Open the drop-down menu of the Determine Group Layout icon 
in the Layout tab.
The display options include:
Single Dataset 2x2
Single Dataset 1x4
Multi Dataset 2x2
Multi Dataset 1x4
Multi Dataset no PET
All
Compare 1x3
Compare 2x3
Compare 3x3
Compare with NAC (No Attenuation Correction)
Tile
Compare with Prior 2x4
Compare with Prior 2x3
Compare with Two Priors
Compare with Three Priors
Compare with Four Priors
Compare with Prior no PET
Multiple Fuse
Multiple MIP
Common View 1x2
Common View 2x1
Common View 1x3
Select the display option you require.
NOTE: The list of layouts in the drop-down list, as well as the layout names, are configurable. See the system administrator to change the displayed layout names.
Saving layouts as key images
Click Mark Layout as Key 
in the Export toolbar to save the current layout as a key image.
See these topics:
Display Option: Multi Datasets
Display Option: Single Datasets