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First move your
cursor on the image to a point where you have the best
view of your region of interest to select.
The click "Select VOI" on the main GUI.
You may select a region as large as you wish, within the memory and CPU
constraints of your computer. We typically select one hemisphere
and use a 5-8mm grid for quick initial analyses. Larger VOIs and smaller grid sizes
result in exponential increases in computing time and memory requirements. Whole head
VOIs with a fine grid may require more than 3-4GB of RAM and a lunch break.
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The axial view will be outlined
in red first, indicating the slice to select.
Click once at the edge of your desired VOI to start selection; trace your desired region, clicking to set anchor points.
Double-click or right-click to finish selection.
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The region you selected in the
axial section will now be highlighted in green, and the coronal slice
will now be bordered in red. Select the coronal section of
interest in the same way, and double-click or right-click when you are finished.
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The green area now indicates the
volume selected from both axial and coronal planes. The sagittal
slice is now bordered in red to indicate the final slice to select.
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Once you are finished, the final
volume will be highlighted in green. A file save box will
pop up, and you may optionally save your VOI to a ".mat" file for future use with other datasets.
It can be useful to do this if you want to process different MEG runs with the same VOI, or different
VOIs with the same subject. You may also hit "Cancel" to proceed without saving.
Either way, the VOI is also part of your NUTMEG "session"
and would be saved along with the rest of your data and computations when you "save session".
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