High-resolution Thermography Research Articles

Thermographic detection of heat radiation in caloric vestibular function tests

Since Bárány; caloric irrigations in the external ear canal have been used for unilateral stimulation of the peripheral vestibular system. However, the mechanism of heat transfer from the auditory canal to the vestibular organ is not completely known. From the physical point of view, three mechanisms may be discussed: heat conduction via the bone, convection via the middle ear gas, or radiation. Feldmann et al. (1991) singled out radiation as a very important factor in this regard. Using high-resolution thermography, we were able to "see" radiation almost directly in temporal bone experiments. Using the system of infrared thermovision specially adapted for close-up studies, the effect of calorization can be observed and documented in colored planar thermograms. Fresh temporal bone specimens had to be prepared so as to permit simultaneous observation of the tympanic membrane and the medial tympanic wall. Changes in temperature were readily visible during experimental caloric tests: turning blue indicated cooling and red indicated warming. In the caloric test with 44 degrees C or 30 degrees C water, changes in color of the eardrum appeared immediately. At the very same time, however, an area of the medial tympanic wall also changed color. This velocity of transfer cannot be attained by conduction or convection: heat radiation is the only possible explanation. This could only be demonstrated at the very onset of the reaction; subsequent thermograms became more and more diffuse. In this stage the heat transfer may also be effected by conduction and/or convection. Thermography demonstrates that radiation is a very important factor in heat transfer; at least in the initial phase of calorization.

Magnetization curves of amorphous video heads

Beneath a general electromagnetic characterization of the sandwich layers, measuring the magnetization curve of the assembled video-head allows to detect remanence and coercivity. The eddy current distributions have been also visualized by high resolution thermography. The described measuring methods allow conclusions for the optimization of many parameters of the investigated amorphous CoZrNb sandwich heads.

Use of High-speed, High-resolution Thermography to Evaluate the Tear Film Layer

To evaluate the tear film layer in patients with dry eye and in normal subjects by measuring the corneal temperature with infrared radiation thermography. One eye of each of 13 patients with dry eye and one eye of each of seven normal subjects were evaluated randomly. The corneal temperature was measured continuously with a recently improved infrared radiation thermography technique. We calculated the k value, which reflected the steepness of the corneal temperature change. The bigger the k value was, the more rapid was the decrease in corneal temperature, and this was directly related to increased evaporation. With normal blinking, the mean k value for patients with dry eye (5.6 +/- 2.9 per second) was significantly less than that in the control subjects (9.3 +/- 5.0 per second; P < .05). Keeping the eyes open after closing the eyes significantly decreased the k values compared with normal blinking in both groups (P < .05). Our findings demonstrate the usefulness of this method of measuring corneal temperature to evaluate the tear film layer. High-speed, high-resolution thermography detected subtle changes in corneal temperature with enhanced sensitivity and spatial and temporal resolution. We found that the mean k value, and therefore the rate of decline in corneal temperature in patients with dry eye, was significantly less than that in normal subjects. The k value may therefore reflect tear film layer stability. The measurement of the changes in the corneal temperature can thus give us valuable information on the tear film layer.

Thermal characterization of microsystems by means of high-resolution thermography

Thermal measurements on microsystems prove difficult due to small thermal masses and high thermal gradients, namely on thermally powered actuators. Compared with contacting thermometry or integration of thermally sensitive structures, thermography as a two-dimensional method may be a very powerful and exact method of measuring device temperatures and heat fields. The load capacity of interconnection lines, a bimetal micro actuator, and the development of a thermopneumatical actuator, are reported as examples for successful employment of infrared thermography in microtechnology.

High-resolution temperature measurement of void dynamics induced by electromigration in aluminum metallization

The local temperature of aluminum metallization is measured directly during electromigration. High resolution thermography is used to detect void dynamics induced by a dc current. In the vicinity of the growing area, infrared radiation pulses less than 0.5 s wide are observed concomitant with resistance pulses. Their amplitudes are found to correspond to a temperature increase of more than 200 °C, which locally exceeds the melting point of aluminum metallization. These pulses occur as a consequence of void movement. Healing of voids is discussed along with the results.

Dropwise Evaporative Cooling Of A Low Thermal Conductivity Solid

Insight on extinguishment of a solid fuel fire by sprinkler generated droplets is obtained by detailed modeling of a single droplet evaporative cooling on a hot low thermal conductivity solid. The assumption of constant and uniform temperature at the solid-liquid interface, which decouples the solid and the liquid modeling, cannot be applied to this case because strong local cooling of the solid requires the solutions of both regions (liquid and solid) to be coupled. The large thermal gradients observed at the edge of the droplet preclude the application of finite difference techniques for the integration of the transient conduction governing equation. A mixed technique that uses a control volume method for the liquid and a boundary element formulation for the solid is proposed. Both methods are briefly outlined and the computed predictions are validated with experimental measurements which encompass high resolution thermography of the solid surface subjected to evaporative cooling. Insight on the temperature distribution at the solid-liquid interface is obtained deduced from the model and the deviation from the constant and uniform temperature at the liquid-solid interface is assessed. The radial versus axial conduction in the liquid droplet is also quantified

High Resolution Thermography in Medicine

AbstractA high resolution medical thermal imaging system using an 8 element SPRITE detector is described. Image processing is by an Intellect 100 processor and is controlled by a DEC LSI 11/23 minicomputer. Image storage is with a 170 Mbyte winchester disc together with archival storage on 12 inch diameter optical discs having a capacity of 1 Gbyte per side.The system is currently being evaluated for use in physiology and medicine. Applications outlined include the potential of thermographic screening to identify genetic carriers in X-linked hypohidrotic ectodermal dysplasia (XED), detailed vascular perfusion studies in health and disease and the relationship between cutaneous blood flow, peripheral neurological function and skin surface temperature.

New developments in breast thermography. High spatial resolution.

Two design trends have become evident in the development of clinical thermo-graphic equipment—higher frame rates which meet the requirements for real-time presentation and novel color and isotherm techniques designed to increase the differential temperature capabilities of display systems. These developments, for the most part, have been accomplished at the expense of spatial resolution. Little has been reported on the characteristics of high spatial resolution thermography. With the rapid developments in detector technology, it has now become possible to retain the desired degree of temperature resolution at clinically acceptable frame rates while increasing spatial resolution. Such a system is presently being tested at the University of Texas M. D. Anderson Hospital and Tumor Institute and its performance compared with commercially developed thermographic units. The criteria for comparison are the diagnostic value of the thermograms and image quality as determined by the modulation transfer function. At the present time, the experimental thermograms indicate that high spatial resolution simplifies the recognition and classification of thermal patterns while decreasing the number of false-positive examinations. Information may also be derived concerning the heat transfer processes involved. The experimental scanner is not suited for routine clinical use and theoretical calculations concerning the development of an optimal clinical scanning device are presented.