Infrared Imaging Technique Research Articles

Future non-invasive imaging to detect vascular plaque instability and subclinical non-obstructive atherosclerosis.

Atherosclerosis underlies the major causes of death in the Western World. Our main goal is to detect early changes of atherosclerosis and to identify subjects at highest cardiovascular risk that may aid in the development of prevention approaches and better management that will decrease cardiovascular morbidity and mortality. The new methods that are of interest include the advanced vascular ultrasound methods, the infra red and near infra red imaging techniques, the EndoPat device that reflects peripheral arterial tone, the electron beam computed tomography, the magnetic resonance imaging, and the molecular imaging techniques. In this review we will focus on the future of advanced imaging techniques that are being developed to detect early (pre-clinical) development of atherosclerosis.

Identification of Carbon Black in Military Textiles Using Infrared Imaging Techniques

The carbon black has been used in military fabrics to comply with the color requirements and infrared radiation lessening criteria. Currently, military industries don’t distinguish between fabrics with carbon black fibers or with carbon black into dyes or prints. The latter initially allows us to comply with the color specifications in the visible and infrared, but fabrics are degraded with use losing that initial capacity. The inclusion of carbon black in the fiber gets that the fabric doesn’t degrade with the wear, washed and dried, ensuring the accomplishment of the specifications all the time. The use of infrared imaging will allow us to define a method to discriminate those textiles with carbon black in their fibers from those which are dyed or printed.

Infrared Imaging and Spatiotemporal Radiation Properties of a Turbulent Nonpremixed Jet Flame and Plume

Radiation transfer from turbulent nonpremixed jet flames and plumes is important in many applications such as energy-efficient combustion systems, temperature sensitive pollutant control, and detection, control, and suppression of accidental fires. Combined spatial and temporal correlations of scalar values such as temperature and species concentrations affect the emitted radiation intensity. Spatiotemporal correlations and radiation intensity measurements downstream of the reacting parts of flames (plumes) have received limited attention. Motivated by this, planar time-dependent narrowband radiation intensity measurements are acquired of a turbulent nonpremixed flame and its plume using an infrared camera. Temporally and spatially correlated instantaneous realizations of local scalars and path integrated intensity values are calculated using a stochastic time and space series analysis, a narrowband radiation model, and the radiative transfer equation. The time-dependent infrared images reveal intermittent, low intensity regions in the plume characteristic of buoyancy-dominated transport. High radiation intensity structures are observed in the flame characteristic of momentum dominated flow and vorticity driven mixing. Normalized intensity fluctuations are nearly constant in the flame region, but increase by up to a factor of three in the plume. Normalized temporal correlations, power spectral density functions, and spatial correlations of the intensity are independent of the spatial location throughout both the flame and the plume. Spatial correlations of the radiation intensity exhibit approximately linear decay to half an integral length scale followed by an exponential decrement. The radiation intensity fluctuations remain spatially correlated up to separation distances two times larger than the integral length scale. Space–time cross correlations of the intensity fluctuations are measured for the first time and are shown to be more isotropic in comparison to the product of the spatial and temporal correlations. This suggests that a correction factor should be applied to the space–time correlation model in future stochastic calculations to account for the anisotropy. The infrared imaging technique, illustrated in this paper, is promising to be a useful qualitative and quantitative nonintrusive technique for studying both reacting and nonreacting flows.

In vitro and in vivo theophylline release from cellulose/chondroitin sulfate hydrogels

In vitro and in vivo release of the theophylline, loaded in mixed polysaccharidic cellulose/chondroitin sulfate (C/CS) hydrogels has been evaluated. The C/CS hydrogels in various mixing ratios obtained by a crosslinking technique were supplementary characterized by swelling studies in a pH 2.2 acidic solution at 37°C, simulating the gastrointestinal medium, as in vivo theophylline delivery was done by oral administration. The hydrogels loading degree with theophylline was evaluated by near infrared chemical imaging (NIR-CI) technique and confirmed also by FT-IR spectroscopy. Based on PLS-DA (partial least squares-discriminate analysis) prediction, the drug loading was found up to 92.5%. The in vitro release profiles of theophylline from C/CS hydrogels showed that an increase of chondroitin sulfate leads to a decreased theophylline percent released, increased half release time and time to reach maximum percent released. During in vivo test, the raw theophylline was rapidly, absorbed, distributed, and eliminated. Comparatively with raw drug administration, the t1/2 and AUC0–72 value were 4 times higher for theophylline loaded into 50/50 C/CS hydrogel. A good in vitro–in vivo correlation was found. A retarded release, controlled by CS content can be achieved by using mixed hydrogels as carriers.

The Use of Thermal Infra-Red Imaging to Detect Delayed Onset Muscle Soreness

Delayed onset muscle soreness (DOMS), also known as exercise induced muscle damage (EIMD), is commonly experienced in individuals who have been physically inactive for prolonged periods of time, and begin with an unexpected bout of exercise1-4, but can also occur in athletes who exercise beyond their normal limits of training5. The symptoms associated with this painful phenomenon can range from slight muscle tenderness, to severe debilitating pain1,3,5. The intensity of these symptoms and the related discomfort increases within the first 24 hours following the termination of the exercise, and peaks between 24 to 72 hours post exercise1,3. For this reason, DOMS is one of the most common recurrent forms of sports injury that can affect an individual’s performance, and become intimidating for many1,4. For the last 3 decades, the DOMS phenomenon has gained a considerable amount of interest amongst researchers and specialists in exercise physiology, sports, and rehabilitation fields6. There has been a variety of published studies investigating this painful occurrence in regards to its underlying mechanisms, treatment interventions, and preventive strategies1-5,7-12. However, it is evident from the literature that DOMS is not an easy pathology to quantify, as there is a wide amount of variability between the measurement tools and methods used to quantify this condition6. It is obvious that no agreement has been made on one best evaluation measure for DOMS, which makes it difficult to verify whether a specific intervention really helps in decreasing the symptoms associated with this type of soreness or not. Thus, DOMS can be seen as somewhat ambiguous, because many studies depend on measuring soreness using a visual analog scale (VAS)10,13-15, which is a subjective rather than an objective measure. Even though needle biopsies of the muscle, and blood levels of myofibre proteins might be considered a gold standard to some6, large variations in some of these blood proteins have been documented 6,16, in addition to the high risks sometimes associated with invasive techniques. Therefore, in the current investigation, we tested a thermal infra-red (IR) imaging technique of the skin above the exercised muscle to detect the associated muscle soreness. Infra-red thermography has been used, and found to be successful in detecting different types of diseases and infections since the 1950’s17. But surprisingly, near to nothing has been done on DOMS and changes in skin temperature. The main purpose of this investigation was to examine changes in DOMS using this safe and non-invasive technique.

The Use of Thermal Infra-Red Imaging to Detect Delayed Onset Muscle Soreness

Delayed onset muscle soreness (DOMS), also known as exercise induced muscle damage (EIMD), is commonly experienced in individuals who have been physically inactive for prolonged periods of time, and begin with an unexpected bout of exercise, but can also occur in athletes who exercise beyond their normal limits of training. The symptoms associated with this painful phenomenon can range from slight muscle tenderness, to severe debilitating pain. The intensity of these symptoms and the related discomfort increases within the first 24 hours following the termination of the exercise, and peaks between 24 to 72 hours post exercise. For this reason, DOMS is one of the most common recurrent forms of sports injury that can affect an individual's performance, and become intimidating for many. For the last 3 decades, the DOMS phenomenon has gained a considerable amount of interest amongst researchers and specialists in exercise physiology, sports, and rehabilitation fields. There has been a variety of published studies investigating this painful occurrence in regards to its underlying mechanisms, treatment interventions, and preventive strategies. However, it is evident from the literature that DOMS is not an easy pathology to quantify, as there is a wide amount of variability between the measurement tools and methods used to quantify this condition. It is obvious that no agreement has been made on one best evaluation measure for DOMS, which makes it difficult to verify whether a specific intervention really helps in decreasing the symptoms associated with this type of soreness or not. Thus, DOMS can be seen as somewhat ambiguous, because many studies depend on measuring soreness using a visual analog scale (VAS), which is a subjective rather than an objective measure. Even though needle biopsies of the muscle, and blood levels of myofibre proteins might be considered a gold standard to some, large variations in some of these blood proteins have been documented, in addition to the high risks sometimes associated with invasive techniques. Therefore, in the current investigation, we tested a thermal infra-red (IR) imaging technique of the skin above the exercised muscle to detect the associated muscle soreness. Infra-red thermography has been used, and found to be successful in detecting different types of diseases and infections since the 1950's. But surprisingly, near to nothing has been done on DOMS and changes in skin temperature. The main purpose of this investigation was to examine changes in DOMS using this safe and non-invasive technique.

Prediction of contact surface temperature between rough sliding bodies – numerical analysis and experiments

PurposeThe paper's aim is to predict numerically the contact temperatures between two rough sliding bodies and to compare with the experimental results.Design/methodology/approachAn elastic contact algorithm is used to analyze the normal contact between two nominally smooth surfaces. The algorithm evaluates real contact area using digitized roughness data and the corresponding contact pressure distribution. Using finite element method a steady state 3D temperature distribution at the interface between the sliding bodies is obtained. Using infrared (IR) imaging technique, experiments were carried out to measure the contact temperature distribution between rough rubbing bodies with a systematic variation of surface roughness and operating variables.FindingsContact temperature distributions over a wide range of normal load, sliding velocity and surface roughness have been obtained. It was seen that the maximum contact temperature expectedly increases with surface roughness (Sa values), normal load and sliding velocity. The results also indicate that the “hot spots” are located exactly at the positions where the contact pressures are extremely high. Temperatures can be seen to fall drastically at areas where no asperity contacts were established. The temperature contours at different depths were also plotted and it was observed that the temperatures fall away from the actual contact zone and relatively high temperatures persist at the “hot spot” zones much below the contact surface. Finally it is encouraging to find a good correlation between the numerical and experimental results and this indicates the strength of the present analysis.Research limitations/implicationsExperimental accuracy can be improved by using a thermal imaging camera that measures emissivity in situ and uses it to find the contact temperature. The spatial resolution and the response time of the camera also need to be improved. This can improve the correlation between numerical and experimental results.Practical implicationsOne of the major factors attributed to the failure of sliding components is the frictional heating and the resulting flash temperatures at the sliding interface. However, it is not easy to measure such temperatures owing to the inherent difficulties in accessing the contact zone. Besides, thermal imaging techniques can be applied only with such tribo‐pairs where at least one of the contacting materials is transparent to IR radiation. In practice, such cases are a rarity. However, the good correlation observed between the numerical and experimental results in this work would give the practicing engineer a confidence to apply the numerical model directly and calculate contact temperatures for any tribo‐material pairs that are generally seen around.Originality/valueA good correlation between the numerical and experimental results gives credence to the fact that the numerical model can be used to predict contact temperatures between any sliding tribo‐pairs.

The Assessment of Melanoma Risk Using the Dynamic Infrared Imaging Technique

Melanoma is the deadliest form of skin cancer. Each year more than 53,600 people learn that they have melanoma, and around 8700 people die from melanoma in the United States. Early detection is the key to improving survival in patients with malignant melanoma. We developed a thermal (infrared) imaging system that allows accurate measurements of small temperature differences on the skin surface with the aim to diagnose malignant pigmented skin lesions at an early stage of the disease. The imaging method we developed relies on active infrared imaging and a multimodal image analysis strategy, including involuntary body/limb motion correction and interactive lesion segmentation for detecting malignant lesions. The imaging system described in the paper was tested in a pilot patient study in which patients who possess a pigmented lesion with a clinical indication for biopsy were selected to participate. The lesion and the surrounding healthy skin were cooled by air at 15 °C for 30–60 s, and the thermal recovery was imaged with the infrared camera after the removal of this cooling stress. We found that the benign lesions have a thermal recovery similar to normal skin, whereas the thermal recovery of the melanoma lesion is different. It was observed that a malignant skin lesion has a higher temperature than healthy skin during the thermal recovery process (up to 2.2 °C higher for a Clark’s level II melanoma). The present study shows the feasibility of dynamic thermal imaging in distinguishing malignant pigmented lesions from benign, look-alike pigmented lesions.

Investigation into the Merits of Infrared Imaging in the Investigation of Tattoos Postmortem

Infrared imaging has a history of use in the forensic examination of artwork and documents and is investigated here for its wider use in the detection of tattoos on the human body postmortem. Infrared photographic and reflectographic techniques were tested on 18 living individuals, displaying a total of 30 tattoos. It was observed that neither age, sex, age of the tattoo, nor, most significantly, skin color affected the ability to image the tattoos using infrared imaging techniques. Second, a piglet carcass was tattooed and the impact of the decomposition process on the visibility of the tattoos assessed. Changes were recorded for 17 days and decomposition included partial mummification and skin discoloration. Crucially, the discoloration was recorded as greatly affecting the image quality using conventional photography, but was insignificant to the infrared recording of these tattoos. It was concluded that infrared reflectography was beneficial in the investigation into tattoos postmortem.

In-Vivo Detection of Skin Cancer Using the Dynamic Infrared Imaging Technique

In-Vivo Detection of Skin Cancer Using the Dynamic Infrared Imaging Technique

Effects of upstream ramp on the performance of film cooling

Described in this paper is an experimental study on a concept for enhancing the film cooling performance by placing an upstream ramp in front of a row of film cooling holes. Parameters studied include upstream ramp angle (8.5°, 15°, and 24°) and blowing ratio M (0.3, 0.4, 0.6, 0.9, and 1.4). Detailed local film cooling effectiveness and heat transfer coefficient are measured using the infrared imaging technique. The results indicate that film cooling characteristics in the region downstream of the film cooling holes are sensitive to the combination of ramp angle (height) and blowing ratio. In general, a large ramp angle with a high blowing ratio leads to more effective film protection. Transport phenomena in the region link closely to the interaction between the coolant injection and the separated flow behind the ramp.

Laser microperforated biodegradable microbial polyhydroxyalkanoate substrates for tissue repair strategies: an infrared microspectroscopy study

Flexible and biodegradable film substrates prepared by solvent casting from poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) solutions in chloroform were microperforated by ultraviolet laser ablation and subsequently characterized using infrared (IR) microspectroscopy and imaging techniques and scanning electron microscopy (SEM). Both transmission synchrotron IR microspectroscopy and attenuated total reflectance microspectroscopy measurements demonstrate variations in the polymer at the ablated pore rims, including evidence for changes in chemical structure and crystallinity. SEM results on microperforated PHBHV substrates after cell culture demonstrated that the physical and chemical changes observed in the biomaterial did not hinder cell migration through the pores.

A Review on Synthesis and Characterization of Lead Zirconate Titanate Nanofibers through Electrospinning

This paper reviews our previous work on synthesis and characterization of ferroelectric lead zircornate titanate nanofibers through electrospinning. It addresses the synthetic procedure and mechanism, process and material characterization using viscometery, thermal analysis, scanning electron microscopy/energy dispersion spectrometery, Auger electron spectrometery, scanning probe microscopy, x-ray diffraction, Fourier-transform infra-red spectrometery, Raman micro-spectrometery and piezo-response imaging techniques. It also looks into numerical analysis on the electrostatic field distribution during the electrospinning and piezo-response imaging processes.

Dispersion modeling approach for quantification of methane emission rates from natural gas fugitive leaks detected by infrared imaging technique

Recently, infrared optical imaging has been applied in the oil and gas industry as a method to detect potential leaks in pipelines, components and equipment. The EPA suggested that this impending technique is considered as a smart gas LDAR (leak detection, monitoring and repair) for its rapid recognition of leaks, accuracy and robustness. In addition, compared to the conventional method using Total Vapor Analyzer (TVA) or gas sniffer, it has several other advantages, such as the ability to perform real-time scanning and remote sensing, ability to provide area measurement instead of point measurement, and provide an image of the gas which is not visible to naked eye. However, there is still some limitation in the application of optical imaging techniques; it does not give any measurement of gas emissions rates or concentrations of the leaking gas. Infrared cameras can recognize a target gas and distinguish the gas from its surrounding up to a certain concentration, namely the minimum detectable concentration. The value of the minimum detectable concentration depends on the camera design, environmental conditions and surface characteristics when the measurement is taken. This paper proposed a methodology to predict gas emissions rates from the size of the dispersed gas plume or cloud to the minimum detectable concentration. The gas emissions rate is predicted from the downwind distance and the height of the cloud at the minimum detectable concentration for different meteorological conditions. Gas release and dispersion from leaks in natural gas pipeline systems is simulated, and the results are presented.

Local heat transfer distribution on a flat plate impinged by a compressible round air jet

An experimental investigation is carried out to study the local heat transfer distribution on a flat plate orthogonally impinged by a single round compressible impinging jet using thin metal foil technique. The surface temperature of the impingement plate is measured using thermal infrared imaging technique. A circular pipe of diameter 10 mm is used to obtain Mach numbers of 0.2, 0.4, 0.6, 0.8 and 1 for the corresponding Reynolds numbers of 44 000, 88 000, 133 000, 176 000 and 221 000 respectively. The circular pipes of diameters 6 mm, 7.3 mm, 10 mm and 15 mm are used to obtain Mach numbers of 1, 0.83, 0.6 and 0.4 respectively for a constant Reynolds number of 133 000. The jet-to-plate distance ( z/ d) is varied from 1 to 12 nozzle diameters. The adiabatic wall temperature is used as a reference temperature for the calculation of the local Nusselt number. It is found that the heat transfer rate increases with increase in Mach number (Reynolds number) for all nozzle-to-plate distances at all radial locations. The stagnation point Nusselt number is maximum at z/ d = 6 for incompressible flow and at z/ d = 8 for compressible flow. The substantial increment in average Nusselt number is observed as Mach number is increased from 0.2 to 0.4 as compared to the increment in average Nusselt number for Mach number increase from 0.8 to 1.0. Recovery factor variation with radial location is almost independent of the Reynolds number and the Mach number but varies with jet-to-plate distance. Recovery factor more than unity at stagnation point is reported for larger jet-to-plate distances ( z/ d > 8).

Possibilities of using modern infrared imaging devices for measuring the temperature of the lasing regions of solid-state lasers pumped with high-power laser diodes

The modern infrared imaging technique is applied to studies of the temperature fields and heat loads of Er:YAG laser crystals under conditions of optical pumping of these crystals with high-power (20 W) radiation from diode arrays with fiber outputs. It is shown that state-of-the-art infrared imagers operating in the range 8–14 μm can be efficiently used to monitor the near-surface temperatures in the lasing regions of solid-state lasers under high-power diode pumping. The possibilities of modern infrared imagers for evaluating the degree of heating of the lasing region in a laser crystal, the temperature distribution in this region, and the efficiency of operation of cooling systems and for preliminarily rejecting active laser elements have been demonstrated.

Evidence for complete and partial surface renewal at an air‐water interface

A wind‐wave flume is used to determine the extent to which the thermal boundary layer (TBL) at a wind‐forced air‐water interface is completely renewed from below. We measure skin temperature, Tskin, radiometrically, temperature immediately below the TBL, Tsubskin, using a temperature profiler, and net heat flux using the gradient flux technique. The Tskin probability density function, p(Tskin), and surface renewal time scale, τ, were measured using passive and active infrared imaging techniques, respectively. We find that the mean percentile rank of Tsubskin in p(Tskin) is 99.90, implying that complete surface renewal occurs. This result suggests an alternative to radiometric measurement of Tskin through the simple combination of an infrared camera and an in situ temperature sensor. Comparison of the temperature difference across the TBL to the expected cooling implies that a significant portion of events only partially renew the TBL. This result should impact efforts to improve air‐sea transfer models.

Amphiphilic Cross-Linked Networks Produced from the Vulcanization of Nanodomains within Thin Films of Poly(N-vinylpyrrolidinone)-b-Poly(isoprene)

Diblock copolymers of poly(N-vinylpyrrolidinone) (PNVP) and poly(isoprene) (PIp) were employed as building blocks for the construction of complex cross-linked networks that present surfaces having amphiphilic character, imparted by covalent trapping of compositionally heterogeneous phase-separated morphologies. The kinetics for the homopolymerization of N-vinylpyrrolidinone by reversible addition-fragmentation chain transfer (RAFT) techniques was studied, and the initially obtained PNVP-based macro-RAFT agents were then extended to PNVP-b-PIp block copolymers. Therefore, the PNVP chain length was held constant at a number-averaged degree of polymerization of 120, while the PIp chain length was varied to afford a series of three PNVP120-b-PIpx block copolymers (where x=710, 53, and 25). These materials were then cross-linked individually using sulfur monochloride, to produce complex amphiphilic networks. The nanoscopically resolved topographies of these films were analyzed using atomic force microscopy, and their compositional heterogeneities were probed by X-ray photoelectron spectroscopy and internal reflectance infrared imaging techniques. Additionally, the surfaces were analyzed to determine the extent of surface reorganization under aqueous conditions.

Infrared imaging of AP/HTPB laminate propellant flames

The combustion of ammonium perchlorate (AP), hydroxyl-terminated polybutadiene (HTPB) two-dimensional laminate propellants is investigated using simultaneous infrared (IR) and ultraviolet (UV) emission imaging at 1–50 atm. The IR (3300–3900 nm) measurements sense flame presence nominally via HCl rovibrational excitation and the UV (310 nm) measurements via OH electronic excitation, although continuum emission is also present. The following findings are made. (1) The new IR results generally confirm the flame-structure regime map (split vs merged flames) obtained previously from UV observations for both pure and oxygenated fuel-binders. Here “merged” refers to lateral merging of the two diffusion flame branches (one for each fuel–AP interface) as pressure and fuel-layer thickness are reduced. (2) A new finding (not seen previously in the UV) is that for pure binder systems at relatively low pressures ( < 15 atm ) , IR imaging clearly shows two stream-wise distinct diffusion flames, which are possibly the primary diffusion flame (PDF) and final diffusion flame (FDF) structures postulated in the BDP model. (3) As pressure increases the PDF and FDF flames observed for pure binder merge stream-wise and become indistinguishable. (4) Oxygenated fuel-binder (75:25 fine-AP/HTPB-binder) laminates do not show distinct PDF and FDF flames. (5) The IR imaging technique improves on the UV in terms of surface definition because of the differences in IR versus UV absorption/emission properties of fuel-rich gaseous species near the burning surface: oxygenated binder surfaces that appear protruding in UV in the split-flame regime are less so in IR. (6) Computational results using just the AP-premixed and final diffusion flames capture the flame-surface structure regime map qualitatively but not quantitatively, further underscoring the importance of the primary diffusion flame.

Computerized Image Analysis

Computerized Image Analysis