X-rays are beams of energy. When they pass through the body, they cast shadows of internal structures. They pass through soft tissue, but are blocked by dense tissue such as bones and teeth. Photographic film records these shadows. Examiners sometimes inject substances that give contrast to soft tissues. These materials include barium, dyes, and radioactive mixtures.

X-rays are fairly safe, but excessive use can pose some health risks. The effects of radiation from repeated X-rays collects over a lifetime. Some effects depend more on the number of X-rays in the short term. Too much exposure can lead to serious illness. These include blood disorders, cataracts, skin problems, and cancer. However, healthcare providers are aware of these risks. They consider the person's total exposure before ordering X-ray tests.

Most people have had dental X-rays. These are extremely low dose tests that pose almost no risk. Chest X-rays are another common test. X-rays are often taken of broken bones. Mammography is a test recommended for early detection of breast cancer. These tests use extremely short bursts of X-ray beams and pose little risk.

Fluoroscopy produces a moving X-ray image of internal organs. A constant stream of X-rays passes through the person. This casts shadows of internal structures onto a fluorescent screen. Fluoroscopy reveals less detail than a standard still X-ray. It also exposes the person to somewhat more radiation. For these reasons, radiologists use fluoroscopy only when they need to see movement.

A CT scan produces an image of a cross section of the body. It uses X-ray beams, but provides much more detail than a standard X-ray film. CT is short for computerized tomography. Tomography means that the X-ray tube travels in an arc around the body. It sends many beams though the same flat plane. The beams are altered by the nature of tissues they pass through. These changes are detected on the other side of the body and analyzed by computer. The computer translates the image to a film that contrasts various tissue types in different shades. CT scans use less radiation than regular X-ray films. Therefore, they are relatively safe.

If you have questions or concerns about the safety of X-rays, ask your healthcare provider to explain the benefits and risks of procedures.

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