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Some electromagnetic waves can be used in medicine for imaging purposes, which allows doctors to explore what is happening inside a person's body without having to perform surgery.

Infrared radiation

Infrared radiation is used in thermal imaging to produce a thermogram - an image of the body showing areas of different temperature. This helps doctors to diagnose patients, as parts of the human body may emit more infrared if they are hot due to infection or injury. A charged coupled device (CCD) absorbs infrared radiation to produce an image. Each pixel in the CCD detects the infrared radiation and the data can be processed using a computer.

X-rays

X-rays can kill cancer cells. Directing an X-ray beam onto skin cancer cells, or cancer cells inside the body, can help to cure cancer. X-rays can also be used to produce images of the internal structure of the body, helping doctors to determine whether bones are broken or fractured. This is because X-rays are absorbed by dense material such as bone, but pass through soft tissue. Once they have passed through the body, X-rays will darken a photographic film, allowing any fractured or broken bones to be identified.

A CCD can also detect X-rays. A computer can use the data collected by the CCD to make an image of a slice through a person's body. This is called computerised tomography (CT).

Gamma rays

Gamma rays are emitted from the nuclei of atoms. They have high energy and can kill cancer cells, as well as bacteria on food. They can also be used as a medical tracer. When gamma rays are used as medical tracers, a chemical containing the rays is injected into the body of a patient. An image is then formed when the gamma rays travel out of the body and are detected by a gamma camera.