The "Photocopy" of Bones: X-ray

X-rays are a form of electromagnetic radiation, just like a visible light. In a health care setting, a machine sends individual x-ray particles, called photons. These particles pass through the body. A computer or special film is used to record the images that are created by the machine.

Structures that are dense, such as bones, will block most of the x-ray particles, and will appear white. Metal and contrast media, special dye used to highlight areas of the body, will also appear white. Structures containing air will be black and muscle, fat, and fluid will appear as shades of gray.

We now know that these rays are like light and radio waves, a form of electromagnetic radiation. X-rays have high energy and short wavelength and are able to pass through tissue. On their passage through the body, the denser tissues, such as the bones, will block more of the rays than will the less dense tissues, such as the lungs.

A special type of photographic film is used to record X-ray pictures. The X-rays are converted into light and the more energy that has reached the recording system, the darker that region of the film will be. This is why the bones on an X-ray image appear whiter as less energy passes through than the lungs, where more energy passes through.

In the early days of X-rays, images, such as that of Mrs. Rontgen’s hand, were produced differently: the bones appeared dark rather than white.

With the help of X-ray images, the doctors can correctly diagnose bone fractures. These images can also help them recommend the right treatment for the patients.