Are you trying to visualize the cross section of surface and slices?
In order to see the pial surface on the cross section of the volume, you can load:
1. Load brain image and pial surfaces in BrainSuite.
2. Move the green cross hair to where you want to see the cross section in the image.
3. Go to surface view and press x, y or z depending on which cross section you want to see. You can try these keys multiple times to toggle cross sections.
As mentioned earlier, there is no volumetric mask for the pial surface since it is at much higher resolution than the WM surface. Can you please let me know what you want to do so that we can figure out how to best do it within BrainSuite.