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annie.shepler
Starting Member

3 Posts
Posted - Sep 19 2008 :  3:49:26 PM  Show Profile  Reply with Quote
I need to generate the gradient sequence to process our DTI tensors; our DTI imaging protocol is below:

8 Channel SENSE
Parallel to AC/PC
128 x 128
15 directions
b-value: 800
TR: 17000
TE: 67.1
Voxel size: 2x2x2
Number of slices: 60
FOV: 25.6
Slice thickness: 2.0

Any help would be great!

petty
BIAC Staff

USA
453 Posts
Posted - Sep 19 2008 :  4:01:36 PM  Show Profile  Reply with Quote
if you acquired the scan here and you have a bxh header the directions are in that header.

1)X,Y,Z
2)X,Y,Z
3)X,Y,Z

<code>
<dimension type="diffusiondirection">
<size>56</size>
<datapoints>
<value>0 0 0</value>
<value>-0.387747134121 -0.296393661931 0.872813242996</value>
<value>-0.946163995722 -0.081321931027 0.313305660232</value>
<value>0.922518214794 -0.384882209717 0.028737223536</value>
<value>-0.444901340191 -0.161185017106 -0.880955270009</value>
<value>0.088648379736 -0.92988659956 0.357004729282</value>
<value>-0.398858764491 0.828672486485 0.392700389778</value>
etc, etc
</code>
Edited by - petty on Sep 19 2008 4:03:12 PM
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josh.bizzell
BIAC Staff

USA
118 Posts
Posted - Sep 19 2008 :  4:28:15 PM  Show Profile  Reply with Quote
Note: In my experience, the X & Y values in the BXH header need to have their sign flipped for the tensors to be correctly calculated with some programs. It might be worth testing with both.

Example:
<value>0.922518214794 -0.384882209717 0.028737223536</value>
would be
<value>-0.922518214794 0.384882209717 0.028737223536</value>

-Josh
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annie.shepler
Starting Member

3 Posts
Posted - Sep 22 2008 :  11:12:46 AM  Show Profile  Reply with Quote
Thanks!
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