Brain Innovation

Displaying VOIs with Volume Rendering

BrainVoyager's real-time volume rendering can display anatomical datasets and statistical maps (VMR and VMP files), but it currently lacks support for volumes of interest (VOIs). This article shows how you can use volume rendering for VOIs anyways, by first converting the VOIs to maps.

Display a single VOI

These instructions assume BrainVoyager is showing a VMR and there are one or more VOIs listed in the Volume-Of-Interest Analysis dialog.

1. In 3D Volume Tools (full dialog), go to the Segmentation tab. Under Reload, click the Non-Marked button, then the Marked button. This should clear the volume, leaving it completely black. Leave the Segmentation tab open; we'll need it again later.
2. In the Volume-Of-Interest Analysis dialog, select a VOI, click Options and go to the VOI Functions tab. Under VOI -> Draw in VMR, click Convert. This "draws" the VOI into the volume data, setting the corresponding voxels to intensity value 240.
3. Go back to the 3D Volume Tools (Segmentation tab) and click Options. In the Operations tab, click VMR -> VMP and then click OK to close the dialog.
4. Open the Volume Maps dialog (Analysis > Overlay Volume Maps). The VOI should now appear as a map called "VMR As Map". Click the map to enable it.
5. Below the list of maps, there's an input field labeled "Min:" where you can set a threshold for the map. Set the threshold to 240. In the Statistics tab, you can now select the color you would like next to "Color +Min:".

You can now save the map to a VMP file by clicking Save As in the Volume Maps dialog. Before you start volume rendering, click Reload All in the 3D Volume Tools dialog to get the VMR data back.

Display multiple VOIs

As above, this assumes you've opened a VMR and there are several VOIs listed in the Volume-Of-Interest Analysis dialog. Repeat these steps for each VOI that you'd like to display with volume rendering:

1. Follow steps 1 to 5 above to convert the VOI.
2. In the Volume Maps dialog, double-click the map's name to change it (otherwise they'll all be called "VMR As Map"). Use the Save As button to save the VMP to a file, then click Delete All and Close.

When you've converted all the relevant VOIs, click Reload All to reload the VMR. Open the Volume Maps dialog again and use the Add button to add each of the VMPs. Go to the Advanced tab and click Multiple Selections. Go back to the Browse tab and click each map to enable it.

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