The portable WG520 Flu / Ebola Fever Screening Detection System identifies persons who may be suffering from Ebola, common influenza, SARS and other flu variants such as Avian flu, Bird and Swine flu etc.
- Airports and border checkpoints;
- Any large gatherings / conferences / meetings in public places;
- Government buildings;
- Health security screening at events and temporary locations;
- Military bases;
- Points of entry / Points of exit.
- Sea ports and ferry & cruise terminals.
DITI (Digital Infrared Thermal Imaging) is used for mass screening in the containment of pandemic disease by detecting a febril (fever) state in individuals.
The design for DITI to be affective for fever screening is dependent on a good understanding of the physiology and physics related to the specific pathologies that we are trying to screen for and is not restricted to temperature measurements alone.
Additionally, the technology must be simple and easy to install and operate.
The radiometric thermal data processed during real-time imaging must include calibrated reference sources, thermal pattern recognition and comparative analysis between individual people being screened.
A screening test should have high 'sensitivity' rather than 'specificity' and to be effective the false negative rate must be very low.
To achieve this false positive rate will be higher by necessity and so a 'secondary' level of screening should be implemented to bring the false positive rate to within a manageable level by the higher 'specificity' secondary level of screening.
The ongoing future of IR screening as part of containment strategies for pandemic outbreaks will continue to benefit and evolve from what we can now learn from this current Ebola outbreak.
Why use fever screening?
The justification for using thermal imaging in the containment of Ebola is based on a proactive and preventative strategy.
Thermal imaging as a fever screening tool is used as a first level mass screening test that is sensitive and accurate at identifying all individuals that are above normal temperature and have a systemic fever.
The initial level screening, primary screening provides little or no inconvenience or interruption of movement for the majority of people being screened.
At point of entry screening in airport environments our statistical experience has been that 2.2% (22 people in every 1,000) will generate a positive alert.
Of the 2.2% positives, secondary screening will show that 82% of these are 'false positives' for a febril state (systemic fever) and the remaining 18% (4 people) will have a systemic fever.
In almost all cases the positive subjects are diagnosed with non pandemic diseases and infections but the important fact is that any symptomatic (and in most diseases) infectious people are identified.
The 'false positives' (individuals who are cleared at the secondary screening) are made up of local inflammatory conditions such as dental infection, sinusitis, dermatitis, hormonal dysfunction (such as hot-flush) and simple artefacts such as drinking hot drinks or recent sunburn.
The benefits of covering points of entry with thermal fever screening are:-
- Deterrent to individuals considering travelling with un-diagnosed symptoms of fever;
- Flexibility in escalation of screening protocols due to level of risk;
- Reassurance for other travellers that could be exposed.
- High mortality;
- Highly contagious;
- Variable Incubation period;
- Virulent strain.
- Bodily fluids transmitted;
- Climate sensitive;
- Infectious state accompanied by substantial fever;
- Not carried or transmitted via interspecies.
Paired units can be operated by a single technician covering a wide field of view as above. Single units can cover multiple entry points if a 'choke' point is set up.
Primary Point of Entry Fever Screening Stations
Any positive travellers identified at a fever screen station (triggering the threshold alarm) will be re-screened with a higher level of specificity and either passed as a false positive (non febril) or confirmed as positive for having a systemic fever and then escorted to a designated holding area or first aid station for clinical evaluation.
Fever screening stations are self-contained and portable, so they can be set-up in temporary locations very quickly.
Single units can operate as primary mass screening stations as well as secondary screening stations. With multiple stations deployed, for high volume traffic, a single unit is normally designated as the secondary screening station.
Normal body temperature is dependent on:-
Age, Recent activity, The Individual, Time of day.
It is generally accepted that normal body temperature ranges between 36.1°C to 37.2°C (97°F to 99°F).
Choosing the Right System
Industrial cameras have a wide range of temperature measurement and as a consequence the sensitivity and accuracy is also spread over a wide range.
A medical camera like the WG520 system has a very narrow range of detection, within the range of human physiology and so our sensitivity and accuracy is concentrated in this narrow range of IR emissivity and temperature.
This provides higher sensitivity and easier protocols which are not as affected by the outside environmental factors as an industrial camera will be; because of the wide range detected in all industrial applications, emissivity from electrical equipment, lighting, reflective surfaces, sunlight, and other IR sources in the immediate area will affect the results and require the operator to be very skilled as a thermography technician.
This system is designed and built specifically for clinical use and the detection of physiological IR.
Industrial cameras have many features and functions that are irrelevant to medical applications and actually work against the sensitivity and objectivity of results.
Many of these features like edge enhancement, auto averaging and emissivity correction have to be disabled before the camera can be used for applications like fever screening.
Many industrial cameras without internal temperature reference calibration require an additional external black body calibration unit (at extra cost).
All industrial cameras have a 'lens correction' built in, this is because they use actual lenses (just like normal cameras) to focus and zoom. (in industrial applications they have to look at objects at all distances from very close to very far away) the industrial camera lens will absorb about 17% of the emitted radiation (IR) so this needs to be corrected for by the software.
The WG520 camera does not use standard camera lens, so there is no loss of signal from the object emitting the radiation. It uses a small germanium window which does not absorb measurable amounts of the emitted radiation, so we are detecting close to 100% of the IR being emitted from the human body. (no lens correction = better accuracy).
Industrial cameras all have a % of thermal drift, which they use software 'averaging' to compensate for. This does not make much difference to most industrial applications but it is very important when using thermography for clinical applications.
The only way to counter the problems of thermal drift is to have a reference temperature; industrial cameras do not have a stable reference temperature point.
All industrial cameras being used in airports for fever screening should have an outside temperature reference source (black body emitter or calibration emitter) that is seen within each view. (Basically an accurate temperature that can be seen by the camera and used to calibrate each frame.)
The WG520 uses proprietary technology which gives us an internal reference temperature accurate to 1/100th °C. This handles any thermal drift and calibrates the results on a frame by frame basis End result: more stable results, repeatability, better accuracy and less need to continually alter the range and scale of detection like the industrial cameras which give higher percentages of false positive and false negative results and demand a higher level of training to be operated efficiently.
The WG520 software has developed from over 20 years of medical research and is specific to the application of mass screening for physiological abnormality.
Industrial camera software has been adapted (at best) for fever screening from the industrial application software which is in most instances not suitable or easy to use by untrained operators. The actual definition is not as important as how accurate and sensitive those temperature measurements are, the higher the definition, the better the picture will look but this does not mean that the accuracy is any better.
What Field of View (FOV) is best?
The focal length of industrial cameras is generally short and using optical lens (25 degrees is common) to zoom in for distance reduces the accuracy by simply making the pixels bigger and reducing the field of view.
For fever screening we recommend the WG520 using an 11 degree field of view which make the temperature measurements more accurate at distance. We do not use an optical or digital zoom lens.
We can supply the WG520 with optional field of view, 11 degree, 17 degree, 25 degree, 32, degree. 50 degree and are happy to advise on the best options for specific requirements.
The focal ability of the WG520 with an 11 degree FOV is 1 meter (39 inches) to infinity.
The optimum focal length for fever screening is 7.3 meters (24 foot).
The focal length to stay within specification for fever screening is 6 foot to 35 foot, accurate measurements can still be made up to 70 feet but the area of the face will be so small that sensitivity will be low due to the number of pixels, 'individual temperature measurements' on the face.
- Alarm threshold can be adjusted manually or automatically optimised 11° field of view giving accuracy from 18 m down to 2 m, Allows for rapid movement of multiple people though a large area. Additional FOV available. 17°. 25°. 32°. 50°;
- Easy to use software with auto ambient correction and Auto averaging of individual persons gives better accuracy with less false positives and false negatives while proprietary threshold fever alarm (audio and visual) reduces the operator training time to one hour;
- Optimised frame rate of 7.5 fps giving temperature sensitivity of 0.01°c and increased accuracy, Additional frame rates available: 30 frames per second, 60 frames per second (special quote);
- Real-time screening means no need for queues;
- Simple user interface allows anyone to quickly become proficient at operating the system;
- Stable calibration over ambient temperature changes ensures excellent measurement repeatability;
- The software controls and buttons can be shown in any language;
- User can configure software as desired through a password protected graphical interface;
- Visible and audible alarms permit fast identification of alarm sources.
- Camera is compact and rugged;
- Camera operates at real-time update rates, and displays images in colour on a flat panel display;
- Can be set up and working within 3 minutes;
- Designed to operate 24/7;
- Displays thermal images and will give an alarm when a temperature exceeds the chosen threshold;
- Easy to use allowing non-technical users to operate.
- System is totally portable;
- System monitors individual persons temperatures;
- Temperature alarm threshold can be set to automatic mode or manual mode to accommodate the operator's preference;
- Temperature resolution is <0.25°C;
- Weatherproof option is available.
|Temperature range:||10º C to 50º C (50ºF to 122ºF)|
(after 1 minute warm-up)
|<0.3º C drift over the temp. range 18ºC to 30º C|
(< 0.5º F drift over the temp. range 64ºF to 86ºF)
|Focal Plane Array:||Amorphous Silicon micro bolometer|
|Pixels:||160 x 120; Interpolated to 320 x 240|
|Spectral Response:||7-14 microns|
|Thermal Sensitivity:||0.1º C @ 30º C (0.2º F @ 86º F)|
|Display colour:||Select from 5 colour- maps provided, or create a custom colour-map.|
|ISO band display:||Automatically set to selected threshold temperature.|
|Power Source:||95-225 VAC, 45-65 Hz|
|Battery/external DC option:||6-32 VDC, minimum of 3 Watts continuous, 1 Ampere for a short time at start-up.|
|Operating Temperature:||0º C to 60º C (32º F to 140º F)|
|Storage Temperature:||-40º C to 80º C (-40º F to 176º F)|
|Overall Dimensions:||12cm x 19cm x 14cm (4.7" x 7.5" x 5.5"), (HxWxD)|
|Weight of Camera:||1.7kg (3.7 lbs)|
|Weight of Camera Stand:||11kg (24 lbs)|
|Recommended Interval:||0º C to 60º C (32º F to 140º F)|
| || |
|Focal Length:||25mm (1")|
|Fields of View:||17º H x 12º V|
|Focus Range:||1m to infinity (39" to infinity)|
|Computer:||Desktop or mini tower PC.|
|Display:||15" flat panel touch-screen LCD.|
|Software:||Full featured with threshold detection, data logging, camera control.|
|Camera stand:||Roll-about stand included.|