Imaging of skin thermal properties with estimation of ambient radiation temperature

Thermography for disease detection in livestock: A scoping review

Infra-red thermography (IRT) offers potential opportunities as a tool for disease detection in livestock. Despite considerable research in this area, there are no common standards or protocols for managing IRT parameters in animal disease detection research. In this review, we investigate parameters that are essential to the progression of this tool and make recommendations for their use based on the literature found and the veterinary thermography guidelines from the American Academy of Thermology. We analyzed a defined set of 109 articles concerned with the use of IRT in livestock related to disease and from these articles, parameters for accurate IRT were identified and sorted into the fields of camera-, animal- or environment-related categories to assess the practices of each article in reporting parameters. This review demonstrates the inconsistencies in practice across peer-reviewed articles and reveals that some important parameters are completely unreported while others are incorrectly captured and/or under-represented in the literature. Further to this, our review highlights the lack of measured emissivity values for live animals in multiple species. We present guidelines for the standards of parameters that should be used and reported in future experiments and discuss potential opportunities and challenges associated with using IRT for disease detection in livestock.

Toward an Accurate IR Remote Sensing of Body Temperature Radiometer Based on a Novel IR Sensing System Dubbed Digital TMOS

A novel uncooled thermal sensor based on a suspended transistor, fabricated in standard CMOS-SOI process, and released by dry etching, dubbed Digital TMOS, has been developed. Using the transistor as the sensing element has advantages in terms of internal gain, low power, low-cost technology, and high temperature sensitivity. A two channel radiometer, based on the new nano-metric CMOS-SOI-NEMS Technology, enables remote temperature sensing as well as emissivity sensing of the forehead and body temperatures of people, with high accuracy and high resolution. Body temperature is an indicator of human physiological activity and health, especially in pediatrics, surgery, and general emergency departments. This was already recognized in past pandemics such as SARS, EBOLA, and Chicken Flu. Nowadays, with the spread of COVID-19, forehead temperature measurements are used widely to screen people for the illness. Measuring the temperature of the forehead using remote sensing is safe and convenient and there are a large number of available commercial instruments, but studies show that the measurements are not accurate. The surface emissivity of an object has the most significant effect on the measured temperature by IR remote sensing. This work describes the achievements towards high–performance, low-cost, low power, mobile radiometry, to rapidly screen for fever to identify victims of the coronavirus (COVID-19). The main two aspects of the innovation of this study are the use of the new thermal sensor for measurements and the extensive modeling of this sensor.

Skin Cancer Detection Using Infrared Thermography: Measurement Setup, Procedure and Equipment

Infrared thermography technology has improved dramatically in recent years and is gaining renewed interest in the medical community for applications in skin tissue identification applications. However, there is still a need for an optimized measurement setup and protocol to obtain the most appropriate images for decision making and further processing. Nowadays, various cooling methods, measurement setups and cameras are used, but a general optimized cooling and measurement protocol has not been defined yet. In this literature review, an overview of different measurement setups, thermal excitation techniques and infrared camera equipment is given. It is possible to improve thermal images of skin lesions by choosing an appropriate cooling method, infrared camera and optimized measurement setup.

Heat Emitting Damage in Skin: A Thermal Pathway for Mechanical Algesia

Mechanical pain (or mechanical algesia) can both be a vital mechanism warning us for dangers or an undesired medical symptom important to mitigate. Thus, a comprehensive understanding of the different mechanisms responsible for this type of pain is paramount. In this work, we study the tearing of porcine skin in front of an infrared camera, and show that mechanical injuries in biological tissues can generate enough heat to stimulate the neural network. In particular, we report local temperature elevations of up to 24°C around fast cutaneous ruptures, which shall exceed the threshold of the neural nociceptors usually involved in thermal pain. Slower fractures exhibit lower temperature elevations, and we characterise such dependency to the damaging rate. Overall, we bring experimental evidence of a novel—thermal—pathway for direct mechanical algesia. In addition, the implications of this pathway are discussed for mechanical hyperalgesia, in which a role of the cutaneous thermal sensors has priorly been suspected. We also show that thermal dissipation shall actually account for a significant portion of the total skin's fracture energy, making temperature monitoring an efficient way to detect biological damages.

Digital foot health technology and diabetic foot monitoring: A systematic review

BACKGROUND

In diabetic foot ulceration, a correlation between pressure and skin temperature is suspected. The aim of this systematic review is to provide a more rigorous analysis of existing literature related to the various technologies used to read and measure both in-shoe plantar pressures, and in-shoe skin temperatures simultaneously.

METHODS

A systematic review of the literature related to the topic was searched in database sources such as Medline OVID, Cochrane Library, PubMed, CONAHL, PROSPERO, and Elsevier. Outcome measures of interest included validity, reliability and responsiveness of in-shoe temperature and/or pressure mapping device used, and characteristics and quantity of sensors used, anatomical landmarks and statistical analysis used to interpret the data. Quality of evidence and risk of bias was evaluated using the QUADAS-2.

RESULTS

Nineteen studies were identified and included in this review. The majority of studies used a small sample size (mean n = 17) and recruited healthy participants. All studies have shown excellent validity but only a few tested for the reliability of the device. None of the studies tested for responsiveness of the device. Quality assessment results scored high risk in view of 'patient selection', 'use of reference standard' and 'applicability', and low risk in view of 'use if index test' and 'flow and timing'.

CONCLUSIONS

The data outlined in this review confirms that further improvement, reliability testing and clinical validation of the developed systems is required despite the results of excellent performance in detecting changes of in-shoe skin temperature and pressure.

The identification of higher forefoot temperatures associated with peripheral arterial disease in type 2 diabetes mellitus as detected by thermography

AIMS

The purpose of this study was to investigate whether heat emitted from the feet of patients with type 2 diabetes (DM) and peripheral arterial disease (PAD) differed from those with type 2 diabetes without complications (DM).

METHODS

A non-experimental, comparative prospective study design was employed in a tertiary referral hospital. Out of 223 randomly selected participants (430 limbs) who were initially tested, 62 limbs were categorized as DM+PAD and 22 limbs as DM without PAD. Subjects with evidence of peripheral neuropathy were excluded. Participants underwent thermographic imaging. Automatic segmentation of regions of interest extracted the temperature data.

RESULTS

A significant difference in temperature in all the toes between the two groups was found (p=0.005, p=0.033, p=0.015, p=0.038 and p=0.02 for toes 1-5 respectively). The mean forefoot temperature in DM+PAD was significantly higher than that in DM (p=.019), with DM+PAD having a higher mean temperature (28.3°C) compared to DM (26.2°C). Similarly, the toes of subjects with DM+PAD were significantly warmer than those of subjects with DM only.

CONCLUSIONS

Contrary to expectations the mean toe and forefoot temperatures in DM patients with PAD is higher than in those with DM only. This unexpected result could be attributed to disruption of noradrenergic vasoconstrictor thermoregulatory mechanisms with resulting increased flow through cutaneous vessels and subsequent increased heat emissivity. These results demonstrate that thermography may have potential in detecting PAD and associated temperature differences.

Establishing Differences in Thermographic Patterns between the Various Complications in Diabetic Foot Disease

AIM

To evaluate the potential of thermography as an assessment tool for the detection of foot complications by understanding the variations in temperature that occur in type 2 diabetes mellitus (DM).

METHODS

Participants were categorized according to a medical examination, ankle brachial index, doppler waveform analysis, and 10-gram monofilament testing into five groups: healthy adult, DM with no complications, DM with peripheral neuropathy, DM with neuroischaemia, and DM with peripheral arterial disease (PAD) groups. Thermographic imaging of the toes and forefeet was performed.

RESULTS

43 neuroischaemic feet, 41 neuropathic feet, 58 PAD feet, 21 DM feet without complications, and 126 healthy feet were analyzed. The temperatures of the feet and toes were significantly higher in the complications group when compared to the healthy adult and DM healthy groups. The higher the temperatures of the foot in DM, the higher the probability that it is affected by neuropathy, neuroischaemia, or PAD.

CONCLUSIONS

Significant differences in mean temperatures exist between participants who were healthy and those with DM with no known complications when compared to participants with neuroischaemia, neuropathy, or PAD. As foot temperature rises, so does the probability of the presence of complications of neuropathy, neuroischaemia, or peripheral arterial disease.

An instantaneous approach for determining the infrared emissivity of swine surface and the influencing factors

Infrared thermal imaging technology has been widely employed in temperature measurements of human and animals and its accuracy relies on the determination process of the emissivity of the target to a large extent. However, common used methods were unable to determine the emissivity of the surface of living animals and thus lower the accuracy. In this paper, we suggested a new approach to acquire the infrared emissivity of living swine in real time. In the approach, the surface temperature of swine and reference body were measured to compute the emissivity and the measurement process was completed in a non-contact and non-invasive manner. We changed the surface reflection energy of animals and reference body by changing the ambient radiant energy and obtain the surface emissivity in real time without confirming the actual temperature of animal surface. In this way, the infrared emissivity of the animal surface can be determined instantaneously and without knowing the real temperature. Both swine specimen and a living swine were used in this study. Using this method, we measured the emissivity of different body sites of the swine. The results showed that the emissivity values at different body sites show the significant differences. The emissivity values at trotter and eye were respectively 0.895 and 0.930 and the emissivity on swine surface varied from 0.945 to 0.978. More important, the distribution of the infrared emissivity on a living swine was explored and the detailed differences of the emissivity on a swine surface can be cleanly seen. Furthermore, we studied the influencing factors on the emissivity of animal surface, through measuring the emissivity distribution on swine surface when pig specimens were sprayed with water on the surface or heated using this method. This study is of great significance for the accurate measurement of swine surface temperature.

An Essential Role of NRF2 in Diabetic Wound Healing

The high mortality and disability of diabetic nonhealing skin ulcers create an urgent need for the development of more efficacious strategies targeting diabetic wound healing. In the current study, using human clinical specimens, we show that perilesional skin tissues from patients with diabetes are under more severe oxidative stress and display higher activation of the nuclear factor-E2-related factor 2 (NRF2)-mediated antioxidant response than perilesional skin tissues from normoglycemic patients. In a streptozotocin-induced diabetes mouse model, Nrf2(-/-) mice have delayed wound closure rates compared with Nrf2(+/+) mice, which is, at least partially, due to greater oxidative DNA damage, low transforming growth factor-β1 (TGF-β1) and high matrix metalloproteinase 9 (MMP9) expression, and increased apoptosis. More importantly, pharmacological activation of the NRF2 pathway significantly improves diabetic wound healing. In vitro experiments in human immortalized keratinocyte cells confirm that NRF2 contributes to wound healing by alleviating oxidative stress, increasing proliferation and migration, decreasing apoptosis, and increasing the expression of TGF-β1 and lowering MMP9 under high-glucose conditions. This study indicates an essential role for NRF2 in diabetic wound healing and the therapeutic benefits of activating NRF2 in this disease, laying the foundation for future clinical trials using NRF2 activators in treating diabetic skin ulcers.

Three-dimensional and thermal surface imaging produces reliable measures of joint shape and temperature: a potential tool for quantifying arthritis

Introduction

The assessment of joints with active arthritis is a core component of widely used outcome measures. However, substantial variability exists within and across examiners in assessment of these active joint counts. Swelling and temperature changes, two qualities estimated during active joint counts, are amenable to quantification using noncontact digital imaging technologies. We sought to explore the ability of three dimensional (3D) and thermal imaging to reliably measure joint shape and temperature.

Methods

A Minolta 910 Vivid non-contact 3D laser scanner and a Meditherm med2000 Pro Infrared camera were used to create digital representations of wrist and metacarpalphalangeal (MCP) joints. Specialized software generated 3 quantitative measures for each joint region: 1) Volume; 2) Surface Distribution Index (SDI), a marker of joint shape representing the standard deviation of vertical distances from points on the skin surface to a fixed reference plane; 3) Heat Distribution Index (HDI), representing the standard error of temperatures. Seven wrists and 6 MCP regions from 5 subjects with arthritis were used to develop and validate 3D image acquisition and processing techniques. HDI values from 18 wrist and 9 MCP regions were obtained from 17 patients with active arthritis and compared to data from 10 wrist and MCP regions from 5 controls. Standard deviation (SD), coefficient of variation (CV), and intraclass correlation coefficients (ICC) were calculated for each quantitative measure to establish their reliability. CVs for volume and SDI were <1.3% and ICCs were greater than 0.99.

Results

Thermal measures were less reliable than 3D measures. However, significant differences were observed between control and arthritis HDI values. Two case studies of arthritic joints demonstrated quantifiable changes in swelling and temperature corresponding with changes in symptoms and physical exam findings.

Conclusion

3D and thermal imaging provide reliable measures of joint volume, shape, and thermal patterns. Further refinement may lead to the use of these technologies to improve the assessment of disease activity in arthritis.

Thermography and thermometry in the assessment of diabetic neuropathic foot: a case for furthering the role of thermal techniques

There are currently 3 established techniques employed routinely to determine the risk of foot ulceration in the patient with diabetes mellitus. These are the assessment of circulation, neuropathy, and foot pressure. These assessments are widely used clinically as well as in the research domain with an aim to prevent the onset of foot ulceration. Routine neuropathic evaluation includes the assessment of sensory loss in the plantar skin of the foot using both the Semmes Weinstein monofilament and the biothesiometer. Thermological measurements of the foot to assess responses to thermal stimuli and cutaneous thermal discrimination threshold are relatively uncommon. Indeed, there remains uncertainty regarding the importance of thermal changes in the development of foot ulcers. Applications of thermography and thermometry in lower extremity wounds, vascular complications, and neuropathic complications have progressed as a result of improved imaging software and transducer technology. However, the uncertainty associated with the specific thermal modality, the costs, and processing times render its adaptation to the clinic. Therefore, wider adoption of thermological measurements has been limited. This article reviews thermal measurement techniques specific to diabetic foot such as electrical contact thermometry, cutaneous thermal discrimination thresholds, infrared thermography, and liquid crystal thermography.

Assessing foot temperature using infrared thermography

BACKGROUND

Previous reports recommended using skin temperature as a guide to monitor neuropathic feet during their rehabilitation course. However, the diagnostic usefulness was limited because of poor thermal measurement and procedures. The purpose of this study was to propose a standardized protocol to quantify foot temperature.

METHODS

An infrared image system was used to measure skin temperature. The first experiment was conducted on 16 healthy volunteers to study temperature variation with respect to time. This study mapped out six subregions of anatomic interest over the sole, and average temperature values for each were studied. The second experiment was conducted on 62 diabetic patients, with and without sympathetic skin response (SSR), to study proposed sole temperature normalization with respect to forehead temperature for clinical diagnosis.

RESULTS

In the first experiment, the temperature in each plantar subregion varied as a function of time. In the sole area, the highest temperature was noted in the arch region (29.3 +/- 0.9 degrees C). The toes had the lowest temperature value (26.2 +/- 1.2 degrees C) in all areas. Equilibrium was reached after 15 minutes for the mean plantar temperature (27.8 +/- 1.0 degrees C). In the second experiment, the diabetic patients without SSR had a slightly higher mean plantar temperature (27.6 +/- 1.8 degrees C) than those with SSR (26.8 +/- 2.2 degrees C), but the difference was not statistically significant (p > 0.05). The SSR-absent group (0.19) and the SSR-present group (0.24) had significant differences in their normalized temperatures as proposed (p < 0.05).

CONCLUSIONS

The mean temperature of the entire plantar area was found to be more stable than the individual subregions, serving as a more practical indicator for thermoregulatory functions. The study also found that the overall mean plantar temperature stabilized after 15 minutes, and, thus, this time was recommended for clinical thermographic measurements. The normalized temperature may have more useful application than the plantar absolute temperature, as exemplified by the better correlation in diabetic feet. The mean plantar temperature, the wait time to start measurement, and the proposed normalization are believed to play important roles in neuropathic foot disorders.