Thermography
Number: 0029
Table Of Contents
PolicyApplicable CPT / HCPCS / ICD-10 Codes
Background
References
Policy
Scope of Policy
This Clinical Policy Bulletin addresses thermography.
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Experimental and Investigational
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Aetna considers thermography (including digital infrared thermal imaging, magnetic resonance (MR) thermography and temperature gradient studies) experimental and investigational for all indications including the following (not an all-inclusive list) because available medical literature indicates that the effectiveness of thermography as a diagnostic technique has not been established:
- Assessment of free flap perforators in autologous breast reconstruction
- Assessment of myofascial trigger points
- Detection and screening for breast cancer
- Detection of brown adipose tissue activation
- Detection of rupture-prone vulnerable coronary plaque
- Determination of the efficacy of stroke rehabilitation
- Diagnosis of carpal tunnel syndrome
- Diagnosis of complex regional pain syndrome
- Diagnosis of deep tissue injury
- Diagnosis of musculoskeletal injuries
- Diagnosis and management of vasculitis
- Diagnosis of temporomandibular disorders
- Early identification of skin neoplasms
- Esophageal monitoring
- Evaluation and monitoring of individuals with Emery-Dreifuss muscular dystrophy
- Evaluation of acute skin toxicity of breast radiotherapy
- Evaluation of back and neck syndromes
- Evaluation of burn wounds
- Evaluation of degenerative joint diseases (e.g., osteoarthritis and rheumatic diseases)
- Evaluation of dry eye disease
- Evaluation of leprosy
- Evaluation of peripheral arterial disease
- Evaluation of systemic vasoconstriction and prognosis
- Joint assessment in individuals with inflammatory arthritis
- Management of infantile hemangioma
- Monitoring of diabetes mellitus
- Monitoring of remission in individuals with acute Charcot neuroarthropathy
- Pre- and peri-operative management of hidradenitis suppurativa
- Prediction and detection of pressure ulcers
- Prediction of lipo-abdominoplasty complications
- Prognosis of post-herpetic neuralgia
- Screening for adolescent idiopathic scoliosis.
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Aetna considers dynamic infrared blood perfusion imaging (DIRI) for intra-operative and post-operative perfusion assessment (e.g., assessment of skin blood perfusion in cranioplasty and flap evaluation) experimental and investigational because the effectiveness of these approaches has not been established.
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Related Policies
Background
Thermography
Thermography is the measurement of temperature variations at the body surface. The scientific evidence suggests that thermography may only confirm the presence of a temperature difference, and that other procedures are needed to reach a specific diagnosis. Thermography may add little to what doctors already know based on history, physical examination, and other studies.
Thermography studies are non-invasive imaging techniques that are intended to measure the skin surface temperature distribution of various organs and tissues. The infrared radiation from the tissues reveals temperature variations by producing brightly colored patterns on a liquid crystal display. Interpretation of the color pattern is thought to contribute to the diagnosis of many disorders including breast cancer, Raynaud's phenomenon, digital artery vasospasm, impaired spermatogenesis in infertile men, deep vein thrombosis, reflex sympathetic dystrophy/complex regional pain syndrome, vertebral subluxation, and others.
In contrast to the skin surface thermography techniques used by some chiropractors and other providers, a newer invasive test called a temperature gradient study involves an intravenous catheter. The catheter is threaded into the coronary arteries to directly measure temperature differences on the inner artery walls. Researchers believe this information may be related to the presence of unstable coronary artery plaques and could be useful in diagnosing vulnerable patients. Madjid et al (2006) have shown that inflamed atherosclerotic plaques are hot and their surface temperature correlates with an increased number of macrophages and decreased fibrous-cap thickness. Multiple animal and human experiments have shown that temperature heterogeneity correlates with arterial inflammation in vivo. Several coronary temperature mapping catheters are currently being developed and studied. These thermography methods can be used in the future to detect vulnerable plaques, potentially to determine patients' prognosis, and to study the plaque-stabilizing effects of different medications.
A number of medical authorities have concluded that thermography has no proven medical value, including the American Medical Association, the Office of Health Technology Assessment (OHTA), and the American Academy of Neurology. Based on a study by the OHTA, the Health Care Financing Administration (now the Center for Medicare and Medicaid Services) withdrew Medicare coverage of thermography.
Devices that have been used for thermography skin temperature differential analysis include the Nervoscope, the Temp-O-Scope, and the Neurocalometer.
There is insufficient evidence for the use of thermography for detection of breast cancer. A structured evidence review of thermography for breast cancer (Kerr, 2004) reached the following conclusions: "The evidence that is currently available does not provide enough support for the role of infrared thermography for either population screening or adjuvant diagnostic testing of breast cancer. The major gaps in knowledge at this time can only be addressed by large-scale, prospective randomised trials. More robust research on the effectiveness and costs of technologically advanced infrared thermography devices for population screening and diagnostic testing of breast cancer is needed, and the conclusions of this review should be revisited in the face of additional reliable evidence".
Other reviews have also found a need for additional research on thermography. Kennedy et al (2009) noted that thermography was first introduced as a screening tool for breast cancer in mid-1950s. However, after a 1977 study found thermography to lag behind other screening tools, the medical community lost interest in this diagnostic approach. These researchers discussed each screening tool with a focus brought to thermography. They stated that no single diagnostic tool provides excellent predictability; however, a combination that incorporates thermography may boost both sensitivity as well as specificity. The authors concluded that in light of technological advances and maturation of the thermographical industry, more research is needed to confirm the potential of thermography in providing an effective non-invasive, low-risk adjunctive tool for the early detection of breast cancer.
Mammography is currently the gold standard for breast cancer screening. Thus, sensitivities, specificities, as well as positive and negative predictive values of thermography need to be compared with those of mammography in order to ascertain if thermography is equivalent or superior to mammography. Presently, there is a lack of scientific data comparing the 2 screening techniques. In addition, there are no published evidence-based practice guidelines and/or position statements that recommend thermography as the appropriate method of screening for early detection of breast cancer.
Arora et al (2008) examined the effectiveness of a non-invasive digital infrared thermal imaging (DITI) system in the detection of breast cancer. A total of 92 patients for whom a breast biopsy was recommended based on prior mammogram or ultrasound underwent DITI. Three scores were generated:- an overall risk score in the screening mode,
- a clinical score based on patient information, and
- assessment by artificial neural network.
Sixty of 94 biopsies were malignant and 34 were benign. Digital infrared thermal imaging identified 58 of 60 malignancies, with 97 % sensitivity, 44 % specificity, and 82 % negative predictive value depending on the mode used. Compared to an overall risk score of 0, a score of 3 or greater was significantly more likely to be associated with malignancy (30 % versus 90 %, p < 0.03). The author concluded that DITI is a valuable adjunct to mammography and ultrasound, especially in women with dense breast parenchyma. Moreover, the authors reported a high negative predictive value for thermography where "the location of the lesion under question based on prior imaging was assessed to generate a positive or negative clinical assessment", i.e., where they were unblinded to the results of the prior mammography or ultrasound. The specificity was only 11 % and the negative predictive value of thermography was only 66 % in the blinded screening mode. Furthermore, the authors stated that DITI is not currently recommended or approved as a substitute for screening mammography, and correlation of findings on DITI should be made with alternative imaging techniques. They stated that further studies are needed using a representative screening population of persons who have not been selected for biopsy based upon prior imaging results.
An American Cancer Society report Mammograms and Other Breast Imaging Procedures (2010) stated that "[t]hermography is a way to measure and map the heat on the surface of the breast using a special heat-sensing camera. It is based on the idea that the temperature rises in areas with increased blood flow and metabolism, which could be a sign of a tumor. Thermography has been around for many years, and some scientists are still trying to improve the technology to use it in breast imaging. But no study has ever shown that it is an effective screening tool for finding breast cancer early. It should not be used as a substitute for mammograms. Newer versions of this test are better able to find very small temperature differences. They may prove to be more accurate than older versions, and are now being studied to find out if they might be useful in finding cancer". Thermography is listed under "newer and experimental breast imaging methods" in this report.
Additionally, the United Kingdom's NHS Cancer Screening Programmes (2010) stated that "thermography is not a replacement for mammography. It is a relatively new test and isn't reliable enough to use either to diagnose or screen for cancer. Mammography is still the best test and is used as a world wide standard for breast screening in women over 50".
The Food and Drug Administration (FDA, 2011) stated that breast thermography should not be used instead of mammography, noting that thermography has not been approved as a stand-alone tool for breast cancer screening or diagnosis. Telethermographic devices produce infrared images and do not require exposure to radiation or breast compression, which some healthcare providers claim make them superior to mammographic devices. However, the FDA stated that "there is simply no evidence" that breast thermography can take the place of mammography. The agency has sent warning letters to manufacturers and practitioners who have made misleading claims about breast thermography use.
Currently, there is insufficient evidence to support the use of thermography for the diagnosis of complex regional pain syndrome (CRPS). The use of thermography in the diagnosis of CRPS type 1 (CRPS1) is based on the presence of temperature asymmetries between the involved area of the extremity and the corresponding area of the uninvolved extremity. However, the interpretation of thermographical images is subjective and not validated for routine use. Huygen et al (2004) developed a sensitive, specific and reproducible arithmetical model as the result of computer-assisted infra-red thermography in patients with early stage CRPS1 in one hand. Eighteen patients with CRPS1 on one hand and 13 healthy volunteers were included in the study. The severity of the disease was determined by means of pain questionnaires [visual analogue scale (VAS) pain and McGill Pain Questionnaire], measurements of mobility (active range of motion) and edema volume. Asymmetry between the involved and the uninvolved extremities was calculated by means of the asymmetry factor, the ratio and the average temperature differences. The discrimination power of the 3 methods was determined by the receiver-operating curve (ROC). The regression between the determined temperature distributions of both extremities was plotted. Subsequently the correlation of the data was calculated. In normal healthy individuals the asymmetry factor was 0.91 (0.01) (SD), whereas in CRPS1 patients this factor was 0.45 (0.07) (SD). The performance of the arithmetic model based on the ROC curve was excellent. The area under the curve was 0.97 (p < 0.001), the sensitivity and specificity was 9 2% and 94 %, respectively. Furthermore, the temperature asymmetry factor was correlated with the duration of the disease and VAS pain.
Gradl and colleagues (2003) stated that CRPS1 represents a frequent complication following distal radial fractures. These investigators studied the value of clinical evaluation, radiography and thermography in the early diagnosis of CRPS1. A total of 158 patients with distal radial fractures were followed-up for 16 weeks after trauma. Apart from a detailed clinical examination 8 and 16 weeks after trauma, thermography and bilateral radiographs of both hands were carried out. At the end of the observation period 18 patients (11 %) were clinically identified as CRPS1. The severity of the preceding trauma and the chosen therapy did not influence the process of the disease. Sixteen weeks after trauma easy differentiation between normal fracture patients and CRPS1 patients was possible. Eight weeks after distal radial fracture clinical evaluation showed a sensitivity of 78 % and a specificity of 94 %. On the other hand, thermography (58 %) and bilateral radiography (33 %) revealed poor sensitivities. The specificity was high for radiography (91 %) and again poor for thermography (66 %). These authors concluded that the results of the study support the importance of clinical evaluation in the early diagnosis of CRPS1. Plain radiographs facilitate the diagnosis as soon as bony changes develop.
Arterial wall thermography has also been used to identify rupture-prone vulnerable coronary plaque. However, the clinical value of arterial thermography in interventional cardiology has not been established.
Schaar and colleagues (2007) noted that rupture of vulnerable plaques is the principal cause of acute coronary syndrome and myocardial infarction. Identification of vulnerable plaques is therefore essential to enable the development of treatment modalities to stabilize such plaques. Thermography is one of the several novel methods being examined for detecting vulnerable plaques. It evaluates the temperature heterogeneity as an indicator of the metabolic state of the plaque. The authors concluded that while several invasive and non-invasive techniques are currently under development to assess vulnerable plaques, none has proven its value in an extensive in-vivo validation and all have a lack of prospective data.
García-García and colleagues (2008) stated that thin-capped fibroatheroma is the morphology that most resembles plaque rupture. Detection of these vulnerable plaques in-vivo is essential to being able to study their natural history and evaluate potential treatment modalities and, therefore, may ultimately have an important impact on the prevention of acute myocardial infarction and death. The investigators reported that, currently, conventional grayscale intra-vascular ultrasound, virtual histology and palpography data are being collected with the same catheter during the same pullback. A combination of this catheter with either thermography capability or additional imaging, such as optical coherence tomography or spectroscopy, would be an exciting development. Intra-vascular magnetic resonance imaging also holds much promise. The investigators stated that, to date, none of the techniques described above has been sufficiently validated and, most importantly, their predictive value for adverse cardiac events remains elusive. The investigators concluded that very rigorous and well-designed studies are needed for defining the role of each diagnostic modality. Until researchers are able to detect in-vivo vulnerable plaques accurately, no specific treatment is warranted.
Madjid and colleagues (2006) stated that up to 2/3 of acute myocardial infarctions develop at sites of culprit lesions without a significant stenosis. New imaging techniques are needed to identify those lesions with an increased risk of developing an acute complication in the near future. Inflammation is a hallmark feature of these vulnerable/high-risk plaques. These investigators have demonstrated that inflamed atherosclerotic plaques are hot and their surface temperature correlates with an increased number of macrophages and reduced fibrous-cap thickness. They noted that animal and human studies have reported that temperature heterogeneity correlates with arterial inflammation in-vivo. Several coronary temperature mapping catheters are currently being developed. These thermographic methods can be used in the future to detect vulnerable plaques, potentially to ascertain patients' prognosis, and to examine the plaque-stabilizing effects of various pharmacotherapies.
Sharif and Murphy (2010) noted that critical coronary stenoses have been shown to contribute to only a minority of acute coronary syndromes and sudden cardiac death. Autopsy studies have identified a subgroup of high-risk patients with disrupted vulnerable plaque and modest stenosis. Consequently, a clinical need exists to develop methods to identify these plaques prospectively before disruption and clinical expression of disease. Recent advances in invasive as well as non-invasive imaging techniques have shown the potential to identify these high-risk plaques. The anatomical characteristics of the vulnerable plaque such as thin cap fibro-atheroma and lipid pool can be identified with angioscopy, high frequency intra-vascular ultrasound, intra-vascular magnetic resonance imaging (MRI), and optical coherence tomography. Efforts have also been made to recognize active inflammation in high-risk plaques using intra-vascular thermography. Plaque chemical composition by measuring electro-magnetic radiation using spectroscopy is also an emerging technology to detect vulnerable plaques. Non-invasive imaging with MRI, computed tomography, and positron emission tomography also holds the potential to differentiate between low-risk and high-risk plaques. However, at present none of these imaging modalities is able to detect vulnerable plaque nor have they been shown to definitively predict outcome. Nevertheless in contrast, there has been a parallel development in the physiological assessment of advanced athero-sclerotic coronary artery disease. Thus, recent trials using fractional flow reserve in patients with modest non flow-limiting stenoses have shown that deferral of percutaneous coronary intervention with optimal medical therapy in these patients is superior to coronary intervention. The authors concluded that further trials are needed to provide more information regarding the natural history of high-risk but non flow-limiting plaque to establish patient-specific targeted therapy and to refine plaque stabilizing strategies in the future.
There is insufficient evidence to support the use of thermography in post-herpetic neuralgia. Han and associates (2010) examined the usefulness of infrared thermography as a predictor of post-herpetic neuralgia (PHN). Infrared thermography was performed on the affected body regions of 110 patients who had been diagnosed with acute herpes zoster (HZ). Demographical data collected included age, gender, time of skin lesions onset, development of PHN, and co-morbidities. The temperature differences between the unaffected and affected dermatome were calculated. Differences greater than 0.6 degrees C for the mean temperature across the face and trunk were considered abnormal. The affected side was warmer in 35 patients and cooler in 33 patients than the contralateral side. A patient's age and disease duration affected treatment outcomes. However, the temperature differences were not correlated with pain severity, disease duration, allodynia, development of PHN, and use of anti-viral agents (p > 0.05). The authors concluded that a patient's age and disease duration are the most important factors predicting PHN progression, irrespective of thermal findings, and PHN can not be predicted by infrared thermal imaging.
An Agency for Healthcare Research and Quality's report on non-invasive diagnostic techniques for the detection of skin cancers (Parsons et al, 2011) listed thermography as one of the investigational diagnostic techniques for the detection of skin cancers.
Kontos et al (2011) determined the sensitivity and specificity of DITI in a series of women who underwent surgical excision or core biopsy of benign and malignant breast lesions presenting through the symptomatic clinic. Digital infrared thermal imaging was evaluated in 63 symptomatic patients attending a 1-stop diagnostic breast clinic. Thermography had 90 true-negative, 16 false-positive, 15 false-negative and 5 true-positive results. The sensitivity was 25 %, specificity 85 %, positive-predictive value 24 %, and negative-predictive value 86 %. The authors concluded that despite being non-invasive and painless, because of the low sensitivity for breast cancer, DITI is not indicated for the primary evaluation of symptomatic patients nor should it be used on a routine basis as a screening test for breast cancer.
The Canadian Agency for Drugs and Technologies in Health’s technology assessment on Infrared thermography for population screening and diagnostic testing for breast cancer” (Morrison, 2012) states that “No randomized controlled trials have been conducted that compare the effectiveness of thermography with mammography for screening in well women, and there is no evidence regarding the cost-effectiveness of thermography used for screening. Prospective cohort studies of symptomatic patients or patients with abnormal mammograms or ultrasounds do not provide the type of evidence needed to justify the use of thermography for breast screening. Results indicate that thermography performance is worse than mammography in terms of sensitivity, specificity, and predictive values; however, some of the studies’ authors have suggested there may be a role for thermography as an adjunct diagnostic test in some cases”.
Kim et al (2012) evaluated the accuracy of the size and location of the ablation zone produced by volumetric MRI-guided high-intensity focused ultrasound (HIFU) ablation of uterine fibroids on the basis of MR thermometric analysis and assessed the effects of a feedback control technique. A total of 33 women with 38 uterine fibroids were treated with an MR imaging-guided HIFU system capable of volumetric feedback ablation. Size (diameter times length) and location (3-D displacements) of each ablation zone induced by 527 sonications (with [n = 471] and without [n = 56] feedback) were analyzed according to the thermal dose obtained with MR thermometry. Prospectively defined acceptance ranges of targeting accuracy were ± 5 mm in left-right (LR) and cranio-caudal (CC) directions and ± 12 mm in antero-posterior (AP) direction. Effects of feedback control in 8- and 12-mm treatment cells were evaluated by using a mixed model with repeated observations within patients. Overall mean sizes of ablation zones produced by 4-, 8-, 12-, and 16-mm treatment cells (with and without feedback) were 4.6 mm ± 1.4 (standard deviation) × 4.4 mm ± 4.8 (n = 13), 8.9 mm ± 1.9 × 20.2 mm ± 6.5 (n = 248), 13.0 mm ± 1.2 × 29.1 mm ± 5.6 (n = 234), and 18.1 mm ± 1.4 × 38.2 mm ± 7.6 (n = 32), respectively. Targeting accuracy values (displacements in absolute values) were 0.9 mm ± 0.7, 1.2 mm ± 0.9, and 2.8 mm ± 2.2 in LR, CC, and AP directions, respectively. Of 527 sonications, 99.8 % (526 of 527) were within acceptance ranges. Feedback control had no statistically significant effect on targeting accuracy or ablation zone size. However, variations in ablation zone size were smaller in the feedback control group. The authors concluded that sonication accuracy of volumetric MRI-guided HIFU ablation of uterine fibroids appears clinically acceptable and may be further improved by feedback control to produce more consistent ablation zones.
Brkljacic et al (2013) noted that breast cancer is a common malignancy causing high mortality in women especially in developed countries. Due to the contribution of mammographic screening and improvements in therapy, the mortality rate from breast cancer has decreased considerably. An imaging-based early detection of breast cancer improves the treatment outcome. Mammography is generally established not only as diagnostic but also as screening tool, while breast ultrasound plays a major role in the diagnostic setting in distinguishing solid lesions from cysts and in guiding tissue sampling. Several indications are established for contrast-enhanced MRI. Thermography was not validated as a screening tool and the only study performed long ago for evaluating this technology in the screening setting demonstrated very poor results. The conclusion that thermography might be feasible for screening cannot be derived from studies with small sample size, unclear selection of patients, and in which mammography and thermography were not blindly compared as screening modalities. Thermography cannot be used to aspirate, biopsy or localize lesions pre-operatively since no method so far was described to accurately transpose the thermographic location of the lesion to the mammogram or ultrasound and to surgical specimen. The authors concluded that thermography cannot be proclaimed as a screening method, without any evidence whatsoever.
The Work Loss Data Institute’s guideline on “Low back -- lumbar & thoracic (acute & chronic)” (2013) listed thermography (infrared stress thermography) as one of the interventions/procedures that was considered, but is not recommended.
Sanchis-Sanchez et al (2014) noted that musculoskeletal injuries occur frequently. Diagnostic tests using ionizing radiation can lead to problems for patients, and infra-red thermal imaging could be useful when diagnosing these injuries. A systematic review was performed to determine the diagnostic accuracy of infra-red thermal imaging in patients with musculoskeletal injuries. A meta-analysis of 3 studies evaluating stress fractures was performed and found a lack of support for the usefulness of infra-red thermal imaging (including thermography) in musculoskeletal injuries diagnosis.
Dibai-Filho and Guirro (2015) reviewed recent studies published on the use of infra-red thermography (IRT) for the assessment of myofascial trigger points (MTrPs). A search of the MEDLINE, CINAHL, PEDro, and SciELO databases was carried out between November 2012 and January 2013 for articles published in English, Portuguese, or Spanish from the year 2000 to 2012. Because of the nature of the included studies and the purpose of this review, the analysis of methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies tool. The search retrieved 11 articles, 2 of which were excluded based on language (German and Chinese); 3 were duplicated in different databases, 1 did not use IRT for diagnostic purposes, and the other did not use IRT to measure the skin temperature. Thus, the final sample was made up of 4 observational investigations: 3 comparative studies and 1 accuracy study. The authors concluded that at present, there are few studies evaluating the accuracy and reliability of IRT for the diagnosis and assessment of MTrPs. Of the few studies present, there is no agreement on skin temperature patterns in the presence of MTrPs.
Burke-smith et al (2015) states that currently the only evidence-based adjunct to clinical evaluation of burn depth is laser Doppler imaging (LDI), although preliminary studies of alternative imaging modalities with instant image acquisition are promising. These researchers investigated the accuracy of IRT and spectrophotometric intracutaneous analysis (SIA) for burn depth assessment, and compared this to the current gold standard: LDI. They included a comparison of the 3 modalities in terms of cost, reliability and usability. These investigators recruited 20 patients with burns presenting to the Chelsea and Westminster Adult Burns Service. Between 48 hours and 5 days after burn, these researchers recorded imaging using- moorLDI2-BI-VR (LDI),
- FLIR E60 (IRT) and
- Scanoskin (SIA).
Subsequent clinical management and outcome was as normal, and not affected by the extra images taken. A total of 24 burn regions were grouped according to burn wound healing: group A healed within 14 days, group B within 14 to 21 days, and group C took more than 21 days or underwent grafting. Both LDI and IRT accurately determined healing potential in groups A and C, but failed to distinguish between groups B and C (p > 0.05). Scanoskin interpretation of SIA was 100 % consistent with clinical outcome. The authors concluded that FLIR E60 and Scanoskin both presented advantages to moorLDI2-BI-VR in terms of cost, ease-of-use and acceptability to patients. Infra-red thermography is unlikely to challenge LDI as the gold standard as it is subject to the systematic bias of evaporative cooling. At present, the LDI color-coded palette is the easiest method for image interpretation, whereas Scanoskin monochrome color-palettes are more difficult to interpret. However the additional analyses of pigment available using SIA may help more accurately indicate the depth of burn compared with perfusion alone. The authors suggested development of Scanoskin software to include a simplified color-palette similar to LDI and additional work to further investigate the potential of SIA as an alternative to the current gold standard.
Evaluation of Burn Wounds
Prindeze and associates (2015) noted that despite advances in perfusion imaging, burn wound imaging technology continues to lag behind that of other fields. Quantification of blood flow is able to predict time for healing, but clear assessment of burn depth is still questionable. Active dynamic thermography (ADT) is a non-contact imaging modality capable of distinguishing tissue of different thermal conductivities. Utilizing the abnormal heat transfer properties of the burn zones, these researchers examined if ADT was useful in the determination of burn depth in a model of early burn wound evaluation. Duroc pigs (castrated male; n = 3) were anesthetized, and 2 burns were created with an aluminum billet at 3 and 12 seconds. These contact times resulted in superficial partial and deep partial thickness burn wounds, respectively. Active dynamic thermography and laser Doppler imaging (LDI) imaging were performed every 30 minutes post-burn for a total of 5 imaging sessions ending 150 minutes post-burn. For ADT, imaging excitation was performed for 42 to 120 seconds with dual quartz-infrared lamps, and subsequent infrared image capture was performed for 300 seconds; MATLAB-assisted image analysis was performed to determine burn zone region of interest thermal relaxation and characteristic patterns. Laser Doppler imaging was performed with a moorLDI system, and biopsies were captured for histology following the 150-minute imaging session. Both ADT and LDI imaging modalities were able to detect different physical properties at 30, 60, 90, 120, and 150 minutes post-burn with statistical significance (p < 0.05). Resultant ADT cooling curves characterized greater differences with greater stimulation and a potentially more identifiable differential cooling characteristic. Histological analysis confirmed burn depth. The authors concluded that this preliminary work confirmed that ADT can measure burn depth and is deserving of further research either as a stand-alone imaging technology or in combination with a device to assess perfusion.
Burke-Smith and colleagues (2015) stated that the only evidence-based adjunct to clinical evaluation of burn depth is LDI, although preliminary studies of alternative imaging modalities with instant image acquisition are promising. These investigators examined the accuracy of IRT and spectrophotometric intracutaneous analysis (SIA) for burn depth assessment, and compared this to the current gold standard: LDI. They included a comparison of the 3 modalities in terms of cost, reliability and usability. These investigators recruited 20 patients with burns presenting to the Chelsea and Westminster Adult Burns Service. Between 48 hours and 5 days post-burn, these researchers recorded imaging using moorLDI2-BI-VR (LDI), FLIR E60 (IRT) and Scanoskin (SIA). Subsequent clinical management and outcome was as normal, and not affected by the extra images taken. A total of 24 burn regions were grouped according to burn wound healing: group A healed within 14 days, group B within 14 to 21 days, and group C took more than 21 days or underwent grafting. Both LDI and IRT accurately determined healing potential in groups A and C, but failed to distinguish between groups B and C (p > 0.05). Scanoskin interpretation of SIA was 100 % consistent with clinical outcome. The authors concluded that FLIR E60 and Scanoskin both presented advantages to moorLDI2-BI-VR in terms of cost, ease-of-use and acceptability to patients. Infrared thermography is unlikely to challenge LDI as the gold standard as it is subject to the systematic bias of evaporative cooling. At present, the LDI color-coded palette is the easiest method for image interpretation, whereas Scanoskin monochrome color-palettes are more difficult to interpret. However the additional analyses of pigment available using SIA may help more accurately indicate the depth of burn compared with perfusion alone. The authors suggested development of Scanoskin software to include a simplified color-palette similar to LDI, and additional work to further investigate the potential of SIA as an alternative to the current gold standard.
Jaspers and colleagues (2019) noted that reliable and valid assessment of burn wound depth or healing potential is essential to treatment decision-making, to provide a prognosis, and to compare studies evaluating different treatment modalities. These researchers compared and summarized the quality of relevant measurement properties of techniques that aim to assess burn wound depth or healing potential. They carried out a systematic literature search using PubMed, Embase and Cochrane Library. Two reviewers independently evaluated the methodological quality of included articles using an adapted version of the Consensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist. A synthesis of evidence was performed to rate the measurement properties for each technique and to draw an overall conclusion on quality of the techniques. A total of 36 articles were included, evaluating various techniques, classified as laser Doppler techniques; thermography or thermal imaging; other measurement techniques. Strong evidence was found for adequate construct validity of laser Doppler imaging (LDI). Moderate evidence was found for adequate construct validity of thermography, videomicroscopy, and spatial frequency domain imaging (SFDI). Only 2 studies reported on the measurement property reliability. Furthermore, considerable variation was observed among comparator instruments. The authors concluded that considering the evidence available, it appeared that LDI is currently the most favorable technique; thereby assessing burn wound healing potential. These researchers stated that additional research is needed into thermography, videomicroscopy, and SFDI to evaluate their full potential; future studies should focus on reliability and measurement error, and provide a precise description of which construct is aimed to measure.
Evaluation of Dry Eye Disease
Tan and colleagues (2016) evaluated the effectiveness of IR ocular thermography in screening for dry eye disease (DED); IR ocular thermography was performed on 62 dry eye and 63 age- and sex-matched control subjects. Marking of ocular surface and temperature acquisition was done using a novel “diamond” demarcation method. A total of 30 static- and 30 dynamic-metrics were studied and receiver operating characteristic curves were plotted. Effectiveness of the temperature metrics in detecting DED were evaluated singly and in combination in terms of their area under the curve (AUC), Youden's index and discrimination power (DP). Absolute temperature of the extreme nasal conjunctiva 5s and 10s after eye opening were best detectors for DED. With threshold value for the first metric set at 34.7° C, sensitivity and specificity was 87.1 % (95 % CI: 76.2 to 94.3 %) and 50.8 % (95 % CI: 37.9 to 63.6 %), respectively. With threshold value for the second metric set at 34.5°C, sensitivity and specificity was 77.6 % (95 % CI: 64.7 to 87.5 %) and 61.9 % (95 % CI: 48.8 to 73.9 %), respectively. The 2 metrics had moderate accuracy and limited performances with AUC of 72 % (95 % CI: 63 to 81 %) and 73 % (95 % CI: 64 to 82 %); Youden index of about 0.4 and DP of 1.07 and 1.05, respectively. None of the dynamic metrics was good detector for DED. Combining metrics was not able to increase the AUC. The authors concluded that the findings of this study suggested some utility for the application of IR ocular thermography for evaluation of patients with DED.
Evaluation of Leprosy
Cavalheiro and associates (2016) examined if IRT would be able to measure the change in temperature in the hands of people with leprosy. The study assessed 17 leprosy patients who were under treatment at the National Reference Center for Sanitary Dermatology and Leprosy, and 15 people without leprosy for the control group. The infrared camera FLIR A325 and Therma CAM Researcher Professional 2.9 software were used to measure the temperature. The room was air-conditioned, maintaining the temperature at 25° C; the distance between the camera and the limb was 70 cm. The vasomotor reflex of patients was tested by a cold stress on the palm. The study showed a significant interaction between the clinical form of leprosy and temperature, where the control group and the borderline-borderline form revealed a higher initial temperature, while borderline-lepromatous and lepromatous leprosy showed a lower temperature. Regarding vasomotor reflex, lepromatous leprosy patients were unable to recover the initial temperature after cold stress, while those with the borderline-tuberculoid form not only recovered but exceeded the initial temperature. The authors concluded that IRT proved a potential tool to assist in the early detection of neuropathies, helping in the prevention of major nerve damage and the installation of deformities and disabilities that are characteristic of leprosy.
Management of Infantile Hemangioma
In a preliminary, prospective, observational study, Burkes et al (2016) applied a functional imaging method, dynamic IRT, to investigate infantile hemangiomas (IH) status versus control skin and over time. A total of 25 subjects with superficial or mixed IHs (age of less than 19 months) over 59 clinic visits were included in this study. Infrared images of IHs and control sites, standardized color images, and three-dimensional (3D) images were obtained. Tissue responses following application and removal of a cold stress were recorded with video IRT. Outcomes included areas under the curve during cooling (AUCcool ) and rewarming (AUCrw ) and thermal intensity distribution maps. AUCcool and AUCrw were significantly higher and cooling rate slower for IHs versus uninvolved tissue indicating greater heat, presumably due to greater perfusion and metabolism for the IH. Infra-red distribution maps showed specific areas of high and low temperature. Significant changes in IH thermal activity were reflected in the difference (AUCcool - AUCrw ), with 6.2 at 2.2 months increasing to 37.6 at 12.8 months; IH cooling rate increased with age, indicating slower recovery, and interpreted as reduced proliferation and/or involution. The authors concluded that dynamic IRT was a well-tolerated, quantitative functional imaging modality appropriate for the clinic, particularly when structural changes, i.e., height, volume, color, were not readily observed. They stated that dynamic IRT may aid in monitoring progress, individualizing treatment, and evaluating therapies.
Monitoring of Diabetes Mellitus / Diabetic Foot Ulcer
Staffa et al (2016) stated that foot complications in persons with diabetes mellitus (DM) are associated with substantial costs and loss of quality of life. Increasing evidence suggests changes in skin temperature, measured using an IRT system, may be a predictor of foot ulcer development in patients with DM. In a case study, these researchers described the long-term IRT findings and overall clinical outcomes of a patient with DM and peripheral vascular disease (PVD). Foot temperature measurements using IRT were obtained slightly more than 1 year before and immediately following endovascular treatment of a 76-year old man, a non-smoker with type 2 DM, hypertension, and ischemic heart disease with cardiac arrhythmia. Although he was otherwise asymptomatic, the infrared measurement showed an average temperature difference of 2.3˚ C between the left and right foot until he developed a small, trauma-induced wound on the left foot, at which time left foot temperature increased. He was diagnosed with recto-sigmoid adenocarcinoma, underwent surgery and chemotherapy, and subsequently was evaluated for PVD. Before undergoing peripheral angiography and percutaneous transluminal angioplasty, IRT evaluation showed a hot spot on the left heel. Immediately following endovascular treatment, the mean temperature difference between the right and left foot was low (0.2˚ C), but a Stage I pressure ulcer was visible on the left heel. Skin breakdown in that area was observed 2 months later, and the wound continued to increase in size and depth. The patient died shortly thereafter due to complications of cancer. In this case study, a series of infrared images of foot skin temperatures appeared to show a relationship with blood circulation and wound/ulcer development and presentation. The authors concluded that IRT has the ability to instantaneously measure the absolute temperature of the skin surface over a large area without direct skin contact. However, they stated that these devices are very sensitive; and prospective clinical studies are needed to determine the validity, reliability, sensitivity, and specificity of these measurements for routine use in patients who are at risk for vascular disease and/or foot ulcers.
Petrova and colleagues (2020) examined the usefulness of monthly thermography and standard foot care to reduce diabetic foot ulcer recurrence. Individuals with diabetes (n = 110), neuropathy and history of greater than or equal to 1 foot ulcer participated in a multi-center, single-blind clinical trial. Feet were imaged with a novel thermal imaging device (Diabetic Foot Ulcer Prevention System). Subjects were randomized to intervention (active thermography + standard foot care [SOC]) or control (blinded thermography + SOC) and were followed-up monthly until ulcer recurrence or for 12 months. Foot thermograms of subjects from the intervention group were assessed for hot spots (areas with temperature greater than or equal to 2.2°C higher than the corresponding contralateral site) and acted upon as per local standards. After 12 months, 62 % of subjects were ulcer-free in the intervention group and 56 % in the control group. The odds ratios (ORs) of ulcer recurrence (intervention versus control) were 0.82 (95 % CI: 0.38 to 1.8; p = 0.62) and 0.55 (95 % CI: 0.21 to 1.4; p = 0.22) in uni-variate and multi-variate logistic regression analyses, respectively. The hazard ratios (HRs) for the time to ulcer recurrence (intervention versus control) were 0.84 (95 % CI: 0.45 to 1.6; p = 0.58) and 0.67 (95 % CI: 0.34 to 1.3; p = 0.24) in uni-variate and multi-variate Cox regression analyses, respectively. The authors concluded that monthly intervention with thermal imaging did not result in a significant reduction in ulcer recurrence rate or increased ulcer-free survival in this cohort at high-risk of foot ulcers. However, this trial has informed the design of a refined study with longer follow-up and group stratification, further aiming to examine the efficacy of thermography to reduce ulcer recurrence.
Predicting Pressure Ulcers
In a systematic review, Oliveira and colleagues (2017) examined the clinical significance of ultrasound (US), thermography, photography and sub-epidermal moisture (SEM) measurement in detecting skin/tissue damage and thus predicting the presence of pressure ulcers (PUs); determined the relative accuracy of one of these assessment methods over another; and made recommendations for practice pertaining to assessment of early skin/tissue damage. The following databases, Cochrane Wounds Group Specialized Register, the Cochrane Central Register of Controlled Trials, Ovid Medline, Ovid Embase, Elsevier version, Ebsco CINAHL, ClinicalTrials.gov , WHO International Clinical Trials Registry (ICTR) and The EU Clinical Trials Register were searched for terms including; thermography, ultrasound, sub-epidermal moisture, photograph and pressure ulcer. These investigators identified 4 SEM, 1 thermography and 5 ultrasound studies for inclusion in this review. Data analysis indicated that photography was not a method that allowed for the early prediction of PU presence; SEM values increased with increasing tissue damage, with the sacrum and the heels being the most common anatomical locations for the development of erythema and stage I PUs. Thermography identified temperature changes in tissues and skin that may give an indication of early PU development; however the data were not sufficiently robust; US detected pockets of fluid/edema at different levels of the skin that were comparable with tissue damage. Thus, SEM and US were the best methods for allowing a more accurate assessment of early skin/tissue damage. Using the EBL Critical Appraisal Tool, the validities of the studies varied between 33.3 to 55.6 %, meaning that there is potential for bias within all the included studies. All of the studies were situated at level IV, V and VII of the evidence pyramid. These researchers noted that although the methodological quality of the studies warrants consideration, these studies showed the potential that SEM and US have in early PU detection. The authors concluded that SEM and US are promising in the detection and prediction of early tissue damage and PU presence. However, they stated that these methods should be further studied to clarify their potential for use more widely in PU prevention strategies.
Determining the Efficacy of Stroke Rehabilitation
Hegedus (2018) stated that maintaining good physiological circulation in the extremities requires an optimally functioning muscle pump. Stroke symptoms indicate a change in venous circulation. In this study, these researchers measured changes in joint function and microcirculation, and the correlation between them. A total of 16 randomly selected post-stroke patients with hemiparesis affecting mainly the upper extremities began undergoing rehabilitation 13 ± 4 days following stroke. Thermograms were taken with a Fluke Ti 20 (Fluke Corporation, WA) pre-treatment and post-treatment, and a physiotherapy documentation form was completed. Treatment comprised 15 physiotherapy, massage, and galvanic therapy sessions per patient, with the side exhibiting no neurological symptoms as a control. Joint function showed significant improvement on the affected side (p < 0.05). Thermographic examinations revealed microcirculatory dysfunction in the affected extremities in 100 % of the cases. Following treatment, temperature increased significantly (p ≥ 0.5°C) on the affected side. A strong correlation (r) was observed between joint function and temperature change (p < 0.05). The authors concluded that thermography was shown to be a reliable method for monitoring the effects of stroke rehabilitation treatment. They stated that thermographic testing may enable clinicians to predict the course of the trauma and the effectiveness of treatment even at the acute stage.
Thermography for Evaluating Acute Skin Toxicity of Breast Radiotherapy
Maillot and associates (2018) stated that radiotherapy is a common adjuvant treatment of breast cancer. Acute radiation-induced dermatitis is a frequent side effect. These researchers hypothesized whether it is possible to capture the increase of local temperature as a surrogate of the inflammatory state induced by radiotherapy. They designed a prospective, observational, single-center study to acquire data on temperature rise in the treated breast during the course of radiotherapy, establish a possible association with the occurrence of dermatitis and examine the predictive value of temperature increase in future occurrences of radiation-induced dermatitis. All patients presenting for neoadjuvant or adjuvant radiotherapy during the course of breast cancer treatment at the university hospital of Martinique were considered for inclusion. Every week, patients were examined by 2 trained investigators for the occurrence of radiation-induced dermatitis, graded based on Radiotherapy Oncology Group, Common Terminology Criteria for Adverse Events v.4.0 and Wright scales. A frontal thermal image of torso was taken in strictly controlled conditions, with a calibrated TE-Q1 camera (Thermal Expert, i3systems, Daejeon, Korea). These investigators studied temperature differences between the irradiated breast or thoracic wall and the contralateral area. For each thermal picture, these researchers measured the difference in maximum temperature as well as the difference in minimum temperature and the difference in the average temperature in the considered area. They studied the evolution of these parameters over time (week after week), measuring the maximum recorded difference and its correlation to acute radiation dermatitis intensity. A total of 64 consecutive patients were included. For all patients, these investigators noticed an increase of temperature during the course of radiotherapy. Difference in maximum, minimum and average temperature was higher between the 2 breasts of patients with a radiation-induced dermatitis grade 2 or above compared to patients with no or mild dermatitis. Higher temperatures were also significantly associated with an increased sensation of discomfort, as recorded by questionnaire (p < 0.05). The authors concluded that as expected from the inflammatory phenomena involved in radiation-induced dermatitis, a noticeable increase in temperature during the course of radiotherapy was observed in all patients. Furthermore, high-grade radiation-induced dermatitis was strongly associated with an additional increase in local temperature, which was probably linked to the intense inflammatory reaction. Lastly, with a 1.4°C threshold set beforehand, it was possible to anticipate the occurrence of radiation-induced dermatitis, with interesting positive and negative predictive values (PPV and NPV) of 70 % and 77 %, respectively in this population. Moreover, these researchers stated that these findings need to be confirmed in a dedicated study.
Thermography for Evaluating and Monitoring of Individuals Emery-Dreifuss Muscular Dystrophy
Cabizosu and colleagues (2018) noted that Emery-Dreifuss muscular dystrophy (EDMD) is a clinical condition characterized by neuro-skeletal and cardiac impairments. By means of thermography, new insights could be obtained regarding the evaluation and follow-up of this disease. Actually, musculoskeletal disorders are a major cause of counseling and access to rehabilitation services and are some of the most important problems that affect the quality of life of many people. There are urgent clinical and research needs for the assessment and follow-up of patients with EDMD. These researchers offered a new possible hypothesis of validating thermographic techniques that support the evaluation and clinical follow-up of the EDMD. They relied on evidence of existing bibliography. These investigators performed a systematic review; and after the application of an automatic and manual filter, inclusion and exclusion criteria, no study was obtained. There is a lack of evidence on the use of thermography in EDMD. Due to a lack of information, these researchers expanded the search to studies concerning the use of thermography in relation to alterations of the musculoskeletal system compatible with those of EDMD, genetic diseases related to the X chromosome and more generally muscular atrophy. Based on other studies performed in diseases that showed signs and symptoms similar to EDMD, the authors believed that a new line of translational research could be opened with novel findings and they thought thermography could be an optimal tool for the clinical monitoring of this pathology. These researchers believed that it would be of a great importance to carry out an observational study, to lay the foundations for future work, that relate thermography to EDMD.
Thermography for Joint Assessment in Individuals with Inflammatory Arthritis
Jones and associates (2018) noted that rheumatoid arthritis (RA) is a common inflammatory disease that causes destruction of joints. Accurate recognition of active disease has significant implications in determining appropriate treatment; however, there is significant inter-rater variability in clinical joint assessment. In a cross-sectional study, these researchers evaluated the use of thermographic imaging in the evaluation of inflammatory arthritis activity as an adjunct to clinical assessment. This trial included 79 subjects recruited from the University of Alberta out-patient rheumatology clinic. These investigators compared the hand joints of 49 patients with RA diagnosed by American College of Rheumatology (ACR) criteria to 30 healthy volunteers. Convenience sampling of consecutive RA patients was undertaken. The effect of clinical assessment (HAQ and DAS-28) on joint temperature was evaluated using a linear mixed effect model. A thermography camera, FLIR T300 model, 30-Hz, was used to obtain both thermographic and digital images on subjects. Pearson's correlation coefficient was used to assess the correlation of clinical assessments and average joint temperature averaged over all joints. Thermographic analysis did not associate with clinical measures of disease activity. In RA patients, there was no statistically significant relationship between joint temperature and clinical assessment of disease activity including Health Assessment Questionnaire (coefficient estimate - 0.54, p = 0.056), swollen joints (coefficient estimate - 0.09, p = 0.238), or serologic markers of inflammation such as C-reactive protein (CRP; coefficient estimate - 0.006, p = 0.602) and erythrocyte sedimentation rate (ESR; coefficient estimate - 0.01, p = 0.503). The authors concluded that evaluation of disease activity requires a multi-faceted approach that includes clinical assessment and appropriate imaging. They stated that there may be a role for thermography in assessment of larger joints; however, it does not appear to be an effective modality for the small joints of the hand.
Thermography for Pre- and Peri-Operative Management of Hidradenitis Suppurativa
Derruau and co-workers (2018) stated that hidradenitis suppurativa (HS) is a chronic, inflammatory, and recurrent skin disease. Surgical excision of wounds appears to be the only curative treatment for the prevention of recurrence of moderate-to-severe stages; MRI is a standard reference examination for the detection of HS peri-anal inflammatory fistula. In this case study, the use of real-time medical infrared thermography (MIT), in combination with MRI as appropriate imaging, was proposed. The objective was to assist surgeons in the pre- and peri-surgical management of severe perianal HS with the intent to ensure that all diseased lesions were removed during surgery and therefore to limit recurrence. The results showed that MIT, combined with MRI, could be a highly effective strategy to address thermally distinguished health tissues and inflammatory sites during excision, as characterized by differential increases in temperature. Medical infrared thermography could be used to check the total excision of inflammatory lesions as a non-invasive method that is not painful, not radiant, and is easily transportable during surgery. The authors concluded that this method could be complementary with MRI in providing clinicians with objective data on the status of tissues below the perianal skin surface in the pre- and peri-operating management of severe HS. This was a single-case study; its findings need to be validated by well-designed studies.
Infrared Thermography for Diagnosis and Management of Vasculitis, Early Identification of Skin Neoplasms, Esophageal Monitoring, and Screening for Adolescent Idiopathic Scoliosis
Lin and colleagues (2018) noted that vasculitis is a clinical condition with associated diagnostic challenges due to non-specific symptoms and lack of a confirmatory imaging modality. These investigators reported a case of a 39-year old woman who developed generalized malaise, lethargy, and headache. Laboratory evaluation showed elevated inflammatory markers. Conventional imaging studies including computed tomography (CT) and carotid duplex ultrasound (US) were unremarkable. Infrared thermography revealed enhanced thermographic signals in the left carotid artery and aortic arch. Corticosteroid therapy was commenced, and the patient responded well. Follow-up infrared thermography at 6 months showed complete resolution of the thermographic pattern, and the patient remained symptom-free. The authors concluded that this case highlighted the potential clinical utility of using infrared thermography in patients with vasculitis. The enhanced thermal signals in the aortic arch and carotid artery provided valuable information in the diagnosis and treatment of arteritis in this patient. This technology was similarly beneficial in subsequent surveillance evaluation once the patient completed the prescribed treatment. Moreover, they stated that further studies are needed to determine the clinical sensitivity and diagnostic accuracy of this imaging modality in vasculitis.
Magalhaes and associates (2018) stated that infrared thermal imaging captures the infrared radiation emitted by the skin surface. The thermograms contain valuable information, since the temperature distribution can be used to characterize physiological anomalies. Thus, the use of infrared thermal imaging (IRT) has been studied as a possible tool to aid in the diagnosis of skin oncological lesions. These researchers evaluated the current state of the applications of IRT in skin neoplasm identification and characterization. They carried out a literature survey using the reference bibliographic databases: Scopus, PubMed and ISI Web of Science. Keywords (thermography, infrared imaging, thermal imaging and skin cancer) were combined and its presence was verified at the title and abstract of the article or as a main topic. Only articles published after 2013 were considered during this search. A total of 55 articles were encountered, resulting in 14 publications for revision after applying the exclusion criteria. It was denoted that IRT have been used to characterize and distinguish between malignant and benign neoplasms and different skin cancer types; IRT has also been successfully applied in the treatment evaluation of these types of lesions. The authors concluded that trends and future challenges have been established to improve the application of IRT in this field, disclosing that dynamic infrared thermography is a promising tool for early identification of oncological skin conditions.
Daly and co-workers (2018) noted that catheter ablation for atrial fibrillation (AF) has potential to cause esophageal thermal injury. Esophageal temperature monitoring during ablation is commonly used; however, it has not eliminated thermal injuries, possibly because conventional sensors have poor spatial sampling and response characteristics. To enhance understanding of temperature dynamics that may underlie esophageal injury, these researchers tested a high-resolution, intra-body, infrared thermography catheter to continuously image esophageal temperatures during ablation. Patients undergoing AF ablation were instrumented with a flexible, 9F infrared temperature catheter inserted nasally (n = 8) or orally (n = 8) into the esophagus adjacent to the left atrium. Ablation was performed while the infrared catheter continuously recorded surface temperatures from 7,680 points/sec circumferentially over a 6-cm length of esophagus. Physicians were blinded to temperature data. Endoscopy was performed within 24 hours to document esophageal injury. Thermal imaging showed that most patients (10/16) experienced greater than or equal to 1 events where peak esophageal temperature was over 40° C; 3 patients experienced temperatures over 50° C; and 1 experienced over 60 °C. Analysis of temperature data for each subject's maximum thermal event revealed high gradients (2.3 ± 1.4° C/mm) and rates of change (1.5 ± 1.3° C/sec) with an average length of esophageal involvement of 11.0 ± 5.4 mm. Endoscopy identified 3 distinct thermal lesions, all in patients with temperatures over 50° C; all resolved within 2 weeks. The authors concluded that infrared thermography provided dynamic, high-resolution mapping of esophageal temperatures during cardiac ablation. Esophageal thermal injury occurred with temperatures of over 50° C and was associated with large spatiotemporal gradients. Moreover ,they stated that additional studies are needed to determine the relationships between thermal parameters and esophageal injury.
In an editorial that accompanied the afore-mentioned study by Daly et al (2018), Borne and Nguyen (2018) stated that “it is important to note the multiple limitations of esophageal temperature monitoring. First, to be effective, esophageal monitoring must accurately reflect the esophageal temperature. The esophagus is a broad and patulous structure, and the position of a temperature probe might not align with the ablation catheter such that monitoring might provide a false sense of security. In a prior investigation in which 2 commercially available probes (9F esophageal probe and an 18F esophageal stethoscope) were used among patients undergoing ablation, there were significant differences in the peak temperature and rise in temperature between the probes, suggesting that significant temperature variation exists among frequently used temperature probes. Second, there is evidence to suggest that the use of a temperature probe can be potentially harmful. In an ex vivo model, ablation near a non-insulated multi-sensor esophageal probe significantly increased temperatures in the tissues adjacent to the ablation lesion compared with lesions without a nearby temperature probe. This was echoed in clinical work in which patients undergoing AF ablation were enrolled prospectively to receive an esophageal temperature probe-guided ablation strategy versus no temperature monitoring … The study has some notable limitations. First, there is limited validation of this technology for esophageal temperature monitoring. A previous report described the use of infrared probes to monitor esophageal temperatures in a swine model, which were significantly higher than conventional probes. The current authors reported their experience with the first-in-human use of the IRTC in a patient undergoing PVI. Rigorous ex vivo and in vivo experiments need to be performed, establishing best practices and limitations of this technology, including how distance and location of the IRTC and ablation catheter affect temperature readings, if interactions between radiofrequency ablation and the probe exist and correlations to multiple different conventional temperature probes. Second, lesions identified on endoscopy were not correlated to specific ablation lesions and their characteristics (i.e., contact force, force-time integral). To best define risk for esophageal injury and thereby allow for risk modification, ablation characteristics and IRTC esophageal temperatures need to be analyzed. For instance, is the risk of esophageal injury related to a time-temperature phenomenon, is it a structural/anatomic phenomenon, or is it related other factors that result in visible injury in some but not other ablation lesions causing temperatures >50° C? If lesions identified on endoscopy did not correlate to higher esophageal temperatures, it is hard to know how temperature monitoring would guide ablation … Although further work needs to be performed in establishing the use of infrared thermography, the authors should be commended on their work for developing a system that has the potential to provide useful temperature monitoring data to improve the safety of AF catheter ablation. Although the question remains as to what the optimal approach to avoid esophageal injury is, this study provides evidence to suggest that more accurate esophageal temperature monitoring is possible. Until then, we should remain on red alert for risks of esophageal injury, in order to keep catheter ablation safe”.
Kwok and colleagues (2017) stated that adolescent idiopathic scoliosis (AIS) is a multi-factorial, 3-D deformity of the spine and trunk. School scoliosis screening (SSS) is recommended by researchers as a means of early detection of AIS to prevent its progression in school-aged children. The traditional screening technique for AIS is the forward-bending test because it is simple, non-invasive and inexpensive. Other tests, such as the use of Moiré topography, have reduced the high false referral rates. These researchers examined the use of infrared (IR) thermography for screening purposes based on the findings of previous studies on the asymmetrical para-spinal muscle activity of scoliotic patients compared with non-scoliotic subjects; IR thermography was performed with an IR camera to determine the temperature differences in para-spinal muscle activity. A statistical analysis showed that scoliotic subjects demonstrated a statistically significant difference between the left and right sides of the regions of interest. This difference could be due to the higher IR emission of the convex side of the observed area, thereby creating a higher temperature distribution. The authors concluded that the findings of this study suggested the feasibility of incorporating IR thermography as part of SSS. Moreover, they stated that future studies could also consider a larger sample of both non-scoliotic and scoliotic subjects to further validate the findings.
Intraoperative Infra-Red Thermography in Surgery of Glioblastoma Multiforme
Naydenov and colleagues (2017) noted that IRT is a real-time non-contact diagnostic tool with a broad potential for neurosurgical applications. These researchers described the intraoperative use of this technique in a single patient with newly diagnosed glioblastoma multiforme (GBM). An 86-year old woman was admitted in the clinic with a 2-month history of slowly progressing left-sided paresis. Neuroimaging studies demonstrated an irregular space-occupying process consistent with a malignant glioma in the right fronto-temporo-insular region. An elective surgical intervention was performed by using 5-aminolevulinic acid fluorescence (BLUE 400, OPMI) and intraoperative IRT brain mapping (LWIR, 1.25 mRad IFOV, 0.05°C NETD). After dura opening, the cerebral surface appeared inconspicuous. However, IRT revealed a significantly colder area (Δt° 1.01°C), well corresponding to the cortical epicenter of the lesion. The underlying tumor was partially excised and the histological result was GBM. The authors concluded that intraoperative IRT appeared to be a useful technique for subcortical convexity brain tumor localization. Moreover, they stated that further studies with a large number of patients are needed to prove the reliability of this method in GBM surgery.
Dynamic Infrared Blood Perfusion Imaging
Dynamic infrared blood perfusion imaging (DIRI) is a new infrared imaging technique that is intended to detect changes in blood flow in tissue and organs by sensing passively emitted infrared radiation from tissues. Potential clinical applications of DIRI include: use as an adjunctive screening tool for breast cancer and other cancers; evaluation of response to cancer chemotherapy; monitoring response to therapy in diabetic peripheral vascular disease; identifying perforator vessels during pre-surgical planning; assessing post-operative perfusion of pedicle flaps following reconstructive surgery (i.e., of the breast); mapping of functional cortex in patients undergoing tumor surgery; and determining cardiac bypass graft patency and perfusion of the myocardium in cardiac surgery. Agostini and colleagues (2009) stated that dynamic infrared imaging is a promising technique in breast oncology. Currently available evidence, however, is limited to evaluations of DIRI's technical feasibility. There is an absence of evidence of the impact of DIRI on health outcomes. The BioScanIR System (OmniCorder Technologies, Inc., Bohemia, NY) is an example of a DIRI device that is commercially available.
Lohman et al (2015) stated that over the last decade, microsurgeons have used a greater variety of more complex flaps. At the same time, microsurgeons have also become more interested in technology, such as indo-cyanine green (ICG) angiography, dynamic infra-red thermography (DIRT), and photo-spectrometry, for pre-operative planning and post-operative monitoring. These technologies are now migrating into the operating room, and are used to optimize flap design and to identify areas of hypo-perfusion or problems with the anastomoses. Although relatively more has been published about ICG angiography, information is generally lacking about the intra-operative role of these techniques. A systematic analysis of articles discussing intra-operative ICG angiography, DIRT, and photo-spectrometry was performed to better define the sensitivity, specificity, expected outcomes, and potential complications associated with these techniques. For intra-operative ICG angiography, the sensitivity was 90.9 % (95 % confidence interval [CI]: 77.5 to 100) and the accuracy was 98.6 % (95 % CI: 97.6 to 99.7). The sensitivity of DIRT was 33 % (95 % CI: 11.3 to 64.6), the specificity was 100 % (95 % CI: 84.9 to 100), and the accuracy was 80 % (95 % CI: 71.2 to 89.7). The sensitivity of intra-operative photo-spectrometry was 92 % (95 % CI: 72.4 to 98.6), the specificity was 100 % (95 % CI: 98.8 to 100), and the accuracy was also 100 % (95 % CI: 98.7 to 100). The authors concluded that these technologies for intra-operative perfusion assessment have the potential to provide objective data that may improve decisions about flap design and the quality of microvascular anastomoses. However, more work is needed to clearly document their value.
Just and colleagues (2016) investigated static IRT and DIRT for intra- and post-operative free-flap monitoring following oropharyngeal reconstruction. A total of 16 patients with oropharyngeal reconstruction by free radial forearm flap were included in this prospective, clinical study. Prior ("intraop_pre") and following ("intraop_post") completion of the microvascular anastomoses, IRT was performed for intra-operative flap monitoring. Further IR images were acquired 1 day ("postop_1") and 10 days ("postop_10") after surgery for post-operative flap monitoring. Of the 16, 15 transferred free radial forearm flaps did not show any perfusion failure. A significant decreasing mean temperature difference (∆T: temperature difference between the flap surface and the surrounding tissue in Kelvin) was measured at all investigation points in comparison with the temperature difference at "intraop_pre" (mean values on all patients: ∆T intraop_pre = -2.64 K; ∆T intraop_post = -1.22 K, p < 0.0015; ∆T postop_1 = -0.54 K, p < 0.0001; ∆T postop_10 = -0.58 K, p < 0.0001). Intra-operative DIRT showed typical pattern of non-pathological rewarming due to re-established flap perfusion after completion of the microvascular anastomoses. The authors concluded that static and dynamic IRT is a promising, objective method for intra-operative and post-operative monitoring of free-flap reconstructions in head and neck surgery and to detect perfusion failure, before macroscopic changes in the tissue surface are obvious. They noted that a lack of significant decrease of the temperature difference compared to surrounding tissue following completion of microvascular anastomoses and an atypical re-warming following a thermal challenge are suggestive of flap perfusion failure.
Dynamic Infrared Blood Perfusion Imaging (DIRI) for Assessment of Skin Blood Perfusion in Cranioplasty
Rathmann and colleagues (2018) noted that complications in wound healing after neurosurgical operations occur often due to scarred dehiscence with skin blood perfusion disturbance. The standard imaging method for intra-operative skin perfusion assessment is the invasive indocyanine green video angiography (ICGA). The non-invasive dynamic infrared thermography (DIRT) is a promising alternative modality that was evaluated by comparison with ICGA. These researchers performed a proof-of-concept study for qualitative comparison of DIRT with the standard ICGA. This trial was carried out in 2 parts: investigation of technical conditions for intra-operative use of DIRT for its comparison with ICGA, and visual and quantitative comparison of both modalities in 9 patients. Time-temperature curves in DIRT and time-intensity curves in ICGA for defined regions of interest were analyzed. New perfusion parameters were defined in DIRT and compared with the usual perfusion parameters in ICGA. The visual observation of the image data in DIRT and ICGA showed that operation material, anatomical structures and skin perfusion were represented similarly in both modalities. Although the analysis of the curves and perfusion parameter values showed differences between patients, no complications were observed clinically. These differences were represented in DIRT and ICGA equivalently. The authors concluded that DIRT has shown a great potential for intra-operative use, with several advantages over ICGA. The technique is passive, contactless and non-invasive. The practicability of the intra-operative recording of the same operation field section with ICGA and DIRT has been demonstrated. These researchers stated that the promising results of this proof-of-concept provided a basis for a trial with a larger number of patients.
Diagnosis of Temporomandibular Disorders
de Melo and colleagues (2019) systematically reviewed the scientific efficacy of infrared thermography (IT) on the diagnosis of temporomandibular joint disorders (TMDs). These researchers carried out an electronic search in 8 databases for publications up to May 2018. Additionally, a hand-search of the reference lists was conducted. There were no restrictions on language or on year of publication. Two independent reviewers selected the studies, reviewed the abstract information, and assessed the quality. The methodology of the included articles was evaluated by using the QUADAS-2 tool. A total of 9 studies met the eligibility criteria and were included in the systematic review; 4 studies concluded that IT presented low accuracy or was not an accurate instrument for TMD diagnosis, however, there was substantial variation in sensitivity, specificity, and receiver operating characteristic curve values; 5 studies concluded that IT appeared to be promising or may be a complementary diagnostic aid in the evaluation of TMDs. These studies presented sensitivity values ranging from 70 % to 90 % and specificity values ranging from 62 % to 92 %. All studies were judged as being "at risk of bias" and as having "concerns regarding applicability". The authors concluded that the literature is still lacking in sufficient number of studies regarding the reliability of IT for the diagnosis of TMDs.
Assessment of Free Flap Perforators in Autologous Breast Reconstruction
Hennessy and Potter (2020) noted that perforator-based flaps have in recent years become the mainstay of autologous breast reconstruction practice. Imaging modalities ranging from Doppler US to CT angiography (CTA) demonstrate varying utility in the pre-operative identification and localization of perforators. Despite the availability of these radiological approaches, finding and quantitatively evaluating perforators remain a time-consuming and tedious process that is often complicated by a number of factors including variable anatomy before surgery and body habitus. Infra-red thermography (IRT) imaging showed promise as a novel modality for pre-operative localization of perforator vessels. These researchers stated that In flap planning and harvesting, IRT allowed for a non-ionizing, non-invasive method of examining perforator location and quality; therefore aided in surgical decision-making in real time. This may allow for higher quality and more efficient operations and potentially improve outcomes for patients; however, more experience and research with this technology is needed. Despite its historical roots, the fact that this technique is relatively novel in the surgical sphere meant that much more research is needed in the future, and IRT could become a standard component of free flap protocols. These researchers stated that future studies should include randomized controlled trials (RCTs) examining if short- and long-term flap outcomes are improved with IRT.
Berner et al (2021) noted that IRT allows the detection of infrared radiation that can be associated with skin temperature. Modern portable thermography devices have been used to identify the location of skin perforators by detecting subtle differences in skin temperature. These researchers carried out a diagnostic accuracy systematic review to determine the specificity and sensitivity of IRT. Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA)-compliant systematic review and meta-analysis was carried out, scrutinizing PubMed and Embase databases for diagnostic studies measuring the accuracy of IRT for perforator identification. Article screening, review and data gathering was performed in parallel by 2 independent authors. Eligible studies were subject to a formal risk of bias was assessment using the QUADAS2 instrument. A total of 254 entries were obtained, of which 7 satisfied the pre-established inclusion criteria. These studies reported a total of 435 perforators in 133 individuals. The most commonly examined locations were the antero-lateral thigh and abdominal wall. Reported sensitivity values ranged from 73.7 % to 100 %. A meta-analysis demonstrated a cumulative sensitivity of 95 %. Specificity was not routinely reported. All studies presented a moderate-to-high risk of bias according to QUADAS2. The authors concluded that IRT devices are an interesting alternative to traditional pre-operative investigations for perforator mapping. They are sensitive enough to identify a large proportion of perforators as "hot-spots"; however, there is limited evidence to estimate the specificity of this technology, as studies have failed to report true negative values associated with "cold-spots".
Monitoring of Remission in Individuals with Acute Charcot Neuroarthropathy
Gooday and colleagues (2020) noted that the management of acute Charcot neuroarthropathy relies on off-loading, which is costly and time-consuming. Published studies have employed monitoring techniques with unknown diagnostic precision to detect remission. In a systematic review, these researchers examined techniques for monitoring response to off-loading in patients with acute Charcot neuroarthropathy. They included studies of off-loading that examined or described monitoring techniques in acute Charcot neuroarthropathy. PubMed, Embase, CINAHL and Cochrane data-bases were searched (January1993 to July 2018). These investigators extracted data from papers including study design, setting, population, monitoring techniques and treatment outcomes. They also extracted information on the cost, clinical applicability, sensitivity and specificity, safety and participant acceptability of the monitoring techniques. These researchers screened a total of 1,205 titles, 140 abstracts and 45 full-texts, and included 29 studies. All studies were of low quality and at high risk of bias. In 7 studies, the primary objective was to examine monitoring techniques: 3 evaluated MRI, 2 thermography monitoring, 1 3-phase bone scanning and 1 Doppler spectrum analysis. The remaining 22 observational studies reported treatment outcomes and described the monitoring techniques used to examine the Charcot neuroarthropathy. Heterogeneity prevented the pooling of data. Very few studies included data on cost, clinical applicability, sensitivity and specificity, safety and patient acceptability of the monitoring techniques used. The authors concluded that multiple techniques have been used to determine remission in acute Charcot neuroarthropathy; however, uncertainty remains regarding their effectiveness. These researchers recommended further research into the influences of different monitoring techniques on treatment outcomes.
Detection of Brown Adipose Tissue Activation
Brasil and colleagues (2020) noted that brown adipose tissue (BAT) is an endocrine adipose tissue with attributes to dissipate energy as heat in response to changes in temperature and diet. Infrared thermography has been studied in recent years in the assessment of BAT thermogenesis, as an option to positron emission tomography-computed tomography (PET-CT), because of several advantages. These researchers carried out a systematic review on the use of IRT in BAT assessment. Comprehensive online search was carried out in different databases. The QUADAS 2 tool was used to examine studies' quality. A total of 12 studies met the inclusion criteria, whereas only 1 of these was considered of low risk of bias; 10 studies were favorable to IRT appliance in BAT evaluation, observing elevation of supra-clavicular skin temperature correlated with BAT activity. These researchers stated that studies were heterogeneous in design; thus, precluding a meta-analysis. They stated that further studies with similar methodologies are needed. The authors concluded that despite the large number of published methodologies, IRT is a promising method for detecting BAT activation.
Evaluation of Peripheral Arterial Disease
Wermelink and colleagues (2021) stated that many techniques have been introduced to enable quantification of tissue perfusion in patients with peripheral arterial disease (PAD). Currently, none of these techniques is widely used to analyze real time tissue perfusion changes during endovascular or surgical re-vascularization procedures. In a systematic review, these researchers provided an up-to-date overview of the peri-procedural applicability of currently available techniques, diagnostic accuracy of evaluating tissue perfusion and the relationship with clinical outcomes. This systematic review was carried out in accordance with the PRISMA guidelines; 4 electronic databases were searched up to December 31, 2020 for eligible articles: Medline, Embase, CINAHL and the Cochrane Central Register of Controlled Trials. Eligible articles describing a perfusion measurement technique, used in a peri-procedural setting before and within 24 hours after the re-vascularization procedure, with the aim of determining the effect of intervention in patients with PAD, were assessed for inclusion. The QUADAS-2 tool was used to assess the risk of bias and applicability of the studies. An overview of 10 techniques found in 26 eligible articles focused on study protocols, research goals, and clinical outcomes was provided. Non-invasive techniques included laser speckle contrast imaging (LSCI), micro-lightguide spectrophotometry, MRI perfusion, near infrared spectroscopy (NIRS), skin perfusion pressure (SPP), and plantar thermography (PT). Invasive techniques included two-dimensional (2D) perfusion angiography, contrast enhanced US (CEUS), CT perfusion imaging, and ICG angiography (ICGA). The results of the 26 eligible studies, which were mostly of poor quality according to QUADAS-2, were without exception, insufficient to substantiate implementation in daily clinical practice. The authors concluded that this systematic review provided an overview of 10 tissue perfusion assessment techniques for patients with PAD. These researchers stated that it appeared too early to appoint one of them as a reference standard; thus, the scope of future research in this domain should focus on clinical accuracy, reliability, and validation of the techniques.
Evaluation of Systemic Vasoconstriction and Prognosis
In a systematic review, Jensen and colleagues (2021) examined if IRT can measure systemic vasoconstriction and addresses the value of IRT in evaluating circulatory deficiency and prognoses. Experimental design was based on the PRISMA criteria and a systematic search of 6 databases was carried out. Of 3,198 records screened, 5 articles were included in the review – 3 clinical studies were identified; 2 found significant correlations between IRT obtained temperatures and mortality. An experimental study found an association between peripheral temperature and stroke volume. An animal study found that central-peripheral temperature differences correlated with shock index, mean arterial pressure (MAP), and disease progression. The authors concluded that data from the most valid study suggested that central-peripheral temperature differences should be further examined, both on its own, and integrated with other variables.
Prediction of Lipo-Abdominoplasty Complications
Resende and colleagues (2021) stated that the diagnosis of the main complications resulting from lipo-abdominoplasty has not yet been standardized. Infrared thermal imaging has been used to examine possible complications (e.g., necrosis and changes in micro- and macro-circulation) based on perforator mapping techniques, among others. These investigators presented 2 clinical cases entailing thermal imaging monitoring of the healing process of lipo-abdominoplasty in the immediate post-operative evaluation and its preliminary results. Infrared thermography was carried out 24 hours after the operation and on post-operative days 5, 25, and 27. In clinical case 1, it was found that the delta-R (∆TR)-defined as the difference in minimum temperature between the highest and lowest points in the SA3 region (caution suction area) following the classification established by Matarasso was 0.4°C at 24 hours after surgery and decreased to 0.1°C on post-operative day 5. There were no complications in this case. In contrast, in clinical case 2, the ∆TR was 1.7°C at 24 hours after surgery (upon hospital discharge) and remained high, at 2.2°C, on post-operative day 5. A higher ∆TR was found in the 2nd patient, who developed necrosis of the surgical wound. The authors concluded that based on the findings of this study, the proposed technique of thermal monitoring is promising as a new tool for predicting possible complications and complementing the clinical evaluation and therapeutic decision-making.Back and Neck Syndromes
Albuquerque and Lopes (2021) noted that thermography is a non-invasive method to detect temperature changes on or near the surface of the body. Despite its utility has not yet been fully verified, it may be used as a complementary method for screening and/or monitoring treatment effectiveness. In a systematic review, these investigators examined the role of IR thermography as an outcome measure tool in subjects with back and neck syndromes. They carried out a literature search using the National Library of Medicine (Medline), Web of Science and Scopus databases for studies that examined the role of IR thermography as an outcome measure tool in subjects with back and neck syndromes. The review was conducted according to the PRISMA protocol. The search strategy and selection criteria yielded 812 articles. From these, 268 duplicates were removed, and only 16 were in line with the objective of this review. Finally, only 7 precisely met the inclusion and exclusion criteria and were included in the review. According to the articles reviewed, thermography appeared to give an objective notion of change in inflammatory activity, which can corroborate the usefulness of treatment or the improvement/worsening of the patient's symptoms. The overall quality of research was uneven in the study design, endpoint measures, and sample characteristics. The authors concluded that the number of high-quality studies of the role of IR thermography in patients with back and neck syndromes remains limited.
Carpal Tunnel Syndrome
Becerra et al (2022) reported a thermal analysis of the wrists to analyze the behavior and recovery of skin temperature after 20 mins when performing a highly repetitive movement, and 2 thermography methods (sensory and IR) and research groups were compared. The tests were performed with 44 subjects who carried out a repetitive task for 10 mins and integrated into 2 groups, of which 22 were trained workers from a maquiladora company and were analyzed with sensory thermography, and the other 22 were in the laboratory with IR thermography with undergraduate students. The study area was the left and right hand, specifically the wrists. The proposed hypothesis was that individuals with some musculoskeletal problems have a reduction in temperature when starting repetitive tasks and thermal asymmetries, which measurements were recorded at 0, 10, 15, and 20 mins following the ending of the task. Results indicated that the temperatures in both wrists behaved similarly. The workers reached higher temperatures, and the centigrade degrees of asymmetry difference were also higher. The variable with influence on the temperature was fractured in the arm. After thermally analyzing the temperature behavior between the wrists of both hands, the authors concluded that there was an increase in temperature after finishing a repetitive task, and it did not stabilize after 20 mins. Both thermography methods observed that the asymmetries were greater than 0.5 °C, detecting the possible pathology of carpal tunnel syndrome (CTS). Moreover, these researchers stated that in future work, it is proposed to analyze how long it will take for the skin temperature to fully recover for healthy individuals as well as individuals with some assistive technology devices (ATDs) in the upper extremities. Likewise, it is proposed to analyze how many degrees of asymmetric difference exist between healthy subjects and subjects with some pathology. However, if in the study it is desired to know the temperature analyzed second by second, then sensory thermography is recommended, in addition to being more practical for evaluating operators within a company, since a deep protocol is not needed. However, IR thermography has advantages since it provides images of areas with higher temperatures, which can obtain the same data when analyzed.
Deep Tissue Injury
In a systematic review, Wynn et al (2022) examined the the available evidence regarding the risk factors for deep tissue injury (DTI) compared to grade I to IV pressure injury (PI), the proportion of DTI that evolve rather than resolve and the anatomical distribution of DTI. These investigators carried out a literature search using the Medline and CINAHL Plus databases using the search terms 'Deep tissue injury OR DTI [Title/abstract]'. A Google scholar search was also performed in addition to hand searches of relevant journals, websites and books that were identified from reference lists in retrieved articles. Only peer-reviewed English language articles published between 2009 and 2021 were included, with full text available online. The final qualitative analysis included 9 articles (4 retrospective studies, 4 prospective studies and 1 animal study). The authors concluded that the literature showed that the majority of DTI occurred at the heel and sacrum although in pediatric patients they are mainly associated with medical devices. Most DTI are reported to resolve, with between 9.3 % and 27 % deteriorating to full thickness tissue loss. Risk factors unique to DTI appeared to include anemia, vasopressor use, hemodialysis and nicotine use although it is unclear if these factors are unique to DTI or are shared with grade I to IV PI. Factors associated with deterioration include cooler skin measured using IR thermography and negative capillary refill. With 100 % of DTI showing positive capillary refill in 1 study resolving without tissue loss (p = 0.02) suggesting this may be an effective prognostic indicator. These researchers stated that more prospective studies are needed focusing on establishing causal links between risk factors identified in earlier retrospective studies. Ideally these should use statistically powered samples and sufficient follow-up periods allowing DTI outcomes to be reached. Moreover, they stated that further investigation is also needed to establish reliable diagnostic criteria for DTI in addition to more studies in the pediatric population.
Degenerative Joint Diseases
Schiavon et al (2021) noted that inflammation plays an important role in the pathophysiology of rheumatic diseases as well as in osteoarthritis (OA). Temperature, which can be quantified using IR thermography, provides information regarding the inflammatory component of joint diseases. In a systematic review, these investigators examined the potential and limitations of IR thermography in the evaluation of these pathologies. This systematic review was carried out using 3 major databases: PubMed, Cochrane library, and Web of Science, on clinical reports of any level of evidence in English language, published from 1990 to May 2021, with IR thermography used for diagnosis of OA and rheumatic diseases, monitoring disease progression, or response to treatment. Relevant data were extracted, collected in a database, and analyzed for the purpose of this systematic review. Of 718 screened articles, 32 were found to be eligible for inclusion, for a total of 2,094 patients. A total of 9 studies reported the application to OA, 21 to rheumatic diseases, 2 on both. The publication trend showed an increasing interest in the past 10 years; 7 studies examined the correlation of temperature changes with OA, 16 with rheumatic diseases, and 2 with both, whereas 2 focused on the pre-post evaluation to examine treatment results in patients with OA and 5 in patients with rheumatic diseases. A correlation was shown between thermal findings and disease presence and stage, as well as the clinical assessment of disease activity and response to treatment, supporting IR thermography role in the study and management of OA and rheumatic diseases. The authors concluded that the findings of this systematic literature review showed an increasing interest in this technology, with several applications in different joints affected by inflammatory and degenerative pathologies. A correlation was shown between thermal findings and disease presence and stage, as well as the clinical assessment of disease activity and response to treatment, supporting the potential role of IR thermography in the study and management of OA and rheumatic diseases.
The authors stated that the overall literature findings support the potential of using IR thermography for different joints and for both OA and rheumatic diseases to identify and classify the inflammatory component of the disease, as well as to monitor the treatment outcome. However, after decades of research, data are still based on a small number of patients for each clinical condition. Accordingly, the literature presents several drawbacks, which this systematic review reflected a small number of available studies reporting on a small number of patients. Furthermore, the heterogeneity of diseases treated in the studies and the different districts affected by pathology has hampered the possibility to conduct a meta-analysis. The different technologies and protocols used in the studies had been a further hindrance. In fact, this is an evolving field, starting from studies developing thermographic indexes, there are now different researchers relying on different patterns, indexes, and technological settings. However, even though the literature presents heterogeneous studies of low level, this systematic review still offered important indications, showing the feasibility and reliability of IR thermography as a complementary diagnostic tool in inflammatory and degenerative joints’ diseases. These findings could serve as a base for further studies toward the development of more specific high-level studies in which IR thermography is employed following specific protocols and guidelines to minimize possible bias, examine the real potential of this approach, and help to develop and improve IR thermography technologies.
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