You can limit a tissue to a specified region or volume of interest (VOI). The boundaries of the volume define the area in which the tissue can be defined. Even if the highlight values include pixels outside the VOI, those pixels will not be considered when building the tissue.
1. From the 3D tab of the toolbar, click VOI 
.
2. Select a VOI shape (oval, square, or freehand).
3. Click once to draw the shape you want, then double-click to end drawing.
After you draw the VOI, it is applied through the entire volume.
4. Apply other tissue definition tools to define the desired tissue.
NOTE: The original VOI that you draw is called the base VOI and is marked in red. As you scroll through the rest of the volume, you will see interpolated VOIs that are marked in green.
Colors cannot be seen on black-and-white monitors.
See these topics: