Figure 4. Two-dimensional representation of a volume image from an anesthetized subject (#4) in which the surface of the lung is shown in shades of gray and areas of atelectasis are shown in white. Conceptually, this represents the view of a gray transparent three-dimensional model of lung shape, with a superimposed opaque white model of atelectasis. This anteroposterior view (top) clearly shows the right and left lungs, with a visible cardiac shadow. The lateral view (bottom) demonstrates that the atelectatic areas are located in the most dependent lung regions. In this view, down is posterior, and left is caudad.