Use Clipping Planes to cut out parts of the image.
Open Clipping Planes by choosing View | Options from the 3DModel window menu and then choosing Clipping Planes near the bottom of the Options window.
You can cut off from the Top, Bottom, Left, and Right. Moving the slider farther to the left cuts out more of the image from each side.
If Enable Near/Far Clipping is toggled On, you can also manipulate these planes. The Near clipping plane can be particularly useful for seeing the relationship between objects in 3 dimensions.
Each slider ranges from showing the whole side to cutting to the middle of the model.