Uses of X Rays

Within a few weeks after Roentgen made his discovery, X rays were being used in medicine. Since then they also have had important uses in science and industry.

X rays help dentists detect diseases of the teeth. Doctors use X rays to locate bullets and other foreign objects within the body; to guide them in setting broken bones; and to detect cancer, ulcers, kidney stones, and other abnormalities.

Various types of X-ray scanners have been developed that allow highly detailed views of a particular section of the body. One type, known as a CT (computerized tomography) scanner, sends narrow beams of X rays at various angles through a patient's body. The information obtained from the X rays is processed by a computer to produce an image of a cross-section of the body. The image shows much more detail than an ordinary X-ray picture. A section of the body can be studied in three dimensions by producing a series of adjacent cross-sectional images.

X rays can halt the growth of cells and even destroy them altogether. They are therefore used to destroy benign and malignant tumors. X rays have also been used in the treatment of leukemia and bursitis.

X rays are used to inspect canned goods and other packaged products. A conveyor carries the goods past a beam of X rays. If a container is improperly filled, or if it contains a foreign substance, the X rays set off an alarm or set into action a device that removes the container from the conveyor. X rays are similarly used to separate beryl from granite and to inspect airplane and automobile parts, rubber goods, plastics, metal castings, and a variety of other products.

When used as a target in an X-ray tube, every element gives off X rays of specific wavelengths. These characteristic rays are used to analyze metal alloys, paint pigments, and other substances.

Scientists have learned much about the structure of matter by means of X rays. Among other things, they have learned how atoms are arranged in crystals. The average wavelength of X rays is about equal to the distance between the atoms in crystals. Crystals therefore act as diffraction gratings for X rays. That is, they scatter X rays in a pattern that shows the positions of their atoms.

When the patterns of specific crystalline substances are known, technicians can use X rays to analyze substances of which they are a part. Petroleum products, metal alloys, and other substances are thus analyzed.

Customs officers and airport security personnel use X rays in examining luggage and packages to check for weapons or smuggled articles. X rays show whether pearls are natural or cultured, and whether gemstones are natural or synthetic. X rays have also been used to learn whether paintings attributed to noted painters are authentic. Sometimes they have revealed changes made in the original work, or an earlier painting under the one that appears on the surface.