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Does Dermal Thermography Have Utility In Podiatric Practice?

Windy Cole DPM

08/21/2020

A picture is worth a thousand words. How many times do we hear that saying? It rings true in many aspects of our daily clinical practice. Whether we are talking radiographs, magnetic resonance imaging (MRI), ultrasound or standard photos, medical imaging helps us diagnose, treat and monitor various medical conditions. New additions to our imaging arsenal include the emergence of small, portable, point-of-care imaging devices that can easily fit into clinical office settings.

Podiatrists are masters of observation. When performing a physical exam, our training tells us to look for discrepancies in tissue color, shape or consistency. Unfortunately, normal human vision limits us to a very small portion of the electromagnetic spectrum. One cannot detect thermal energy with the naked eye. It has a much longer wavelength than visible light. Infrared thermography is a diagnostic technology that lets clinicians and patients instantly visualize and verify thermal energy. Everything with a temperature above absolute zero emits heat. Even extremely cold objects such as ice will emit infrared energy. The greater an object’s temperature, the more intense the emission of infrared radiation.

Infrared thermography allows us to see what our naked eyes cannot detect. Infrared thermography cameras produce images of invisible infrared radiation based on heat and provide precise non-contact temperature measurement capabilities. As heat sensed by an infrared camera is precisely quantifiable, new applications for infrared cameras continue to emerge. One of the largest areas of growth appears to be in the health-care sector.

Thermal imaging devices can potentially provide information on systemic or local temperature abnormalities in tissue caused by ischemia, trauma, inflammation or infection prior to the onset of clinical manifestations. The technique consists of comparing images obtained on both limbs with performance of an asymmetrical analysis by subtracting the mean temperature of the non-affected limb from the corresponding value of the affected one.¹ Long-wave infrared thermography can measure radiant heat from a body surface and has long been accepted as a valuable adjunct to standard investigations in the early detection of inflammation and infection.1 Devices such as the FLIR ONE^® (FLIR^® Systems) thermal camera for smartphones easily attach to an existing cell phone and one utilizes an app to operate the thermal camera.

Case Study: When A Patient Experiences Right Fifth Toe Pain While Training For An Ultramarathon

A recent patient case report demonstrates the utility of this device in podiatric practice. A 54-year-old male with no significant past medical history presented with pain in the right fifth toe that began to develop during recent training for an ultramarathon. The physical exam revealed a mildly erythematous and edematous digit. The patient related a pain score of nine on the visual analog scale. The patient previously self-treated with foot soaks and antimicrobial creams without relief. The differential diagnosis included inflammation from repetitive trauma, stress fracture and infection.

The FLIR ONE thermal images of the toe showed that the right fifth toe "lights up" in comparison to the contralateral digit. After two days of oral antibiotic therapy, I obtained an additional thermal image of the right fifth toe. In this infrared image, the temperature appears to have normalized, indicating initial resolution of a prior infectious process. The patient’s pain had also began to abate.

In Conclusion

Ease of use and device cost are important considerations when implementing new imaging technologies into standard of care algorithms. Cell phone add-on devices such as the FLIR ONE thermal camera will make it easier for advanced imaging to gain acceptance across the board in many clinical settings. This device has the potential to help clinicians collect more accurate and objective data, thus allowing for better diagnosis and treatment of patients across the continuum of care.

Dr. Cole is the Medical Director of the Wound Care Center at University Hospitals Ahuja Medical Center in Beachwood, Ohio. She is also an Adjunct Professor and Director of Wound Care Research at the Kent State University School of Podiatric Medicine.

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