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<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">Dear All,</SPAN><?xml:namespace
prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p></P>
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face="Times New Roman"> <o:p></o:p></FONT></FONT></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">I computed diffusion tensors and FA,
va0 (primary eigenvalue), va1 (secondary eigenvalue), and va2 (tertiary
eigenvalue) by linear fitting in DTIStudio. Then I save them into raw matrix and
read them in matlab.</SPAN><o:p></o:p></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><FONT size=3><FONT
face="Times New Roman"> <o:p></o:p></FONT></FONT></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">I found the number of non-zero (the
background is all zero) voxels for va1 and va2 is less than that of va0 or FA.
Such as:</SPAN><o:p></o:p></P>
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face="Times New Roman"> <o:p></o:p></FONT></FONT></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">number of non-zeros voxels for
va0 = 6311454<BR>number of non-zeros voxels for
va1 = 6310767<BR>number of non-zeros voxels for
va2 = 6248757<BR>number of non-zeros voxels for
va0 = 6311454</SPAN><o:p></o:p></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><FONT size=3><FONT
face="Times New Roman"> <o:p></o:p></FONT></FONT></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">This happens in all my datasets,
consistently.</SPAN><o:p></o:p></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><FONT size=3><FONT
face="Times New Roman"> <o:p></o:p></FONT></FONT></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">The voxels where va0~=0 & va1==0
are not a lot (a few hundred), and they mostly are at the edge of the brain, not
inside white mattter.</SPAN><o:p></o:p></P>
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face="Times New Roman"> <o:p></o:p></FONT></FONT></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">But the voxels where va0~=0 &
va2==0 are quite a lot (tens of thousand), and they resides mostly inside white
matter, such as corpus callosum.</SPAN><o:p></o:p></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><FONT size=3><FONT
face="Times New Roman"> <o:p></o:p></FONT></FONT></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">I would like to know why this
happens. </SPAN></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt"></SPAN> </P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">Moreover, when I try to, for
example, calculate the mean va2 within corpus callosum, how can I deal with
those voxels where va2==0 ? I think to treat them as equal to 0 sounds not
correct physiologically. But because there are a lot, I want to count those
points in, especially for small white matter structures (sometimes those va2==0
voxels can take up to 10% of a white matter structure). </SPAN></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt"></SPAN> </P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">Also, when I calculate radial
diffusivity (va1+va2)/2, the va2==0 points generate incorrect radial
diffusivity.</SPAN><o:p></o:p></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><FONT size=3><FONT
face="Times New Roman"> <o:p></o:p></FONT></FONT></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">Thank you very
much!</SPAN><o:p></o:p></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><FONT size=3><FONT
face="Times New Roman"> <o:p></o:p></FONT></FONT></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">Best,</SPAN><o:p></o:p></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">Yi</SPAN><o:p></o:p></P>
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face="Times New Roman"> <o:p></o:p></FONT></FONT></P></FONT></DIV></BODY></HTML>