Showing papers on "Thermography published in 1980"

Thermography as an indicator of blood perfusion.

Abstract: Skin temperatures recorded by the scanning infrared camera are the resultant balance of the thermal transport within the tissues and the transport to the environment. In medical thermography, the thermal image is obtained in a controlled environment usually with temperature at approximately 2OOC. The rate of thermal energy flow from the skin to the environment is consequently the result of the convection and radiation modes. The evaporation rate is normally low under equilibrium conditions in such an environment and thus is only a secondor higher-order effect. It is very important that the clinic environment be carefully controlled. This control includes an assurance that the clinic is isothermal (k0.2OC) and that the airflow over the patient is uniform and steady. With control of the environment, the skin temperature may then be utilized to estimate the physiological activity influencing the surface temperature. On convex surfaces of the body that do not receive thermal radiation from other parts of the skin, the thermal image demonstrates a range of temperatures. On the abdomen, thorax and back, the normal range observed will be from about 25OC to a maximum of 36OC. The higher temperature represents the skin superficial to veins that are involved in active transport of blood. It is well known that collateral venous networks provide for blood returning to the vena cava to flow in either the deep veins, the superficial system, or both. The superficial veins course just below the skin and superficial to the subcutaneous fat layer. The blood in the active veins will represent an average temperature of the tissues drained. Thus the skin temperatures associated with these venous patterns provide important information for the assessment of the physiological state. Factors affecting skin at a distance from these veins are blood perfusion, tissue thermal conductivity, and metabolic heat generation. It is important to the understanding of the meaning of skin temperature patterns that the relative role of each of these variables be known. It is unfortunate that much of the medical literature has totally misinterpreted the skin temperatures as being the direct result of a high temperature source (a tumor) buried within the tissue. The following analysis demonstrates conclusively that the blood perfusion associated with metabolic activity dominates the effect of metabolic heat generation. Draper and Boag'** indicate that the increase in temperature of the skin noted with breast cancer is due primarily to increased blood flow. However, they proceeded to utilize a pure conduction model neglecting the effects of blood perfusion in computation of the skin temperature patterns. They discount the work of Law~on.~ In fact, the measurement of temperature of blood flowing in arteries and veins during surgery is extremely difficult. The temperatures of arterial blood reported by Lawson

Microwave thermography in the detection of breast cancer

Abstract: Microwave thermography, a method of sensing subcutaneous temperatures, was used in a breast cancer detection study of about 5,000 female patients. The data were taken at wavelengths of 9.1 and 23 cm. Microwave thermography at 23 cm has true-positive and true-negative detection rates of 0.8 and 0.6, respectively, comparable to those of infrared thermography (0.7) and inferior to those of xeromammography (0.9). However, a potential advantage results if microwave and infrared thermography are used together for screening, and if mammography is used only for follow-up on those patients who were positive on either the microwave or the infrared thermograms. It is then possible to obtain true-positive and true-negative detection rates of 0.9 and 0.9, respectively, while only half the number of patients need be subjected to x-rays.

Neonatal skin temperature distribution using infra-red colour thermography.

Abstract: 1. Infra-red Colour Thermography was used to visualize skin temperatures over seven neonates nursed in a modified temperature controlled incubator. 2. Temperature distributions were recorded on cine film which was analysed to evaluate mean skin temperatures; these were subsequently compared with values obtained from multiple, weighted measurements from a thermocouple thermometer. In all cases, there was agreement to within +/- 0 . 6 degrees C. 3. Thermograms in thermo-neutral conditions (approximately 32 degrees C) showed a temperature distribution with the warmest skin overlying the central hot ‘core’ and temperatures falling towards the extremities. Temperature patterns in a cooler environment (approximately 28 degrees C) showed features due to the conductive or thermogenic nature of the structures underlying the skin. 4. Multiple skin temperature recordings made at two environmental temperatures were obtained from a further twelve infants. 5. Linear regression of skin temperature against rectal--environmental difference, performed for each of the measured sites, showed that the upper arm and, to a lesser extent, the upper thigh temperatures represented the mean value most closely. The upper abdomen and head were both warmer and less responsive to environmental change than the mean skin temperature. These findings were supported by the thermographic observations.

Microwave thermography of normal and cancerous breast tissue

Abstract: In this report we review the relevant physical principles and instrumentation of centimeter wavelength microwave radiometry. We have called this technique microwave thermography in analogy with the well-known infrared method. We present results of a clinical study of breast cancer detection at 1.3 GHz (23-cm wavelength) and 3.3 GHz (9-cm), and we describe the performance of our new 6-GHz (5-cm) radiometer. Some of this material has been presented elsewherel-’’ and is included here for purposes of review.

Thermography for estimating near-surface soil moisture under developing crop canopies

Abstract: Previous investigations of thermal infrared techniques using remote sensors (thermography) for estimating soil water content have been limited primarily to bare soil. Ground-based and aircraft investigations were conducted to evaluate the potential for extending the thermography approach to developing crop canopies. A significant exponential relationship was found between the volumetric soil water content in the 0-4 cm soil layer and the diurnal difference between surface soil temperature measured at 0230 and 1330 LST (satellite overpass times of NASA's Heat Capacity Mapping Mission - HCMM). Surface soil temperatures were estimated using minimum air temperature, percent cover of the canopy and remote measurements of canopy temperature. Results of the investigation demonstrated that thermography can potentially be used to estimate soil temperature and soil moisture throughout a complete growing season for a number of different crops and soils.

Thermography: Testing of the thermal insulation and airtightness of buildings

Abstract: This publication, which mainly refers to measurements made in the laboratory, proposes rules for the interpretation of thermograms. The invstigations described in this report were mainly made in situ, i.e. in completed buildings. They deal in greater detail with the parameters concerned, measuring conditions, the interpretation procedure, etc, and give practical examples of thermography and of systematic defects in the thermal insulation and airtightness of buildings.

Passive Visible To Infrared Transducer For Dynamic Infrared Image Simulation

Abstract: A passive visible to infrared image transducer is described which allows practical simulation of high resolution dynamic infrared imagery for the first time. A theoretical performance analysis is presented which indicates an MTF of 50% at 5 cycles/mm is achievable with a time response of less than 20 msec and a required input power of less than 2 mw/cm2 per simulated degree ΔT. Experimental results on working devices are reported which match theoretical predictions. Successful simulation of high speed real-world infrared imagery is described. Suggestions for future work are presented which should further enhance resolution and dynamic range.

Rosette Scan Infrared Sensor

Abstract: This paper describes the design analysis and results of performance test of a rosette scan infrared sensor which can be used as a thermal imager as well as a radiation seeker for search and tracking. The fundamental properties of a sensor are discussed, and the relationship between sensor parameters has been made clear. The effect of bandwidth on the noise equivalent irradiance(NEI) is also investigated by using a simplified model. On the basis of these analyses, the sensor which responds in the 3 to 5 μm spectral band has been designed, fabricated and tested. It has been verified that the minimum NEI over the total field of view could be realized by optimizing the bandwidth at the center of the field of view. The ability as a thermal imager has also been demonstrated by displaying rosette-scanned thermal images on a CRT monitor, and the detection capability of a target on a display has been evaluated by measuring the minimum detectable temperature difference(MDTD).

Comparison of Doppler sonography and plate thermography for detection of carotid artery stenosis.

Abstract: Foils coated with specific cholesterol esters indicate differences in temperature by changes in color. When these foils are placed on the skin, the skin temperature measured is related to the perfusion provided by the vessels supplying this area of the skin. A group of 300 patients were examined simultaneously with plate thermography and directional Doppler sonography in order to detect obstruction or occlusions of the carotid artery. Abnormalities were found in 42 patients. In 31, the positive findings obtained by the 2 methods were in agreement. In 8 only plate thermography gave a positive result, and in 3 only Doppler sonography yielded a relevant finding. Plate thermography as a method for the detection of a stenosis or an occlusion of the carotid artery is suggested as useful for an initial screening method.

Microwave Radiothermometry (9GHz) Applied To Breast Cancer

Abstract: Radiothermometric investigations have been carried out on breast cancer patients and on patients with tumors of various localizations and histologic types (liver,thyrold,...) (55 cases), by means of a high sensitivity hyperfrequency radiometer operating at 9GHz.The findings were analyzed as follow: (a) comparison between microwave thermal mapping and infrared thermography; (b) correlations with various morphologic and thermal parameters (depth and size oftumor thermal conductivity, vascularization and x-ray structures of tissues). Microwave radiometry seems to be able to provide significant information on meta-bolism and thermal conditions of subcutaneous tumor tissue, especially under those clinical situations where infrared thermography does not work.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Clinical Applications Of Microwave Thermography

Abstract: More than a hundred cases of thyroidal, osteoarticular, facial or intracranial pathologies have been explored with microwave thermography at 9, 30 and 68 GHz. We have been able to detect deep lesions such as those of femoral head or lumbar spine, or cerebral tumors, with the help of this technology.

Liquid crystal thermography

Abstract: PURPOSE:To form the simplified thermography without using electronic scanning and optical-mechanical scanning by combining a pyroelectric element and a liquid crystal element and applying AC bias between the specified elements of the abovemented elements. CONSTITUTION:The layers composed of electrodes 2, pyroelectric material 1 and respectively independent multiple electrode/reflecting plates 3 are laminated on the infrared light incident side to form the pyroelectric element. On the other hand, glass 6, liquid crystal electrodes 7 and multiple liquid crystals 4 partitioned by liquid crystal pool frames 5 are laminated on the visible light incident side to form the liquid crystal element. The abovementioned electrode/reflecting plates 3 and liquid crystals 4 are so disposed as to mutually oppose to each other and one end of an AC source 40 is connected to the electrodes 2 and the other end to the electrodes 7 through a variable resistance 41 to form the liquid crystal thermography. By using the abovementioned thermography, the infrared light from a constant temperature plate and the specimen is alternately radiated to the pyroelectric element surface by way of a rotary chopper tuned to the AC source and the liquid crystal element surface is observed, whereby the high and low of the temperature of the specimen is measured.

Using liquid dielectrics to obtain spatial thermal distributions.

Abstract: A liquid dielectric has been used to determine thermal distributions for several clinically useful waveguide applicators as used in microwave hyperthermia. The system uses a saline/ethanol filled compartment placed within a temperature controlled water bath set to 37.5 degrees C. Thermal distributions are taken with a thermistor probe placed perpendicular to the electric field. In this way longitudinal and transverse cross sections of the heat deposition due to microwave interaction with the liquid dielectric can be elicited. A similar arrangement was carried out using phantom material and an infrared camera as described by Guy. Comparison of the central axis data and cross-sectional thermal distribution of these two systems shows good agreement.

Cholesteric plate thermography: the state of the art

Abstract: The science of photography, whose beginnings are traced to the early 18OOs, the discovery of a fourth state of matter in 1888,’ and the development of microencapsulation in the mid-1950s2 have recently been combined to produce what the news media somehow has called a “space-age” breakthrough, cholesteric plate thermography. The first widely reported use of sheets of encapsulated cholesterics for thermal medical investigations was published in 1974 by Gautherie, Quenneville, and Gros.’ Since that time there have been intensive development activities to produce thermographic plate cholesterics for the medical community. The major emphasis in this development has been in the quality control of the six major steps of cholesteric thermographic plate manufacture. These basic steps are: (1) formulation, (2) encapsulation, (3) coating preparation, (4) coating, (5) plate assembly, and (6) final calibration. To expand on some of these basic steps, consider first, the formulation of the mixed cholesteric ester phase. It has been the experience of the industry that single and binary components are of little use in thermographic systems. In order to have maximum control of the thermal event and the intensity of the reflected light response, multicomponent systems are necessary. A ternary system is the minimum number of components considered to be useful; however, four, five, and six components afford the best control of a system. FIGURE 1 is a slice through six-dimensional component space. The major components are a t the apices of the triangle and the three minor components are held constant. The thin black curves, a t 5°C intervals, depict the temperature of the isotherm observed between the second-order reflection and the red reflection (also described as the onset of red). The dashed curves represent the differences in degree, Celsius between the initial isotherm and the isotherm observed between the green and blue reflection. This is usually referred to as the thermal window. The compositions most frequently used for thermographic purposes are located along the 3OC dashed line bounded by the 25” and 4OoC black curves. The formulated cholesterics are encapsulated by using the process outlined in FIGURE 2. The encapsulated cholesterics, after the addition of proper binders and coating modifiers, are coated onto a clear substrate of polyester film. Multiple coating applications are usually necessary for optimum results. The coating operation is finished by the application of a black back-coating. This final coating absorbs the nonreflected wavelengths and provide the necessary contrast for observing the wavelengths reflected by the cholesterics. The coated material is assembled in a suitable frame. The completed thermographic plate is processed through its last step called “final calibration.” Thermal checks of the cholesteric preparations are constantly made throughout the entire

Characteristics of active and passive 2-D holographic scanner imaging systems for the middle infrared

Abstract: Holographic scanners are suggested for imaging in the 8–13-μm spectral region. Advantages in refrigeration and reliability are pointed out. The narrow linewidth of received irradiance may limit passive systems to applications such as thermography, where multispectral imaging should be a useful diagnostic tool. Active systems, which do not suffer from this range limitation, offer inherent advantages with regard to resolution improvement via background discrimination and also with respect to countermeasures.

Microwave Thermography ; The Modeling of Probes ; An Approach Toward Thermal Pattern Recognition

Abstract: Recent developments about Microwave Radiometry concern the Reception of the thermal signals emitted by subcutaneous human tissues (Microwave Thermography). Several equipments have been built and clinical examinations carried out, in order to detect tumors, for example. Now, it is necessary to study the characteristics of the electromagnetic coupling between probe and tissues, and to explain the thermal patterns.

Infrared Techniques for the Evaluation of Silicon Carbide Heat-Exchanger Tubing

Abstract: The potential application of infrared techniques to detect flaws and measure heat transport in silicon carbide heat-exchanger tubing is discussed. Axial heat-flow patterns were monitored with a commercially available infrared camera. Computer modeling was used to help establish the relationship between temperature distributions and the various thermal parameters. The experimental data and computer-modeling predictions were in fair agreement. These tests indicated that thermography may be a useful nondestructive-evaluation technique for rapid assessment of thermal-heat-transport properties in silicon carbide heat-exchanger tubing.

Errors In Passive Infrared Imaging Systems Due To Reflected Ambient Flux

Abstract: Passive infrared imaging systems produce a signal in which the amplitude at a particular spot is related to the radiance of the corresponding spot in the scene viewed. The differences in signal levels in different areas of the image is usually interpreted in terms of radiance temperature differences in the scene viewed, and may be converted to true radiance temperatures if the scene includes an object whose radiance temperature is known.The radiance temperatures are usually converted to true temperatures by correcting for the emittance of objects in the scene. This would be correct in the absence of reflected ambient flux. However, for scenes at ambient temperatures, ambient flux is always present in significant amounts. Temperature errors due to reflected ambient flux are discussed from a theoretical standpoint, and a procedure for experimentally evaluating the ambient flux is suggested.IntroductionInfrared thermography produces a monochromatic image in which the brightness of an area in the cathode-ray tube image is related to the apparent radiance of the corresponding area in the scene viewed. These apparent radiances are frequently interpreted in terms of the radiance temperature of the area in the scene, or more commonly, in terms of the temperature differences between different areas in the scene, which can be converted into true temperatures, or temperature differences, if the emittances of the materials viewed are known. Such interpretation is subject to errors, which are frequently over­ looked. The principal errors are due to atmospheric absorptance and the reflected radiance of the areas viewed. Only the latter error will be discussed in this paper.The problem is easier to deal with when the measurements are made in an enclosed area, with walls at a reasonably uniform temperature. These conditions apply both to infrared thermography in an enclosed area, and optical pyrometer temperature measurements inside a furnace, but this discussion will be confined to infrared thermography in a room.Blackbody radiatorsFirst, we will define a blackbody radiator and discuss its properties. A blackbody is a surface having the properties of (1) absorbing all incident radiant energy; (2) emitting the maximum possible concentration of spectral exitance (or radiance) for any body at its temperature at all wavelengths. The basic physical laws of radiation were derived for blackbody radiators. They are expressed as the Planck equation, which relates the spectral exitance (or radiance) of a blackbody to its temperature and the wavelength of the emitted radiation; the Stefan-Boltzmann equation, which relates the spectrally total exitance (or radiance) of a blackbody to its temperature; Lambert's law, which in essence states that the radiance of a blackbody radiator is independent of direction; and Kirchhoff's law, which states that, for a body in thermal equilibrium, heated and cooled by radiation only, the radiant energy absorbed is equal to that emitted.Blackbody cavitiesNo true blackbody surface exists in nature, but a completely enclosed cavity with opaque walls at a uniform temperature is a true blackbody. If a small aperture is made in the wall of the cavity, the blackbody radiation can be observed with only a very slight degradation of the quality of the blackbody. Since the opaque walls of the cavity are at a uniform constant temperature, they are in thermal equilibrium, and reemit all incident radiant energy they absorb, and since the walls are opaque, all incident radiant energy that is not absorbed is reflected. Hence the emittance and reflectance of the walls sum to one, and the exitance of any area on the wall is equal to the irradiance on that area, regardless of the emittance at that point.

Applications Of Infrared Thermography In The Analysis Of Induced Surface Currents Due To Incident Electromagnetic (EM) Radiation On Complex Shapes

Abstract: Thermography has been available for some time as an aid in the determination of temperature differentials. Burton, et al, have demonstrated that thermographic techniques may be used qualitatively to detect induced surface currents resulting from impinging Electromagnetic (EM) waves on particular shapes. The surface currents are detectable because of the energy deposited on the object in the form of I2R heating. A knowledge of the induced surface currents is invaluable to the study of radar cross section reduction and Electromagnetic Pulse (EMP) absorption. Therefore, a method is presented which provides a method of determining the temperature distribution on a complex shape subjected to microwave radiation. Thermographic detectors are either energy detectors (thermocouples) or photon detectors (semiconductors). A model is developed for each type which describes the infrared emission detection associated with a complex shape.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Analysis of solar collector array systems using thermography

Abstract: The use of thermography to analyze large solar collector array systems under dynamic operating conditions is discussed. The research has focused on thermographic techniques and equipment to determine temperature distributions, flow patterns, and air blockages in solar collectors. The results of this extensive study, covering many sites and types of collectors, illustrate the capabilities of infrared analysis as an analysis tool and operation and maintenance procedure when applied to large arrays. Thermographic analysis of most collector systems showed temperature distributions that indicated balanced flow patterns with both the thermographs and the hand-held unit. In three significant cases, blocked or broken collector arrays, which previously had gone undetected, were discovered. Using this analysis, validation studies of large computer codes could examine collector arrays for flow patterns or blockages that could cause disagreement between actual and predicted performance. Initial operation and balancing of large systems could be accomplished without complicated sensor systems not needed for normal operations. Maintenance personnel could quickly check their systems without climbing onto the roof and without complicated sensor systems.

Thermographic examination of circulatory function - in hands and feet, by applying thermographic substrate to cooled skin

Abstract: The use of a thermographic substrate with a sensitivity range pref. having a central value of 21 degrees C, for diagnosis of human hand and foot function is new. A portion of the body to be tested is cooled with a liq. medium at 21 plus-or-minus 0.5 degrees C, then immediately the cooled portion examined thermographically by heat-conducting contact. Pref. the substrate has sensitivity range 19-25 degrees C. The method is used to detect changes in blood circulation. It has fewer material requirements than infrared thermography, is reproducible, reliable, simple and quick.