Cancer may be difficult to detect, but for some types of cancer, the earlier it is detected, the better are the chances of treating it effectively. Imaging techniques – methods of producing pictures of the body – have become an important element of early detection for many cancers. But imaging is not simply used for detection. Imaging is also important for determining the stage (telling how advanced the cancer is) and the precise locations of cancer to aid in directing surgery and other cancer treatments, or to check if a cancer has returned.