Use of Multimodal Long-Wave Infrared Thermography Devices in Clinical Practice

The assessment of wounds has historically included evaluation via visual and clinical presentation, with initial evaluation including the presence of pain, discoloration, redness, swelling, etc. In certain cases, only some or none of these parameters are present, and these cases can transform from acute and relatively treatable wounds to more insidious and chronic wounds. Diagnosis and treatment of chronic wounds in the United States has burdened the medical system with an estimated Medicare cost of $96.8 billion.¹ In addition, studies have even investigated quality of life in patients with chronic wounds, revealing site-specific needs but, more importantly, an overall diminished quality of life.^2-4 Researchers and clinicians are interested in defining more expeditious and affordable methods to assess and address wound management, which often requires utilizing an interdisciplinary approach.⁵ The only devices currently used for the potential management of wounds at the bedside are pulse oximetry (pulse-ox) and ultrasound doppler. Unfortunately, doppler assessment is operator dependent⁶ and pulse-ox technology is associated with a plethora of limitations that can compound potential sources and accuracy of determining wound integrity.⁷ Therefore, novel tools and methods of enhancing the interdisciplinary approach of addressing wound development that could be available to all levels of health care professionals are of vital importance. An example of this novel technology is a tool with diverse applications that can be optimized to help detect and monitor wounds: long-wave infrared thermography (LWIT) devices.

Infrared technology has been used for a long time in various fields. Firefighters utilize it to visualize people within large amounts of smoke, electricians use it to detect heat changes in power structures, and the military apply this technology to identify persons when given a field that may be difficult to assess. Infrared imaging technology uses relative changes in temperature reflected as thermograms via the detection of radiation in the long-infrared spectrum of the electromagnetic spectrum. Therefore, warmer objects in view of a LWIT device will emit and reflect a higher and brighter level of radiation (ie, temperature change) as compared with the environment around it including cooler skin, bedding, etc, which would appear bluish/black. The study of the use of this technology in patients is a relatively new concept. The first study of an LWIT showed these devices can provide reliable and consistent recordings,⁸ which is important for accurately tracking patient changes in their respective wounds. This work was important in setting a standard for the opportunity to adopt this technology into clinical practice; however, more work surrounding its efficacy at assessing healing in a predictable manner is needed.

The use of infrared devices is expected to sharpen the ability of clinicians to assess the quality of wounds. In a small cohort, Bilska et al recently showed the use of infrared thermography enhancing the predictability of the course of wound healing.⁹ Furthermore, researchers in Finland and the Netherlands have shown the utility in assessing severity and treatment of disease outcomes from peripheral artery disease and burn patients, respectively.^10,11 The findings from the studies establish a strong basis for the serious clinical investigation of the use of infrared technology in the care of patients with wounds. This technology could serve as a baseline for wound management, and it is therefore important to understand the scenarios in which it could be applied. This report will discuss several cases using an LWIT device to monitor for the signs and symptoms of wound infections, to evaluate the physiological status of a wound and the response to treatment, and to assess circulation and perfusion. Overall, the use of LWIT devices in these patients allowed clinicians to help drive optimal wound healing outcomes. 

This work is a retrospective case series performed via chart review of pertinent patients that the authors have encountered in clinical practice. Important history, procedures, and outcomes, as well as pictorial evidence, was pulled from the electronic medical records to give adequate information on each case.

Early Identification of Wound Infections

Patients are often treated with antibiotics postoperatively, but actual management and evaluation of a surgical site can be difficult as visual inspection alone is heavily relied upon to be the best and only indicator of indolent changes. A 55-year-old male patient had undergone a coronary bypass with a radial artery graft from the left arm. The patient had a history of hypertension, gout, stent placement to vertebral artery in 2011, and asplenia following a manual vacuum aspiration in 2012. The patient was seen in the office with chest pain and mild shortness of breath with activity. Six days later, the patient presented to the emergency department due to increased chest pain. There the patient was shown to have elevated troponins and ST changes on EKG. He then underwent cardiac catheterization revealing 4 vessel stenosis and was prepared for bypass using the mammary arteries and the left radial artery. Prior to surgery the patient was enrolled in a study to measure preoperative and postoperative temperature changes orally and using LWIT at the graph site (Figure 1A).

The patient was discharged on postoperative day (POD) 4. Postoperatively, the patient reported frequent changes in temperature measuring as low-grade fever highest at 99.7°F and with hot/cold flashes for several days. On POD 8, the patient was seen at a follow-up visit due to painful erythema on the left arm graft site (Figure 1B) and subsequently started on doxycycline 100mg twice a day and cephalexin 500 mg 4 times a day, both for 1 week. The patient’s temperature was recorded until POD 29 (Figure 1C).  

From the case presented, the visible incisional assessment did not show inflammation until POD 8. The measurements taken with the LWIT device showed greater than normal clinical inflammation starting POD 3, which was 5 days prior to visible assessment of redness appearing; thermal temperatures continued and increased until POD 9 (24 hours after antibiotics started). In following this patient post operation, the LWIT device recorded variances in extremity temperature to capture signs of infection earlier than conventional clinical methods. The opportunity to eradicate an infection early is important as it serves as a significant complication of many plastic surgery procedures including flap placement and general wound healing. The opportunity to determine and manage infections prior to the clinical evaluation can lead to more successful outcomes and diminish infection-related complications.

Detection of Insidious Infections 

Clinical suspicion based solely on visual input may result in inaccurate information and possible missed diagnosis of a patient’s true condition in a multitude of clinical scenarios. In this following case, a patient initially diagnosed with a superficial infection was revealed to have a severe infection ultimately requiring surgical management. 

A 57-year-old male patient was initially diagnosed with acute cellulitis of his left posterior thigh. Thermal readings were obtained via LWIT and revealed a larger, more severe change in temperature, suggesting a diagnosis of necrotizing fasciitis (Figure 2A). The patient was taken to surgery that day and underwent incision and debridement of the skin and deep tissues. He was placed on broad spectrum antibiotics. On POD 1, much of the wound returned to more homogenous readings, suggesting clearance of infection and inflammation (Figure 2B). POD 12 showed sustained healing of the wound (Figure 2C). The use of LWIT to aid in the redirection of a diagnosis is important in helping clinicians discern indolent infections from more severe or life-threatening ones. In this patient, specifically, it was important to identify necrotizing fasciitis early, as it has detrimental effects on the tissue with the unfortunate strong tendency to spread. This use of LWIT helped identify a more severe disease early and further aided in the documentation of clinical changes toward healing. It also helped the surgeon in preparedness for the surgery and understanding the extent of the infection.

Assessment of Established Therapies

In addition to cueing providers to intervene earlier in many cases, this technology also provides information as an adjunct indicator of the success of established wound therapies. The following 2 cases highlight the effects of hyperbaric oxygen (HBO) therapy and revascularization on 2 different wounds and the LWIT’s ability to assess healing.

The first case was a 59-year-old male patient with a chronic wound on his left lower extremity due to mixed vascular disease (Figure 3A). The patient underwent standard treatment for his wound, which unfortunately failed, and therefore, he was recommended for HBO therapy. After a session of HBO therapy, the patient exhibited a reduction in wound temperature, which was indicative of a successful treatment intervention (Figure 3B). This temperature reduction gradient can be visualized along the left lower anterior extremity. Other patients revealed similar trends in LWIT intensity post HBO treatment. This highlights the efficacy of LWIT to monitor the outcomes of wounds in a more objective manner when compared with visual inspection. This added information can help clinicians monitor treatment modalities for current and novel treatments that may not reveal significant clinical changes with visual evaluation alone. 

The next case follows a 78-year-old male diagnosed with pyoderma gangrenosum (PG) of the right lower extremity. He presented to the clinic with a poor ankle-brachial index and had undergone treatment with dialysis and lower extremity revascularization followed by standard wound care. After a few months receiving care at the wound clinic, PG was diagnosed and he began steroid therapy, and his wound began to be monitored via LWIT (Figure 4A). The patient exhibited high signal intensity throughout the limb prior to treatment. After 8 days of steroid treatment, the signal intensity throughout the limb was reduced (Figure 4B). This further validates the use of an LWIT device to observe and monitor treatment in patients undergoing standard therapy. Unfortunately, conventional measures of healing and progression in wounds are largely characterized by subjective assessments such as visual appearance of the wound. Capturing infrared changes allows clinicians to follow the course of a patient’s treatment and determine in advance changes needed to augment the healing course more meticulously. 

Assessment of Wound Integrity 

Wound integrity following any operation is a vital component of surgical follow up. The next patient is a 63-year-old with status post colorectal surgery who showed no visible signs or symptoms of infection or warning for incision dehiscence. The thermography images on POD 5 revealed an area of decreased temperature (Figure 5A) on the distal incision. The next day (POD 6), the follow-up image and assessment revealed the location of reduced temperatures was expanding in size (Figure 5B). The use of this technology allowed the providers to take a more proactive role in the evaluation of this patient with a developing wound and to prepare the patient for possible surgical exploration and debridement. This case highlights LWIT devices' utility to evaluate patients in a noninvasive manner, especially when there are no apparent signs of wound development.

Quantification and Visualization of Circulatory Integrity

As previously shown, LWIT devices are capable of monitoring wound healing progress in various modalities, but of critical importance in wound healing is the promotion of vascular integrity. In measuring temperature changes in wounds, we can begin to see early stages of revascularization. A prime example of this clinical application can be seen in the management of a 67-year-old male patient with a history of a diabetic foot ulcer (DFU) for 2 months. Attempts to revascularize failed, and therefore the patient underwent amputation and standard wound care (Figure 6A). Monitoring for changes in intensity during treatment revealed an increase in the signal intensity over the treatment period by 4°C (Figure 6B). The use of LWIT to monitor the healing of the DFU is indicative of an optimal noninvasive modality to ensure healing. This is important, as it can help guide any necessary changes in therapy components and time span based on relative factors of resolution. Determining vascular integrity is important, as it is a sign of proper healing. Utilization of the LWIT to monitor the revascularization of a wound can help solidify early treatment regiments and definitively mark the success of chronic wound without becoming invasive. Of note, one concern is that the increase in intensity could also be a sign of infection; therefore, other tools of assessment may be needed to determine if an increase in intensity is related to healing or infection. 

Visualization of Degree of Treatment/Revisional Modality for Wound 

The following patient is 67-year-old male with severe peripheral vascular disease status post failed left femoral popliteal bypass graft and below knee amputation (BKA). Due to circulatory deficiency, the BKA stump developed necrosis. Before using thermographic assessment, the physician recommended an above-the-knee amputation (AKA). The patient refused this recommendation and opted for a BKA. Post-BKA LWIT images revealed a demarcated temperature decrease on the surgical limb that was congruent with the physician’s assessment of poor circulation (Figure 7A); the evidence given by the LWIT device increased the patient’s compliance with the care plan. He then agreed to the original recommendation of AKA in hope of salvaging his remaining limb. Following the surgical revision, improved circulation was identified and was congruent with temperature increases (Figure 7B). The physician had been correct that an AKA would have been optimal, and this patient continued to have rapid healing of his wound. When used as an adjunct, temperature assessment may help improve patient compliance and determine the success of treatment outcomes such as amputation levels. The use of LWIT technology allows clinicians to help create long-term assessment plans, especially in cases that may present significant complications.

Early Identification of Deep Tissue Injury

Another valuable clinical application of LWIT devices can be found with the early identification of deep tissue injury (DTI).  Current practice is limited to visual examination to determine if DTI is present. The subjective nature of this assessment leaves much room for interpretation.¹² The use of LWIT can be crucial in identifying pressure injuries earlier than clinically visible. Additionally, LWIT allows clinicians to assess the development of DTI in high-risk patients staying in long-term care facilities.¹²

In this case, a 63-year-old male with multiple comorbidities was transferred from an acute care hospital to a long-term acute care facility.¹² This patient was unable to independently move himself or reposition in bed, leaving him prone to pressure injuries. On admission, the left heel was intact with no visible signs or symptoms of DTI. However, with use of the LWIT device, an isolated and demarcated bullseye-shaped area of inflammation consistent with DTI was found (Figure 8A). At follow-up 9 days later, the first visible sign of DTI appeared in this area as a painful purple spot with surrounding erythema (Figure 8B).¹²

Application in Monitoring Free Flaps

Another important clinical application for the use of LWIT devices has been seen in the monitoring of free flaps after reconstructive surgeries. This is a common point of stress after these operations, as intensive care unit-level motoring of flaps is necessary. To date this includes methods such as temperature, visual inspection, doppler, etc. However, the use of LWIT can augment this process by giving practitioners an objective measure to follow. 

In this case, a 65-year-old female required facial reconstruction after extensive excision of carcinoma affecting her right face. She successfully underwent a radial forearm fasciocutaneous free flap. After this operation, LWIT was used for monitoring of this flap, including thermal mapping representative of adequate perfusion (Figure 9).

With the use of the LWIT device, clinicians were able to provide supporting items to determine the success and/or progression of wound care treatment and vascular status. These results were detectable earlier than clinical changes in a wound that eventually required treatment. It may be important to have this early access to wound-specific changes so clinicians may more readily possess a way to identify signs of infection. In addition to monitoring rates of infection, this technology was also shown to reveal clinically significant improvement in wound care treatments. This quick and noninvasive assessment of wound healing can further confirm the success of the wound care plan. Next, these results showed that the LWIT can potentially be used to assess the revascularization of a wound and levels of amputations with predictive healing of the incision and level of amputation. And lastly, the value of LWIT devices in the early detection of deep tissue injuries was shown. These are all important considerations to help clinicians in the evaluation of wounds.

Furthermore, there are many appealing benefits that come with this technology: noninvasive objective assessment, quick and safe application with instant feedback, and cost. In a previous study, a savings of over $170,000 was extrapolated from earlier and more expeditious monitoring of 4 DTIs upon admission if they were properly identified and addressed with more aggressive offloading measures applied.¹² For facilities with patients at high risk for developing wounds, the use of this technology can result in significant savings in wound care-related complications and potential litigations.

While there are many exciting and promising applications for the use of this technology, there are also important limitations to consider. As with all new technologies, there is still much to be learned about LWIT’s full clinical potential.

Furthermore, as discussed, one of the main strengths of LWIT is its ability to give more objectivity to the physical exam of various conditions. Even so, there remains some subjectivity in interpreting the appearance of the thermal spectrum. Slightly different interpretations of the color given by the LWIT device are nevertheless a more objective measurement than typical clinical judgment of color or erythema. Future studies should include trying to reconcile this issue to give a completely objective measurement with LWIT. 

More research is needed to establish guidelines in which clinicians can appropriately and confidently use this technology to determine clinical significance in wound resolution, recurrence, or other complications. The use of LWIT as presented in these cases could serve as one noninvasive tool to monitor wound integrity. It is important to note that the limitations of this review include the use of individualized case reports as assessments to engage a novel concept in wound care. Future studies should be geared to assessing the (1) frequency of use of infrared technology in treating chronic wounds, (2) overall treatment outcomes in patients that have infrared technology as a function of their care, and (3) the quality of life in a statistically significant population of patients with chronic wounds. In addition, establishing a standard in the use of this technology is important in outlining short-term success of a treatment.

Current and future work will help lead the understanding of infrared technology in the assessment of perfusion demands in patients with acute or chronic wounds, grading tissue injury, and even assessing quality of therapy. There exists a strong need for this technology as it is safe, involves no contact, and is noninvasive while also being repeatable.⁸ In addition, minimal training is required for staff members to obtain the images, which could be used for assessment of individual and population-wide trends in tissue changes under the conditions discussed here as well as potentially others. It is the hope that the use of this technology will guide early, consistent, and quick clinical intervention and treatment for patients with chronic wounds leading to reduced health care costs and improved patient quality of life.

Affiliations: ¹University of Toledo, College of Medicine and Life Science, Department of Surgery, Toledo, Ohio; ²Wound Care Program, Jobst Vascular Institute, ProMedica Health Network, Toledo, Ohio; ³University of Toledo, College of Medicine and Life Sciences, Toledo, Ohio; ⁴Wayne State University School of Medicine, Detroit, Michigan; ⁵Natchitoches Regional Medical Center, Natchitoches, Louisiana

Correspondence: Richard Simman, MD, FACS; Richard.SimmanMD@ProMedica.org

Ethics: The imaging site attests that appropriate institutional guidelines were followed and informed patient consent was obtained for the use of photographs and case details included in this manuscript. All efforts have been made to de-identify the case images.

Disclosures: The authors disclose no financial or other conflicts of interest.