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Thermal Imaging

hermographic image a woman’s head and neck

Thermographic image a woman’s head and neck (metamorworks, iStockphoto)

hermographic image a woman’s head and neck

Thermographic image a woman’s head and neck (metamorworks, iStockphoto)

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Learn about uses of thermal imaging as a medical imaging technology.

Thermal Imaging

There are parts of the electromagnetic spectrum that the human eye can’t see. This includes thermal infrared radiation. This is radiation with long wavelengths. Everything emits thermal radiation - even humans. Objects such as a stove element on high, emit radiation in the visible spectrum when it glows ‘red’ hot. Humans are not as hot as stove elements. We emit radiation in the infrared part of the spectrum. The intensity and distribution of wavelengths changes with temperature. If we can record the energy emitted by the thermal radiation, we can use it to look for temperature differences across an area.

The design of a thermal camera is similar to a regular camera. You need lenses to collect and focus the energy as well as a detector. Infrared wavelengths do not transmit through regular camera lenses. Lenses must be made from special materials such as the chemical element germanium. Specialized detectors such as microbolometers or cooled detectors are also needed. A thermal camera displays an image called a heat map. On heat maps, cooler temperatures appear purple and blue and warmer temperatures appear orange and yellow. The image below shows a regular camera image (top) and a thermal camera image (bottom). Notice that emitted radiation passes through the black plastic bag, but not through the eyeglasses.

Visible image (left) and thermal image (right)
Visible image (left) and thermal image (right) (Source: Public domain images by NASA/JPL-Caltech).

There are a number of Industrial uses of thermal imaging. Thermal imaging can show where heat is escaping around windows and doors. Thermal imaging can also help firefighters to see through smoke to find victims. In the scientific field, thermal imaging can help researchers to observe chemical processes.

Thermal imaging is non-invasive. This means that nothing breaks the skin or enters the body. This makes it very safe and painless. Scientists are now beginning to explore thermal imaging for medical applications. For example, thermal cameras are used in airports in countries like China and Mexico. They help to detect people who have high fevers. in places such as airports. This monitors and prevents the spread of diseases. Researchers in Montreal are also developing a way to use thermal imaging to help evaluate the severity of a burn.

Thermal image of arm with burn
Arm with a burn. The bright spot is the burn.The dark spot around the burn is cold from an ice pack on the arm (Source: ©2014 Catherine Greenhalgh. Used with permission).

Other current research explores how thermal images of the hands and wrists may reveal carpal tunnel syndrome. While hot spots on a thermal image of the neck could indicate a thyroid condition. 

Thermography provides a way to look at the heat distribution of an object. It has many industrial and medical applications. Thermography is not used as much as other medical imaging techniques currently. However, it may become more popular as scientists understand more about human heat mapping and ways it could be used to diagnose illnesses.



Science In A Minute: What is Infrared Light? (2020)

This video by NASA is a very brief overview of infrared light and its uses.

Infrared Astronomy

This NASA web page explains the importance of infrared light to the biggest questions in astronomy, and the telescopes used to detect it. Videos take you on tours of several nebula, showing the difference between visible light and infrared light.


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