The spread of Coronavirus (COVID-19) has encouraged people and organizations to take steps to reduce the spread of this highly infectious disease. Many are turning to thermal imaging as a non-contact method of rapidly screening for people with a fever, a symptom of infection. In this application, thermal imagers detect elevated body temperatures, which is an indicator of fever. If you are considering utilizing thermal imaging as a method of EBT monitoring*, it is essential to understand how thermal imaging works, best practices, and factors that can affect your measurements.
Thermal Image Elevated Body Temperature Monitoring
You will find the deployment of thermal imagers to monitor large areas and groups of people; this is not the recommended utilization. Thermal imagers calculate temperature by detecting infrared radiation emitted from the surface of anything in the field of view. The resolution of the imager indicates the number of point measurements. The more pixels on a target, the more accurate the temperature measurement. When a thermal imager looks at a crowd from a distance, your measurements are less reliable. This reduction in reliability is because, among other factors, there are few pixels on each target.
In the case of measuring EBT, we measure the temperature of a person's skin. More specifically, we want to measure the medial canthus of the eye. Research has shown this location to be the best for estimating internal body temperature using a thermal imager**. To achieve reliable results, you should follow some best practices. First is using a camera with sufficient resolution, the camera should have a resolution of about 320 x 240 or higher. This resolution ensures you have enough points measuring your target to get accurate temperatures. The person should stay about 1 meter away with their head filling most of the field of view looking into the camera. People must also remove their eyewear as the imager will be unable to see through glass. To learn more about the basics of thermography, you can refer to our post Thermography 101
Things to be aware of
Using this system as a means of early detection can be extremely useful, but there are some factors to be aware of that can impact your measurements. One thing that can affect your measurements is user error. To get accurate readings, you want to be sure that you measure the correct location on the face and that the person is standing still. It is also important to be attentive to outside factors that might change your measurement. If people are coming from outside where it is particularly cold, you will likely see temperature readings that are a few degrees colder. Also, be aware of if the person is sweaty or wearing make-up as these can also affect your temperature measurements.
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* Thermal imaging should not be used to diagnose coronavirus. Our solutions can identify individuals that show relatively higher than normal temperatures. There is no way to detect an infected individual who doesn’t have an elevated body temperature and only a medical professional can determine if an individual is experiencing an abnormal medical condition.
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Ghassemi, Pejman, et al. "Best practices for standardized performance testing of infrared thermographs intended for fever screening." PloS one 13.9 (2018).
Mercer, James B., and E. Francis J. Ring. "Fever screening and infrared thermal imaging: concerns and guidelines." Thermology International 19.3 (2009): 67-69.
Nguyen, An V., et al. "Comparison of 3 infrared thermal detection systems and self-report for mass fever screening." Emerging infectious diseases 16.11 (2010): 1710.