Streaks and dark bands

Streaks and Dark Bands.

In very heterogeneous cross sections, dark bands or streaks can appear between two dense objects in an image. They occur because the portion of the beam that passes through one of the objects at certain tube positions is hardened less than when it passes through both objects at other tube positions. This type of artifact can occur both in bony regions of the body and in scans where a contrast medium has been used. In the chest scan shown, the contrast medium has caused artifacts that might be mistaken for disease in nearby anatomy.