncbi.nlm.nih.gov/pubmed/17070705</a> , 
they will give you an idea of how resolving crossing fibres is benefitted from 
increased SNR and increased number of directions.</font></div>
<div><font size="2" face="Arial"></font> </div>
<div><font size="2" face="Arial">Cheers,</font></div>
<div><font size="2" face="Arial">Stam</font></div>
<div><font size="2" face="Arial"></font> </div>
<blockquote style="border-left:#000000 2px solid;padding-left:5px;padding-right:0px;margin-left:5px;margin-right:0px" dir="ltr"><div class="im">
  <div style="font:10pt arial">----- Original Message ----- </div>
  <div style="font:10pt arial;background:#e4e4e4"><b>From:</b> 
  <a title="<a href="/cgi-bin/wa-jisc.exe?LOGON=A3%3Dind1105%26L%3DFSL%26E%3Dquoted-printable%26P%3D336196%26B%3D--bcaec53f2c6d2830cc04a2617a7c%26T%3Dtext%252Fhtml%3B%2520charset%3DISO-8859-1%26pending%3D" target="_parent" >[log in to unmask]</a>" href="mailto:[log in to unmask]" target="_blank">Arash 
  Nazeri</a> </div>
  <div style="font:10pt arial"><b>To:</b> <a title="<a href="/cgi-bin/wa-jisc.exe?LOGON=A3%3Dind1105%26L%3DFSL%26E%3Dquoted-printable%26P%3D336196%26B%3D--bcaec53f2c6d2830cc04a2617a7c%26T%3Dtext%252Fhtml%3B%2520charset%3DISO-8859-1%26pending%3D" target="_parent" >[log in to unmask]</a>" href="mailto:[log in to unmask]" target="_blank"><a href="/cgi-bin/wa-jisc.exe?LOGON=A3%3Dind1105%26L%3DFSL%26E%3Dquoted-printable%26P%3D336196%26B%3D--bcaec53f2c6d2830cc04a2617a7c%26T%3Dtext%252Fhtml%3B%2520charset%3DISO-8859-1%26pending%3D" target="_parent" >[log in to unmask]</a></a> </div>
  <div style="font:10pt arial"><b>Sent:</b> Monday, May 02, 2011 9:22 PM</div>
  <div style="font:10pt arial"><b>Subject:</b> [FSL] Minimum directions 
  required for FDT-PROBTRACKX</div>
  <div><br></div></div><div><div></div><div class="h5"><font face="tahoma, sans-serif">Dear FSL 
  experts,</font>
  <div><font face="tahoma, sans-serif"><br></font></div>
  <div><font face="tahoma, sans-serif">I&#39;ve read in FSL&#39;s 
  FDT FAQ that the least recommended directions necessary for 
  tractography is 25. Here I have a DTI dataset with 23 directions and 
  3 repetitions of the same sequence and directions.</font><span style="font-family:tahoma, sans-serif">I&#39;m planing to 
  run BEDPOSTX with default options (i.e. bedpostx -n 2). I was wondering if 
  having these 2 extra repetitions of the same 23-direction DTI would make 
  things look any better in PROBTRACKX.</span></div>
  <div><font face="tahoma, sans-serif"><br></font></div>
  <div><font face="tahoma, sans-serif">Thanks in 
  advance.</font></div>
  <div><br></div>
  <div>Regards,</div>
  <div>Arash</div></div></div></blockquote></div>
</blockquote></div><br></div>