These images show the various structures of the patients body in different shades of black and white, the reason for this contrast is because different tissues absorb different amounts of radiation. The tissues that absorb the most radiation will look white as is the case of bones, those who absorb a moderate amount of radiation will look gray, an example of this will be fatty or soft tissues, the lungs will usually look black because they are filled with air, and air absorbs very little radiation.