Non-contact infrared assessment of human body temperature: The journal Temperature toolbox

Figures & data

Table 1. Checklist to ensure correct use of NCIT for tracking human core temperature

	Purchasing any NCIT device	Tick if yes
1	The device has a stated accuracy of ± 0.3°C or lower	◽
2	The device has a minimum resolvable temperature difference (sensitivity) of 0.1°C. This is often stated as the “resolution” of spot infrared thermometers	◽
	Purchasing a thermal imaging camera
3	The total resolution of the raw image is at-least 320 × 240 image pixels	◽
4	The device makes drift compensation (self-corrections) to keep the camera within the specified accuracy	◽
	If no to above
5	An external temperature reference source (ETRS, black body calibrator) is used with the device. The ETRS will have a combined stability and drift error of 0.1°C or less over a 14-day period. The ETRS will have an expanded uncertainty below ± 0.3°C	◽
	Measurement location
6	Air temperature is stable, and between 18 and 24°C	◽
7	Air relative humidity is stable, and between 20 and 75%	◽
8	The room is free of forced air movement and sources of radiation (i.e., no reflective backgrounds, sunlight) that can impact the NCIT display temperature. A non-reflective cloth backdrop can be used to minimize sources of radiation.	◽
9	The room is at-least 2 × 3 meters in size	◽
	Device operation
10	The user has consulted the manual to determine the correct measuring location and distance from the subject.	◽
11	The device is not overdue a calibration (see manufacturer guidelines)	◽
12	The device emissivity is set to 0.98 for long wave IR cameras or devices	◽
13	The device has warmed up to room temperature for at least 30 minutes	◽
14	The device is taking a measurement from a 90° angle and perpendicular to the front of the subjects’ face	◽
15	For spot measurements, the target is specified as the center of the forehead	◽
16	For thermal imaging, the target is specified as the inner eye-canthus (i.e., inner corner of the eyelid)	◽
17	For thermal imaging, the rainbow color scale is used	◽
18	An absolute temperature threshold has been established through consultation with a healthcare professional or expert in the field of fever screening with NCIT	◽
19	Masks, eyeglasses, hats, and any other items obstructing the face have been removed	◽
	If using an ETRS
20	The ETRS in focus and large enough to be easily discriminated from the background	◽
21	The ETRS is no larger than 10% of the size of subject’s face (in a face only image)	◽
22	The ETRS is set to a temperature close to the threshold temperature (i.e., 35–38°C)	◽
	Reporting
23	Model/manufacturer of camera; accuracy, resolution, model of ETRS, lens type, software & emissivity used	◽
24	Location, environment (air temperature & humidity), Reflected temperature	◽
25	Any pre- ‘treatment of subjects scanned (i.e., acclimation to conditions)	◽

Figure 1. Two 10-year-old males, the top thermogram (a) shows a healthy (non-febrile) case. The bottom thermogram (b) shows a case of fever. Thermogram A shows a max temperature of 35°C at the inner eye-canthus. Thermogram B shows a max temperature of 38.6°C at the inner eye-canthus. Figure adapted with permission of QIRT Council [24]

Figure 2. Simulated data to show the relative temperature screening method. A rolling average (solid black line) of all data points is used as the reference temperature. A temperature threshold of 1°C above this rolling average (dashed line) would result in a positive temperature screen, as shown by the red circular symbols. All data points below this threshold (gray symbols) would screen negative

Ghassemi P, Joshua Pfefer T, Casamento JP, et al. Best practices for standardized performance testing of infrared thermographs intended for fever screening. Plos One. (2018).

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