Thermal Imaging or Thermography
Abstract
Thermography or Thermal Imaging refers to the Infrared imaging science which detects radiation of long
infrared radiation by the camera. The range of infrared electromagnetic spectrum varies between 9000 nm
to 14000 nm and the result image referred as Thermogram. It provides temperature distribution of skin
images in two-dimensional. In year 1960, it was developed or launched. Direct touch or contact with
body is not required in this. At present it is widely used in bio medical applications to produce image and
detect the disease. Since very early, temperature of body measurement estimates the time death of person
.Now a day’s its application is found in psychology, diagnosis, cancer, forensic medicine, skin disease,
plastic surgery, etc. Digital infrared thermal imaging (DITI) is highly used in clinical and research
purpose in pregnant woman too. In this review, we see the application, advantages and its successful use
in the bio medical field.
Introduction
From very past period of time, temperature measurement of body is natural indication of illness of body.
Thermography is a branch of science which deals with formation of image by infrared radiation by
thermal camera. Additional features like color can also be added to model [1]. At present, thermography
finds a wide application of use in industry and become important tool for industrial application for
problem detection and inspection. Its application is not limited to industry, but also in medical,
Smartphone, etc [1, 2]. In various applications the 3-D images of model is created with thermal image
techniques. The body skin temperature distribution decides the quality of infrared radiation and
temperature is decided by blood flow, metabolism, shell /core heat transfer, etc [2- 3-8]. It is estimated
that more than 101.2 millions of people in India with Diabetes by The International Diabetes Federation
[3]. In 1960, Thermography is introduced by U.S army for nighttime surveillance [4]. It can be used to
convert image data to scene temperature with high accuracy and requires high techniques and new
approaches [5]. Skin thermal value is also affected by body muscles contraction and can be used in
thermal imaging [6]. Most effectively used for detection of breast cancer, neurological conditions, etc [7].
Thermal cameras are capable of detecting temperature, diseases, injuries, stress, diagnosis process, etc. It
finds application in medicine or forensic medicine. The emissivity of target object infrared radiation
relative to black body is main parameter of camera [8-9-10-11-12-13]. Smartphone thermal cameras are
now also used as infrared sensors and working temperature ranges (0-100) degree, less resolution due to
compact nature [11]. In Covid 19, thermography plays important role and by computed tomography, we
easily measure temperature of body of patient and easily distinguish them [12].
Calibration of camera
Calibration is the important parameter of camera and consists of identifier/detectable markers at specified
location. After the identification of Calibration pattern, the image coordinates & spatial coordinates are
related through algorithm. The calibrated algorithm targets the object and its geometries [1].
Thermal Imaging in Medical sector
Thermal camera detects the temperature distribution of body skin via infrared radiation emitted that is
result of blood flow. It shows the heat transfer inner tissue, local tissue, metabolism, etc within body. This
technology provides functional information and is comparatively cheap method and risk free. This
thermography system when used to detect or treat any disease is free of physical activity restriction like
diet, exercise, etc. This camera easily detects radiation from body, without harmful radiation and on spot
report without waiting time [3]. In biomedical analysis, the blood is collected from human body and
obtains numerous parameter from these, that is HbA1c and the value of average glucose is measured in
mg/dl.
Figure 1 showing thermal image of body
Infrared thermography
Infrared thermography was first conducted or started by William Herschel’s in ‘‘dark light’’ in which a
portion of sun electromagnetic spectrum was invisible with naked eyes [4]. But with rise of temperature,
each produce different band of color of all visible light and observed dark light just after red light also
produce heat, which is first step towards infrared radiation. After that many experiments were done and
also thermal equations are applied like blackbody radiation, electromagnetic radiations, weins law,
kirchoff’s law, emmisivity, etc. the present modern devices are just like digital cameras and provide
temperature information of surface.
Figure 2 showing infrared thermography
Converting signal to temperature
Thermal imaging devices convert the electromagnetic radiation into temperature based image, known as
thermogram with the help of sensors. If we want to measure object temperature accurately, then it is only
possible with deep knowledge of radiative environment and physical environment of object. The present
modern technology uses many sources of Infrared energy for thermal image. The most common example
of this is
IRP = EPR + TRP + RRP
The above relation shows incident radiative power (IRP) is the sum of emitted radiant power (ERP),
transmitted radiant power (TRP) and reflected radiant power (RRP) [4]. The sensor measure mainly the
emitted radiative power (ERP) as it can easily converted to temperature of object surface by StefanBoltzmann & Planck’s law. The sensor senses the whole object surface temperature.
Covid 19 /corona virus
As Covid 19/corona virus is spreading among peoples and it transfers from people to people. In this
pandemic, WHO recommends to wear personal protective equipment (PPE) for health care [11]. Medical
masks, gloves, face shields, goggles, etc are included in PPEs.
Preventive measures for COVID-19 disease
In this pandemic prevention are the most effective tool and some of the prevention methods are




Touching of eyes, nose, face, and mouth must be avoided.
Minimum 1 meter of social distance must be maintained from persons.
Protection kits includes masks, gloves, etc must be wear regularly.
Proper hand wash with sanitizer, hygiene, etc must follow regularly.
This must be followed and additional precautions also necessary like self protection of health workers and
avoid transmitting. The health worker caring patients must wear PPEs properly, because it is the only
effective administrative package, environmental control as per WHO respiratory infection in health care.
Disruptions in the global supply chain of PPE
The PPE as per present scenario is not sufficient in whole world. But as the disease spreads rapidly the
masks, goggles, etc also become insufficient. To meet this global challenge many steps to be followed
such as

Minimize the need of PPEs



We can use telemedicine to check suspected cases, and thus reduce need of PPE.
Plastic window and glass can be used as physical barriers to reduce spread of covid 19.
Allow only direct contact health worker to enter patient room and other worker not allowed
ensuring minimum PPEs utilization.
 Ensure PPE use is rational and appropriate




PPE must be only used where risks and transmission environment only.
Health care worker must wear masks, gloves, eye protection, etc.
No medical mask is needed for non symptoms persons.
The person caring patients at home must avail medical masks.
 Coordinate PPE supply chain management mechanisms



PPE requests from countries must be monitored.
The duplication of stock must be avoided by having centralized control supply management.
The PPE distribution must be monitored from start to end.
 Diagnosing COVID-19
The patients were scanned using computed tomography (CT) and their lungs image is compared with well
healthy lungs. Thus the patients were easily detected or tested by thermography.
Conclusion
Thermography is the technique of producing images with the help of temperature distribution of body. It
is very useful as it detect disease or any interruption within the body without direct contacting it. It is also
quite important when touching/direct contact is avoided, such as in corona pandemic. Thermography
plays an important role to fight against Covid 19, as it easily detects temperature of body.
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