Help the development of the site, sharing the article with friends!
Thermal imaging cameras to detect temperature
The architecture and engineering sector has widely recognized the use of infrared thermography in different technical situations with well-trained professionals.
The infrared thermography It has been with us since approximately 1958, for construction, civil and industrial uses, experiencing great growth in the last 15 or 20 years. The thermal cameras they are more intuitive, ergonomic and offer increasingly better images providing more accurate analysis.
We were curious to recognize how thermal cameras can be used in the current pandemic caused by the coronavirus COVID-19 given the scarce information - in Castilian - that there is in the network.
An example with a thermal camera to measure temperature in action we find it in the following video …
Here, we have met Sergio Melgosa Revillas who is an expert and trainer in infrared thermography with his company EBuilding who has told us and clarified many concepts, doubts and procedures of how the thermal imaging camera can detect fever in people. So we started …
Relationship between COVID 19 and infrared thermography
The company Flir Systems, has been working and perfecting the fever detection systems with thermography (Fever screening) since 1999, with the first Asian epidemics (We assume that there are other companies, but in temperature chambers, at the level of Spain, it is well known).
Already in 2003 the first fixed fever detection stations were installed in airports in Asia, and today, Flir Systems guarantees an accuracy of 0.5 degrees in camera models suitable for Screening such as the ranges Exx, T series Y A320.
This means that there is enough experience and bibliography to generate confidence in this fever detection method, which, as we will see, brings many advantages.
Through infrared thermography we will be able to find people with a higher body temperature than the average of the people screened, which may be indicative of having a fever, and, in which case, those people would go on to a second, more in-depth review.
The generalized symptoms of the Coronavirus in broad strokes would be those indicated in the following image that we can also find more information and resolve doubts from the WHO here:
The common methods of temperature measurement in people that are being used in a generalized way there are three:
- The first, the contact thermometer.
- The second, a infrared thermometer which is usually placed in the ear (some also allow it on the forehead).
- The third method, the infrared thermography.
The Infrared thermography allows you to avoid having to touch the patient and also keep operators away from direct contact with the people being checked (Yes we will need a workplace with a stable temperature where the flow of the person to be checked can be controlled).
We remember that we wrote an article about a mobile with a thermal camera or how modern security cameras also use infrared at night.
Like every diagnostic technique and equipment, we find some limiting factors that we must be aware of, especially in this context …
Limitations in the use of infrared thermography
- By definition, the body temperature is the internal body temperature. This temperature We will NOT be able to measure it with a thermal camera since these equipments do not pass through human tissues. We can only measure surface temperature, logically at a lower temperature than the internal one.
- In addition, due to some technical aspects of infrared radiation and thermal imaging cameras, we will not be able to measure the absolute temperature of the surface either, although we do not have to.
- The technique that we will use will be based on detect a thermal abnormality in a person, from a group of people with a specific average temperature. We must therefore assume that most of the people we will review are healthy people and that the person with the highest temperature (1ºC for example) is the one who is likely to have a fever.
- We must also consider that there is much thermal variability between people, according to their metabolism, age or sex, so that we may not detect all cases possible fever rates of the test group.
Fever and infrared thermography
As we know, the beings humans we are isothermal (We all remember what they taught us in school: hot-blooded and cold-blooded beings, terms that are no longer in use), and this forces us to maintain an optimal operating temperature, regardless of the environmental conditions that surround us:
- If our central core overheats, exceeding 37 ºC, evaporative cooling (sweating) would begin.
- If the temperature drops below a certain level, body processes start to generate heat (shivering, for example).
We define normothermic temperature, as the temperature of a healthy person, and this varies between 36ºC and 37.8ºC. To have it a little clearer, in the following image it is detailed:
The rise in temperature is the body's response to disease or infection and is a typical medical indicator, along with blood pressure and pulse. So … How is it possible to measure the temperature at a distance and without direct contact with the object we measure?
The fever manifests itself among other things, with an elevation of the temperature in the head. This makes it easy to use infrared thermography Since, as we have said, we will not go through fabrics or materials (clothing). Although, the most precise areas before a temperature chamberThey are the cavities that we find in the head; the ear and the eyes.
The temperature elevation of the head due to fever facilitates the use of thermal cameras
The Thermal cameras do not measure temperature, they detect radiation intensities. It is related to temperature and enters into the physical laws that are studied and necessary to work in the field of thermography (For those interested in learning more, there are quality courses that can be consulted from HERE in Ebuilding)
In addition, there are factors that affect the amount of radiation that leaves the body (emissivity), that reflected by the body (reflectivity) and even the possible attenuation of the atmosphere that intervenes between the object and the camera. Fortunately, all these factors are practically irrelevant when we work with people, being the human body an excellent emitter of infrared radiation, and in general, we can use default values.
Methodology for the detection of Fever with thermal cameras
Remember that looking for people with a higher temperature than the rest, for the same situation. So the first thing to determine is what is meant by normal temperature.
We will assume that people will have a similar temperature, under the same conditions (room temperature, movement, etc.), as long as they do not have a fever. And we will also assume that most people do not have a fever. Thus, anyone who has a temperature significantly different from the rest is likely to have a fever.
How can we determine an average temperature to measure with thermal cameras? We can select the first 20 people to establish the average temperature of a healthy person, and based on this, establish the line from which we will establish the fever:
- The average temperature line will serve us for the rest of the days, although we can check our average temperature with other newly chosen samples.
- In the case of SARS, the WHO recommended detecting at least 1ºC above normal temperature. This can serve as an example for the case of COVID-19 if there is no other indication in this regard by any health authority. Below 1ºC we can run the risk of having numerous false positives.
- Both the mean temperature and the fever line should be recorded and checked at regular intervals. If we observe that we have numerous false positives (positives in the thermal camera that are later discarded by the health personnel), we will have to adjust the fever limit to 1.1 or 1.2 ºC instead of 1ºC.
If we establish a average temperature of the healthy person of 36.0ºC (remember that we are talking about the eye socket), a detected temperature of 37.0 ºC or higher would already be a case of possible fever and it should go to the assessment of the health personnel for a second review with an ear thermometer and already under the protocols of the health personnel.
The people in charge of detecting fever with thermography They will be in the first line of fire in the fight against the disease, and, therefore, their exposure to risk will be the highest (They must know the personal protection protocols - PPE used).
Now, we have to locate the best possible site for the fever screening station. This place must have:
- A reasonably stable temperature and be spacious. Queues will likely form to pass in front of the thermal camera.
- If several posts with a thermal camera are to be set up, this should be assessed, since a single post in a very tumultuous place (for example, airport) can be counterproductive and generate nervousness in the population.
- In the space or proximity, security personnel will be needed, to avoid bad behavior or refusals to the examination, and medical personnel to attend to people with fever following the corresponding protocols.
the scan should be done person to person, with the person being reviewed in front of the camera, for a period of 2 or 3 seconds
Today There are advanced software that allows you to configure alarms and detect fever in areas with greater crowds of people.. This should be assessed and the best possible solution chosen that allows faster reviews without compromising high reliability.
With respect to staff in charge of the fever detection station, we have:
- Cameraman- You will be responsible for the placement of the camera and its settings (focus, parameters, etc.). And who decides if that person passes the control or requires the review of medical personnel. Their concentration must be maximum since the task is very repetitive and long-lasting.
- Assistant: it will control the flow of people before passing in front of the camera, making sure that they are not wearing glasses, caps or any other element that prevents the correct capture of the image.
- Support person- It will direct people marked as positive (fever) towards the healthcare staff for evaluation, thus preventing the operator and assistant from interrupting their work and the queue of people from slowing down. In addition, you can attend to people's questions, take notes of interest, and so on.
Obviously, "the scan" with a chamber to measure temperature It can only detect infected people who are already showing symptoms of fever. Temperature scanning for possible cases can let in people who are incubating the disease, but it can certainly be a "first screen" that can help speed up a broader process of detecting the pandemic.
We remind you that we wrote an extensive article on types of mask; hygienic, surgical and PPE (FFP1, FFP2 and FFP3, and what are their characteristics and when should we use them.
If you liked this article, share it!
