Nav: Home

Cool eyes on fever screening: Optimizing infrared thermography

September 14, 2020

Thermography has been a hot topic this year, due to the need for quicker diagnostics to detect and prevent the spread of COVID-19. Noncontact infrared thermometers (NCITs) are currently a primary tool for fever screening, but their widespread use has been prone to inaccuracy. A related medical technology, thermography using infrared thermographs (IRTs), enables increased options for temperature estimation with greater accuracy. Although the use of thermography as a stand-alone detection method for COVID-19 is unlikely to prevent spread, emerging evidence and international consensus suggest that it is indeed possible to use IRTs effectively for detecting elevated body temperatures.

Journal of Biomedical Optics provides robust insights for optimizing IRT-based fever screening. The research, performed by Quanzeng Wang and collaborators at the Center for Devices and Radiological Health of the US Food and Drug Administration (FDA), evaluated the use of IRTs under standardized conditions. They examined clinical data for more than 500 demographically diverse individuals, including 47 subjects with elevated oral temperatures (>37.5 °C), correlating facial temperatures to oral under-the-tongue thermometer measurements. The team confirmed the utility of internationally recognized (ISO) standards for obtaining consistently accurate results, and specifically reported the efficacy of ISO methods, including facial area targets.

How do IRTs work?

We radiate heat as infrared energy, which changes as we get warmer. IRTs are camera systems that can sense infrared energy, allowing us to "see" the infrared waves. These readings display as a two-dimensional temperature distribution that correlates to temperature levels at the source. A human face typically shows varying temperatures, warmer where the larger arteries are closer to the surface of the skin such as the inner canthi (the eye corners where the tear ducts reside) and temples.

Optimizing IRTs

Like any technology, IRTs are subject to fundamental device and performance variations, which affect overall accuracy when used in medical practice. To minimize such variations, FDA researchers incorporated the ISO guidelines in their experiments (e.g., controlling ambient conditions, requiring individuals to acclimatize for 15 minutes prior to screening, etc.). They reported excellent IRT performance with clear correlations between IRT readings and oral temperature baseline data.

Aside from demonstrating the effectiveness of standardized methods for fever screening, some key insights emerged from the team's analysis.

One of the most significant insights was that targeting the full face for temperature screening resulted in greater accuracy than narrowly targeting the inner canthi, as recommended by the ISO guidelines. This insight could be helpful in establishing future directions with these devices, as full-face imaging is much easier to implement since it does not require complex facial feature detection software to identify the inner canthi regions. The next-best performance included the extended inner canthi area that includes but is wider than the inner canthi regions recommended by the ISO guidelines. Targeting the narrow canthi regions produced third-best accuracy.

FDA researchers calculated a series of cutoff levels to optimize the sensitivity and specificity values of the IRT readings. Although there is no uniform consensus on what temperature constitutes a fever, an oral temperature in the range of 37.5°C to 38°C (99.5°F to 100.4°F) is most commonly used in the medical profession as the threshold. The authors caution that determining an appropriate cutoff temperature for real-world fever screening involves complex considerations, such as the likely rate of false positives or negatives, as well as such matters as delay times, staffing, asymptomatic illness, and related costs to health agencies.

IRT-based fever screening

If conducted according to standardized protocols to ensure accuracy, IRT-based fever screening may effectively identify individuals with elevated body temperatures including low-grade fevers (oral temperature?37.5°C) associated with early-stage infections and moderate symptoms. According to Zane Arp, Director of the Division of Biomedical Physics at the FDA, "IRT-based fever screening, especially in regard to addressing COVID-19, should be one element in a multilayered diagnostic process that would include other helpful tools. When used in combination with other diagnostics and medical screening it is a much more useful tool in detecting those who are ill." For COVID-19 in particular, the FDA has published fact sheets on the proper use and limitations of these systems.

Given the potential value of IRTs for medical diagnostics, optimizing IRT-based fever screening is important, yet there remains much to learn. According to Wang, the FDA team plans further analysis to assess the potential impact of such factors as environmental and intersubject variability.
-end-
J. Biomedical Optics 25(9), 097002 (2020), doi 10.1117/1.JBO.25.9.097002.

SPIE--International Society for Optics and Photonics

Related Diagnostics Articles:

Study uses RNA sequencing as alternative to immunohistochemistry in cancer diagnostics
For the first time, researchers from the Moscow Institute of Physics and Technology and their colleagues have succeeded in using RNA sequencing as an alternative to immunohistochemistry for cancer diagnostics.
Rapid EUnetHTA assessment on coronavirus diagnostics supported by IQWiG
Rapid EUnetHTA assessment on coronavirus diagnostics supported by IQWiG. Antibody tests can detect a past infection with SARS Corona virus.
Inexpensive retinal diagnostics via smartphone
Retinal damage due to diabetes is now considered the most common cause of blindness in working-age adults.
Silver nanocubes make point-of-care diagnostics easier to read
Engineers at Duke University have shown that nanosized silver cubes can make diagnostic tests that rely on fluorescence easier to read by making them more than 150 times brighter.
Diagnostics, meet CRISPR
A new diagnostic test to quickly and easily monitor kidney transplant patients for infection and rejection relies on a simple urine sample and a powerful partner: the gene-editing technology CRISPR.
New platform for cancer diagnostics and drug testing
Parts of tumor tissue, which is normally discarded in cancer surgery, bear information about the disease.
Implementing microbiome diagnostics in personalized medicine: Rise of pharmacomicrobiomics
A new Commentary identifies three actionable challenges for translating pharmacomicrobiomics to personalized medicine in 2020.
Portable MRIs bring diagnostics to stroke patients' bedside
For the first time, portable, low-field MRIs have successfully imaged patients' brains to evaluate stroke at their bedside.
Moving diagnostics out of the lab and into your hand
Handheld electrochemical sensors have become part of the daily routine for millions of people who monitor their diabetes at home using inexpensive glucometers, but such technology has been difficult to adapt to other biomolecules.
Optoacoustic imaging shows potential for noninvasive diagnostics for thyroid disorders
A novel, noninvasive imaging technique can provide new information about thyroid disorders that will help in evaluation and diagnosis, according to an article featured in the October 2019 issue of The Journal of Nuclear Medicine.
More Diagnostics News and Diagnostics Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Debbie Millman: Designing Our Lives
From prehistoric cave art to today's social media feeds, to design is to be human. This hour, designer Debbie Millman guides us through a world made and remade–and helps us design our own paths.
Now Playing: Science for the People

#574 State of the Heart
This week we focus on heart disease, heart failure, what blood pressure is and why it's bad when it's high. Host Rachelle Saunders talks with physician, clinical researcher, and writer Haider Warraich about his book "State of the Heart: Exploring the History, Science, and Future of Cardiac Disease" and the ails of our hearts.
Now Playing: Radiolab

Insomnia Line
Coronasomnia is a not-so-surprising side-effect of the global pandemic. More and more of us are having trouble falling asleep. We wanted to find a way to get inside that nighttime world, to see why people are awake and what they are thinking about. So what'd Radiolab decide to do?  Open up the phone lines and talk to you. We created an insomnia hotline and on this week's experimental episode, we stayed up all night, taking hundreds of calls, spilling secrets, and at long last, watching the sunrise peek through.   This episode was produced by Lulu Miller with Rachael Cusick, Tracie Hunte, Tobin Low, Sarah Qari, Molly Webster, Pat Walters, Shima Oliaee, and Jonny Moens. Want more Radiolab in your life? Sign up for our newsletter! We share our latest favorites: articles, tv shows, funny Youtube videos, chocolate chip cookie recipes, and more. Support Radiolab by becoming a member today at Radiolab.org/donate.