Next, move the slider bar (or click the arrows next to it) to image 3/9. You're now looking at an illustrated key to help you understand what you'll be seeing in the CT images. Basically, the scanner creates a digital cross-sectional view of the human torso with the patient's back toward the bottom of the image.

But wait - if the person's back is at the bottom of the image, why do the lungs seem to be reversed? They aren't: In radiology, images are always displayed as if you're looking up from the patient's feet.

Now go to image 4/9, which is the upper slice from the lung of a patient named Anne. You can get a closer look with the Zoom In and Zoom Out buttons. While you're zoomed in, you can move around the image by clicking the Pan button. You can also change the image contrast by clicking the Contrast button, then adjusting the Minimum, Maximum, Brightness, and Contrast slider bars. (Click Reset to return to the original contrast.)