Radiographic testing is a general term that describes different techniques for taking images that allow doctors to visualize the body’s internal structures. Images produced by radiographic tests can be examined on computer monitors, printed or recorded electronically. Although many radiographic tests involve radiation, they’re considered safe because the dosages are very low. (However, they are generally not recommended for women who are pregnant or breastfeeding.)
X-ray beams (electromagnetic radiation) are used in many radiographic tests. Different parts of your body absorb X-rays differently. Your bones are the most absorbent, which is why they appear white on radiograph images. Less-absorbent fat and other soft tissues look gray. Air is the least absorbent, which is why lungs appear black.
Computed tomography (CT) scanning, also called computerized axial tomography or CAT scanning, is an imaging test that uses X-ray images and a computer to generate cross-sectional views, or slices, of your body. This test provides greater clarity and detail than traditional X-rays.
Magnetic resonance imaging (MRI) does not use X-rays. Instead, it uses strong magnetic fields and radio waves to produce cross-sectional images of organs and internal structures. MRI signals vary depending on the water content and magnetic properties of different parts of the body, allowing doctors see differences between tissues and substances.