Each reference image contains a pair of default MPR cross-section lines (one vertical and one horizontal). You can move these lines individually to show different cross-sections in axial, sagittal, and coronal views. For example, if you move a default MPR cross-section line from side to side, the changing sagittal images appear.
When there are multiple images in one group, four additional cross-section lines appear on the reference images. The four cross-sections represent the following cross-section slices:
First
Currently active
Middle
Last
You can move or rotate a cross-section to a different angle to change the data shown in the result images. You can also change the cross-section slice thickness and spacing.
See these topics:
Changing the Slice Thickness and Spacing