Sizing the Depth and Width of Narrow Cracks in Real Parts by Laser-Spot Lock-In Thermography

We present a complete characterization of the width and depth of a very narrow fatigue crack developed in an Al-alloy dog bone plate using laser-spot lock-in thermography. Unlike visible micrographs, which show many surface scratches, the thermographic image clearly identifies the presence of a single crack about 1.5 mm long. Once detected, we focus a modulated laser beam close to the crack and we record the temperature amplitude. By fitting the numerical model to the temperature profile across the crack, we obtain both the width and depth simultaneously, at the location of the laser spot. Repeating the process for different positions of the laser spot along the crack length, we obtain the distribution of the crack width and depth. We show that the crack has an almost constant depth (0.7 mm) and width (1.5 µm) along 0.7 mm and features a fast reduction in both quantities until the crack vanishes. The results prove the ability of laser-spot lock-in thermography to fully characterize quantitatively narrow cracks, even below 1 µm.

Evaluation of digital thermography imaging to assess and monitor treatment of police working dogs with naturally occurring hip osteoarthritis

Background In dogs, thermal imaging has been documented only recently, but a growing interest in this modality has led to studies using thermography to assess pathologies in the canine hip, stifle, elbow, intervertebral disc, and bone neoplasia. This study aimed to evaluate the use of digital thermography in assessing and evaluating treatment response in dogs with hip osteoarthritis (OA) and comparing its results with an objective measure and two clinical metrology instruments. In an experimental, randomized, double-blinded study, one hundred hip joints of fifty police working dogs with bilateral hip OA were evaluated. A dorsoventral and lateral thermographic image were obtained on days 0, 8, 15, 30, 90, and 180. Mean and maximal temperatures were determined. Additionally, the animal’s weight-bearing distribution and radiographic examination of the hip joint (extended legs ventrodorsal view) were performed. Copies of the Canine Brief Pain Inventory (CBPI) and Canine Orthopaedic Index (COI) were obtained. Results were analyzed by ANOVA, followed by an LSD post-hoc test, and correlations were assessed with Spearman correlation coefficient, with p < 0.05. Results Values recorded on the lateral view were higher than those on the dorsoventral view. No differences or correlations were found between Orthopedic Foundation for Animals hip grades and temperature. Digital thermographic images showed a weak significant correlation with weight-bearing evaluations (r = 0.13, p < 0.01) and different clinical metrology instruments scores (r = − 0.25, p < 0.01 for pain severity score, and r = − 0.21, p = 0.04 for gait). It also correlated with radiographic findings, specifically the circumferential femoral head osteophyte and caudolateral curvilinear osteophyte. Conclusion To our knowledge, this is the first study presenting the digital thermography assessment of Police working dogs submitted to treatment for hip OA. Digital thermography, mainly based on a lateral view evaluation, showed a weak significant correlation with stance analysis and clinical metrology instruments scores.

Thermographic visualization of facial vasoconstriction is associated with 30-day all-cause mortality in medical patients; prospective observational two-site cohort study

Introduction: Quick and reliable assessment of acute patients is required for accurate triage. The temperature gradient between core and peripheral temperature could possibly instantly provide information on circulatory status. Methods: Adult medical patients, who did not receive supplementary oxygen, attending two emergency departments, had a thermographic image taken on arrival. The association between 30-day mortality and gradients was tested using logistic regression. Results: 726 patients were studied, median age was 64 years and 14 (1.9%) died within 30 days. There was a significant association between mortality and temperature gradient, comparable to vital signs, age, and clinical intuition. Conclusion: Temperature gradient between nose and eye had an acceptable discriminatory power for 30-day all-cause mortality.

Correlation between skin temperature in the lower limbs and biochemical marker, performance data, and clinical recovery scales

The aim of this study was to evaluate the correlation between tools commonly used in the detection of physiological changes, such as clinical complaints, a biochemical marker of muscle injury, and performance data during official matches, with infrared thermography, which has been commonly used in the possible tracking of musculoskeletal injuries in athletes. Twenty-two athletes from a professional soccer club (age 27.7 ± 3.93 years; BMI 24.35 ± 1.80 kg/cm2) were followed during the season of a national championship, totaling 19 matches with an interval of 7 days between matches. At each match, the athletes used a Global Positioning System (GPS) device to collect performance data. Forty-eight hours after each match, every athlete’s perception of recovery, fatigue, and pain was documented. Blood was collected for creatine kinase (CK) analysis, and infrared thermography was applied. Only athletes who presented pain above 4 in either limb were included for thermographic analysis. Each thermographic image was divided into 14 regions of interest. For statistical analysis, we included only the images that showed differences ≥ 1° C. Data normality was verified by the Kolmogorov-Smirnov test with Dallal-Wilkinson-Lilliefors correction. We used the Pearson correlation coefficient to verify the correlation between infrared thermography and the biochemical marker, performance data, and clinical recovery scales. No correlation was observed between mean skin temperature and blood CK levels, pain level, perception of recovery, and fatigue perception (r <0.2, p>0.05). Thus, infrared thermography did not correlate with CK level, pain, fatigue perception, or recovery, nor with performance variables within the field.

Cálculo do perfil de temperatura em um modelo tridimensional da mama para análise paramétrica da influência da posição e do tamanho de um tumor maligno

<span class="fontstyle0">Thermography is a technique that is being proposed as an auxiliary tool in breast cancer screening. It gains importance, especially due to the increased incidence of this cancer in the Brazilian female population. These images are also used for the validation of three-dimensional numerical simulations. The production of a more realistic and personalized breast model would allow a more accurate estimate of the sensitivity of thermography as a technique capable of early detection of breast cancer. This work proposes the development of a methodology to produce a custom three-dimensional breast geometry from the manually extracted curves of the thermograms contained in UFPE Thermographic Image Database. With this geometry, parametric analyzes were performed, seeking to understand the influence of tumor depth and size on the calculated temperature profile.</span> <br /><br />

Design of a Didactical Activity for the Analysis of Uncertainties in Thermography through the Use of Robust Statistics as Teacher-Oriented Approach

The thermography as a methodology to quantitative data acquisition is not usually addressed in the degrees of university programs. The present manuscript proposes a novel approach for the acquisition of advanced competences in engineering courses associated with the use of thermographic images via free/open-source software solutions. This strategy is established from a research based on the statistical and three-dimensional visualization techniques over thermographic imagery to improve the interpretation and comprehension of the different sources of error affecting the measurements and, thereby, the conclusions and analysis arising from them. The novelty is focused on the detection of non-normalities in thermographic images, which is illustrates in the experimental section. Additionally, the specific workflow for the generation of learning material related with this aim is raised for asynchronous and e-learning programs. These virtual materials can be easily deployed in an institutional learning management system, allowing the students to work with the models by means of free/open-source solutions easily. Subsequently, the present approach will give new tools to improve the application of professional techniques, will improve the students’ critical sense to know how to interpret the uncertainties in thermography using a single thermographic image, therefore they will be better prepared to face future challenges with more critical thinking.

Evaluating Patterns of Building Envelope Air Leakage with Infrared Thermography

The next-generation performance-based building energy codes are focusing on minimizing building envelope air leakage. The quantification of air leakage in buildings is typically performed with a blower door test. However, this test does not provide information about the locations of air leakage. The aim of this study is to demonstrate a method involving qualitative and quantitative components that can be used to characterize locations of air leakage with infrared thermography. Since air leakage can have a significant impact on building energy consumption in cold climates, like in Canada, this approach can quickly inform where air barrier discontinuities occurred during construction or where to selectively target air sealing efforts in existing buildings. The observations from this study are presented, based on a thermographic image analysis during a depressurized blower door test at various pressures, in an attempt to quantify the relative rates of air leakage. The results from the investigation showed that infrared thermography (IRT) was able to discern locations and infer relative ratios of air leakage. The qualitative analysis showed that areas of air leakage are more evident under higher pressure difference. The quantitative approach showed that a minimum of 25 Pa pressure difference was required to detect the air leakage in the vicinity of the window frame, as the surface temperature decreased rapidly (almost 60% of the indoor surface/outdoor air temperature difference) at this pressure. A temperature index was defined to prioritize the areas of air leakage for retrofitting purposes. Furthermore, a thermal image subtraction method was used to determine the characteristics of the cracks based on thermal patterns. Finally, the practical implication of this study, for building developers, home inspectors, property mangers, and homeowners, is the early detection of air leakage for both existing and newly constructed buildings which could result in energy and cost savings.

Assessment of Disease Activity by Infrared Thermography in Patients with Rheumatoid Arthritis: A Comparative Cross-Sectional Study of Thermographic, Clinical and Ultrasound Assessments

OBJECTIVES: To compare RA activity evaluation by thermal imaging with a camera adjustable to cellphones, standard clinical examination and ultrasound.MATERIALS AND METHODS: Monocentric study with 3 independent evaluations of RA activity: 1) tender (TJC) and swollen joints count (SJC) of wrists, MCP and PIP; 2) Ultrasound (US) examination with mode B and Power Doppler (PDUS); 3) thermographic assessment using infrared thermal cellphone camera FLIR One®. Thermal images analysis with (a) software detecting 10 regions of interest (ROI) corresponding to the studied joints and (b) by color reading (arthritis yes/no). For each ROI, temperature difference measurement “ΔT-joint” (ΔTj) compared to the ipsilateral forearm (reference area) and comparison of ΔTj to a) TJC and SJC; b) US synovitis in B mode or c) PDUS grade (0,1,2,3); d) synovitis in visual detection on thermographic image. T-tests and ANOVA were performed.RESULTS: 53 patients (43 women) with a mean (SD) age of 61.6 (12.3) years, totaling 921 examined joints. Mean disease duration was 17.6 (11.1) years. RA status was 81% ACPA+, 58% erosive, mean DAS28 score was 4.0 (1.6).Mean ΔTj was higher in tender (p<0.001), swollen (p=0.066) joints and in US synovitis in B mode (p=0.021). Mean ΔTj was not associated with PDUS category (p-ANOVA=0.072). Synovitis detected with thermal image reading was associated with PDUS grade 3 (p<0.001). CONCLUSION: Our results did not show the ability of thermal imaging to assess RA activity in small joints. However, our results are encouraging as temperature variation were observed in inflammatory joints.

Thermography in persistent postoperative pain after knee surgery

Aims and Objectives: Background: Postoperative persistent pain occurs in approximately 10% of surgically treated patients. It incapacitates and reduces quality of life in those affected. The aetiology is poorly understood, predictive factors are currently unknown, diagnosis and therapy are difficult. Objectives: To evaluate the benefit of dermal thermography in the diagnosis and therapy of persistent postoperative pain. Study design: retrospective, Level of evidence IV Materials and Methods: A single surgeon performed highly standardized ACL reconstructions, arthroscopies and total endoprotheses of the knee. Patients were seen six weeks postoperative for clinical and thermographic evaluation. Regions of interest were defined for the affected knee, a control region defined for the contralateral knee. The thermographic image was used to pinpoint a site for subcutaneous local anaesthesia. The clinical evaluation was then repeated. Results: Patients in total (n=133), arthroscopy (n=21), total endoprothesis (n=42), ACL (n=50). If the temperature difference (TD) between the site of pathology and the average ipsilateral knee temperature was negative, pathology was classified as hypothermic (n=19), otherwise hyperthermic (n=94). Arthroscopically treated patients showed a TD of 0,88 ± 0,39 °C in hyperthermic (n=12) and -0,811 ± 0,623 °C in hypothermic (n=9) knees. Prosthetically treated patients showed a TD of 1,29 ± 0,51 °C in hyperthermic (n=37) and -0,88 ± 0,33 °C in hypothermic (n=5) knees. ACL treated patients showed a TD of 1,20 ± 0,48 °C in hyperthermic (n=45) and -0,62 ± 0,41 °C in hypothermic (n=5) knees. The difference in temperature between the site of pathology and the average temperature of the ipsilateral knee was significant for all subgroups: arthroscopy-hypothermic p < 0,001, arthroscopy-hypothermic p < 0,005; endoprothesis-hyperthermic p < 0,001, endoprothesis-hypothermic p < 0,004; ACL-hyperthermic p < 0,001, ACL-hypothermic p < 0,027. In contrast to the hyperthermic groups (for all p < 0,001), there was no significant difference between the site of pathology and the contralateral control region in the hypothermic groups. All patients reported a reduction of pain and better mobility after subcutaneous infiltration with Scandicain 2% at the thermographically defined site of pathology. Conclusion: Thermography is useful to pinpoint sites of pathology in persistent postoperative pain. Two types of thermal abnormality could be identified at the site of pathology: hypo- and hyperthermic. Local anaesthesia at the site of pathology resulted in pain reduction and improved mobility. Further studies are necessary to understand the postoperative thermal changes in order to devise a suitable therapy.