And Follow Up
There are many recent news stories about “thermal scanners” being used to screen people at transit hubs, building entrances and other places where a person with an elevated temperature may be infected with the COVID-19 virus. It’s a straightforward idea that began during the SARS epidemic in the early 2000s and is well understood by many, but not all.
Seems to me it would be useful to summarize some of the factors used in selecting and using these devices for those who do not understand the important details. Also, I have listed some references below, not all free, but the Abstracts of most SPIE articles are free online.
Sales and marketing departments of the suppliers of these infrared temperature measuring devices may overlook, or not know the details themselves in their haste to make sales. So, be careful and thorough.
Sales and marketing departments of the suppliers of these infrared temperature measuring devices may overlook, or not know the details themselves in their haste to make sales. So, be careful and thorough.
Some of the keys to making effective use of thermal infrared imaging systems are:
- Insure that they are sufficiently sensitive and traceabley calibrated (making a measurement that is critical means the measuring devices must be calibrated and calibration without traceability is sub-standard, next to worthless, it provides the basis for measurement repeatability),
-
They are set up and aligned correctly (there are standards and reference examples available) and
- The staff using them is well-trained in both the use of the camera and the software that performs the analysis.
STANDARDS
IEC 80601-2-59:2017 “Medical electrical equipment - Part 2-59: Particular requirements for the basic safety and essential performance of screening thermographs for human febrile temperature screening”
https://www.astm.org/Standards/E1965.htm , “Standard Specification for Infrared Thermometers for Intermittent Determination of Patient Temperature” (Note that a thermal imager camera is basically an Infrared Thermometer “on steroids”, its technical name, if it claims to measure temperature, is a ‘2D Thermal Infrared Radiation Thermometer’).
https://www.fda.gov/medical-devices/general-hospital-devices-and-supplies/thermal-imaging-systems-infrared-thermographic-systems-thermal-imaging-cameras, “Thermal Imaging Systems” (Infrared Thermographic Systems / Thermal Imaging Cameras)
https://www.astm.org/Standards/E1965.htm , “Standard Specification for Infrared Thermometers for Intermittent Determination of Patient Temperature” (Note that a thermal imager camera is basically an Infrared Thermometer “on steroids”, its technical name, if it claims to measure temperature, is a ‘2D Thermal Infrared Radiation Thermometer’).
https://www.fda.gov/medical-devices/general-hospital-devices-and-supplies/thermal-imaging-systems-infrared-thermographic-systems-thermal-imaging-cameras, “Thermal Imaging Systems” (Infrared Thermographic Systems / Thermal Imaging Cameras)
https://www.iso.org/contents/data/standard/06/93/69347.html , “Medical electrical equipment — Deployment, implementation and operational guidelines for identifying febrile humans using a screening thermograph. (ISO/TR 13154:2017)”.
and,
Ghassemi, P., et al. (2018). "Best practices for standardized performance testing of infrared thermographs intended for fever screening." PLoS ONE 13(9): e0203302
and,
Ghassemi, P., et al. (2018). "Best practices for standardized performance testing of infrared thermographs intended for fever screening." PLoS ONE 13(9): e0203302
Screening in an efficient manner leads to then selecting those, hopefully few, who appear to have a fever and then to determine if they actually do. That means a second temperature measurement with either a contact or noncontact thermometer to measure more precisely.
Then those with true fevers can be further tested to determine their infection status; they might not have COVID-19, it could be another infection or they could have a higher than avarage, normal temperature.
I plan to follow this article with one on more accurate determination of a person’s temperature.
Some useful references:
“Enforcement Policy for Telethermographic Systems During the Coronavirus Disease 2019 (COVID-19) Public Health Emergency“, FDA’s Guidance for Industry and Food and Drug Administration - APRIL 2020The papers delivered in two sessions of ThermoSense XXVI (Proceedings of SPIE, Vol. 5405, “Medical Thermometry for SARS Detection I” and Medical Thermometry for SARS Detection II”; Papers 5405-06, 5405-07, 5405-08, 5405-11, 5405-12, 5405-13, 5405-14)
“Human radiation thermometry and screening for elevated body temperature in humans” Author(s): G. Raymond Peacock
“New blackbody standard for the evaluation and calibration of tympanic ear thermometers at the NPL, United Kingdom” Author(s): Helen C. McEvoy; Robert Simpson; Graham Machin
“Noninvasive temporal artery thermometry: physics, physiology, and clinical accuracy” Author(s): Francesco Pompei; Marybeth Pompei
”Development and deployment of infrared fever screening systems “Author(s): Yang How Tan; Chee Wah Teo; Eric Ong; Lay Beng Tan; Ming Jern Soo
Author(s): Li Wang; Sze Wey Chua; Victor Tan
”Infrared thermographic in identification of human elevated temperature with biostatistical and ROC analysis“ Author(s): Eddie Y. K. Ng; Gregory J. L. Kaw; Kelvin Ng
“Stop outbreak of SARS with infrared cameras “ Author(s): Yigang Michael Wu
G. Raymond Peacock "Temperature uncertainty of IR thermal imager calibration", Proc. SPIE 6205, Thermosense XXVIII, 620509 (18 April 2006); https://doi.org/10.1117/12.667848
”Comparison of 3 Infrared Thermal Detection Systems and Self-Report for Mass Fever Screening” Authors, An V. Nguyen, Nicole J. Cohen,
Harvey Lipman,1 Clive M. Brown, Noelle-Angelique Molinari, William L. Jackson, Hannah Kirking, Paige Szymanowski, Todd W. Wilson, Bisan A. Salhi, Rebecca R. Roberts, David W. Stryker, and Daniel B. Fishbein
Harvey Lipman,1 Clive M. Brown, Noelle-Angelique Molinari, William L. Jackson, Hannah Kirking, Paige Szymanowski, Todd W. Wilson, Bisan A. Salhi, Rebecca R. Roberts, David W. Stryker, and Daniel B. Fishbein
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