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At least 19 recordsLinked to original sources
PubMed1992

Microwave radiometry in biomedicine: a reappraisal.

Nearly 20 years ago the first papers appeared on biomedical applications of microwave radiometry, and many other papers have since appeared. Yet, despite its unique capabilities, microwave radiometry has so far received only limited acceptance by the medical community, and little commercial success. The chief reasons, we suggest, are the shallow depth of sensing and the difficulty of extracting imaging information from radiometry signals emitted by electrically heterogeneous media. A secondary factor has been the difficulty of validating many proposed clinical applications for the method--in particular, cancer detection. We suggest that microwave radiometry is a viable method of thermal sensing, but its successful applications are likely to be quite different than those that were originally conceived for the technique.

Extravasation of Diagnostic and Therapeutic Materi↗
PubMedDate not supplied

[Ultrahigh-frequency radiometry and endoscopy in the diagnosis of maxillary diseases].

The potential of SHF-radiometry was investigated in the diagnosis of maxillary inflammation. Altogether 90 patients and 30 controls underwent routine infrared thermography and SHF-radiometry. Normal thermal distribution in the maxillary sinuses was featured by its picture in normal subjects. SHF-radiometry proved more informative in bilateral localization of the inflammation foci, in sluggish processes in the maxillary sinuses, allowed more significant follow-up of the thermogenic activity of the maxillary deep tissues. SHF-radiometry findings were verified at maxillary endoscopy. The results correlated in 77.9% of the cases. The method can be introduced to make early diagnosis of maxillary inflammation, in mass health check-ups.

Adult↗
PubMed1992

Microwave radiometry in living tissue: what does it measure?

The sensitivity of microwave radiometry for detecting subcutaneous targets was studied both experimentally and theoretically. The radiometer used a dielectric loaded rectangular waveguide antenna in contact with a lossy dielectric medium. A cylindrical target with dielectric properties and/or temperature different from that of the surrounding medium was located beneath this surface. For most of the studies, the target and the surrounding medium were maintained at constant, but unequal, temperatures (i.e., heat conduction effects were insignificant). The received radiometric signal was calculated as the location and dielectric properties of the target were varied. Finally, the radiometer signal was calculated for the situation with the target maintained at constant temperature but with the surrounding medium modeled by the bioheat equation. Experimental studies were performed using a radiometer operating at 4.7 GHz. The target was a thin walled tube through which a temperature controlled liquid was circulated, located in a temperature controlled fluid tank. The results indicate that microwave radiometry (as used in this study) responds to the temperature averaged over the field pattern of the antenna with very strong weighting of regions near the surface. A simple quasi-static analysis provides a good indication of the sensitivity of the technique for detecting cylindrical targets whose dielectric properties are different from those of the surrounding medium. A simple estimate of thermal conduction around the target suggest that thermal effects greatly increase the apparent size of the target.

Electromagnetic Phenomena↗
PubMedDate not supplied

[Local radiometry in the diagnosis of postoperative pulmonary complications].

34 patients in the first 5 days after surgery have been examined by local radiometry technique, using 125I-fibrinogen. Significant differences in the accumulation of marked fibrinogen have been revealed in patients with and without postoperative lung complications. The analysis of the data obtained made it possible to reveal signs characteristic of patients at high risk of pulmonary complications already on the second day postoperatively. Local pulmonary radiometry is recommended as an informative diagnostic technique for early identification of postoperative pulmonary complications of thrombotic genesis.

Adolescent↗
PubMed1989

[Local radiometry of tumors of the breast].

The authors propose a radionuclide method of diagnosis of breast tumors based on focal radiometry of 99mTc-pertechnetate accumulated in them after injection. Radiometry is done with a scanner with a pulse counter. The ratio of pulse counts accumulated in a tumor, to this indicator on the contralateral side makes it possible to determine a tumor type. This method is of diagnostic importance for tumors with a diameter less than 2 cm, their individual sections and also for lymph nodes.

Breast Neoplasms↗
PubMed1992

Determination of optical properties of turbid media using pulsed photothermal radiometry.

Pulsed photothermal radiometry (PPTR) measures blackbody radiation emitted by a sample after absorption of an optical pulse. Three techniques for obtaining the absorption coefficient of absorbing-only, semi-infinite samples are examined and shown to give comparable results. An analytic theory for the time dependence of the PPTR signal in semi-infinite scattering and absorbing media has been derived and tested in a series of controlled gel phantoms. This theory, based on the diffusion approximation of the radiative transport equation, is shown to model the time course of the detected signal accurately. Furthermore, when the incident fluence is known, the theory can be used in a non-linear, two-parameter fitting algorithm to determine the absorption and reduced scattering coefficients of a turbid sample with an accuracy of 10-15% for transport albedos ranging from 0.42-0.88.

Algorithms↗
PubMedDate not supplied

Spatial resolution measurements for passive microwave radiometry using a tissue-equivalent phantom.

A tissue-equivalent "hot" line source phantom is described for assessing spatial resolution in passive microwave radiometry systems. LSFs were measured for two rectangular waveguide antennas connected to a 4.7-GHz radiometer. The normalized LSFs and corresponding modulation transfer functions were found to be independent of line source temperature, but dependent upon antenna size, orientation, and line source depth.

Biophysical Phenomena↗
PubMed1991

[The prevention method of inadvertent irradiation during laser stone fragmentation by the fiber-optic radiometry analysis].

To minimize urothelial tissue injuries by inadvertent laser irradiation during the laser stone fragmentation, we developed a novel fiber-optic analysis system which is able to distinguish the urothelial tissues from urinary stones. The reflection mode of the pulsed photo-thermal radiometry (PPTR) was employed for non-destructive tissue characterization. We developed the first fiber-optic PPTR system using chalcogenide infrared glass fibers as a transmission line. As excitation light sources for the samples, three different lasers were used in vitro and compared to select the proper excitation laser which is able to distinguish wet urinary stones from urothelial tissues. The e-folding decay time of the PPTR waveform, by which the samples are characterized, was measured as an index. The ultraviolet argon (UV Ar) laser had the best discriminative faculty. Using UV Ar laser, the e-folding decay time of calcium oxalate stones, uric acid stones and the ureter, was 239 +/- 57 ms, 33 +/- 4 ms, and 102 +/- 24 ms (p less than 0.001), respectively. The new analysis system which was composed of the fiber-optic PPTR analyzer using UV Ar laser excitation together with a thin-fiber endoscope was applied to measure the e-folding decay time of PPTR waveform of urinary stones and canine ureters in vivo general anesthesia. The e-folding decay time of calcium oxalate stones, uric acid stones and the ureter was 153 +/- 15 ms, 26 +/- 3 ms and 246 +/- 31 ms, respectively. The canine ureter was clearly differentiable from urinary stones by the measurement of the e-folding decay time of PPTR waveform.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Non-invasive thermometry with multi-frequency microwave radiometry.

The present status of the development of a non-invasive thermometer based on microwave radiometry at our laboratory is reported. We have developed a model fitting technique combined with a Monte Carlo technique to retrieve temperature-depth profiles from multi (4-6)-frequency-band microwave radiometric data along with confidence intervals (2-sigma) of tissue temperatures as a function of depth. In order to make the radiometric technique compatible with the heating, brightness temperatures are measured through a 1 cm thick water bolus. Results of phantom experiments are presented to demonstrate the above capabilities of the method. Numerical simulation studies have shown that 2-sigma intervals would be 1.0 K or less over a 0-4 cm range and 1.4 K at 5 cm from the surface with using a six-band, 1-5 GHz radiometer having brightness temperature resolution of 0.03 K (3 s integration time). The six-band instrument is currently being assembled at our laboratory.

Body Temperature↗
PubMed1976

[Study of different states of iodine metabolism in rats by means of whole-body radiometry].

The authors present the principal concepts necessary for the use of the method of radiometry of the whole body in studying the iodine metabolism in vivo in the intact and thyroidectomized rats and also in experimental hyperthyroidism resulting from TTH or thyroidin administration. The iodine metabolism indices in euthyroidism and athyroidism in rats proved to be adequate to the corresponding curves of the iodine metabolism indices in healthy persons and those suffering from myxedema. Experimental hyperthyroidism in rats, similarly to hyperthyroidism in man, was characterized by an increase in tissue metabolism of the hormonal iodine. However, it was accompanied by an accelerated clearance of the organism from an excess of thyroid hormones; due to this it could not serve as an adequate model of thyrotoxicosis in man.

Animals↗
PubMed1976

[Application of infrared radiometry on the eye (author's transl)].

The non-contact determination of temperature by infrared radiometry allows the focal measuring of the surface temperature of the radiation source. In 119 patients the surface temperature in the middle of the cornea was measured by this method. The average temperatures were 33.50 degrees C (+/-0.91) in men and 33.74 degrees C (+/-0.91) in women. Further clinical testing is suggested first in diseases of the oculo-orbital region and secondly by means of a connected recorder to study the dynamic temperature reaction under the influence of different parameters.

Adolescent↗
PubMed1989

Infra-red surface thermography. Evaluation of a new radiometry instrument for measuring skin temperature over joints.

A study is reported of the evaluation of a new portable, light-weight, infrared thermometer, for the measurement of the skin temperature over joints. A high degree of reproducibility was observed, but no increase in heat was found over selected rheumatoid joints. The instrument will prove useful in detecting temperature changes in disease states where the changes are considerable, and where the ambient temperature can be strictly controlled.

Body Temperature↗
PubMed1989

Radiometry and laser safety standards.

The application of occupational limits (ELs) in the outdoor laser environment requires an understanding of the radiometric methods required to evaluate field exposures with respect to the ELs. The limiting aperture required to adequately specify the EL must always be kept in mind. Since all exposure limits are defined as a function of time, electro-optical detectors and instrumentation must have an adequate temporal response and have an absence of saturation effects. As a field-expedient method thermally sensitive paper can also be employed to estimate the output radiant exposure of pulsed lasers. For evaluating potential ocular hazards in the retinal hazard spectral region (400 to 1400 nm), one should employ a 7-mm aperture. For evaluating potential hazards to the skin and the cornea, a 1-mm limiting aperture is justified. Although the impact of the 1-mm limiting aperture is to reduce the limiting power which is considered safe--the accessible emission limit for Class 1 laser products, it nevertheless is justified for field exposure of the eye, as has been shown in recent experimental studies of corneal injury.

Accident Prevention↗
PubMed1975

The Denver universal microspectroradiometer (DUM). II. Computer configuration and modular programming for radiometry.

This paper describes and discusses for microscopists and spectroscopists the choice of computer equipment and the design of programs used in the Denver Universal Microspectroradiometer (DUM). This instrument is an accurate computerized photon-counting microspectrophotometer, microspectrofluorimeter and microrefractometer. The computer is used to control the operation of the system, to acquire radiometric data of various kinds, and to reduce, analyse and output the data in a readily usable form. Since the radiometer was designed to carry out many kinds of measurements in a variety of micro- and macroscopic specimens, and since different methods of microscopy or spectroscopy have to be combined in various ways fro the study of any one specimen, no single master-program could fulfill efficiently all foreseeable requirements. Therefore, the programming developed is interactive, modular, hierarchical and hybrid. Modular interactive programming makes it possible for almost any kind of main program, applicable to almost any kind of measurement, to be assembled quickly from a collection of hierarchical subroutines. Main programs are short and composed mainly of Fortran statements calling subroutines; subroutines, in turn, automatically call other subroutines over many levels. The subroutines are independently written and optimized for maximum operational efficiency in the computer system used, or for maximum ease of transfer to other systems. This approach to programming enables someone unfamiliar with computer languages to operate the radiometric system from the console of the CRT terminal. The writing of new main programs, by linking groups of existing subroutines, requires only a minimum acquaintance with Fortran; only the writing and revision of subroutines requires programming experience. Differences and similarities in the method of computer operation between the present system and other computerized radiometers are briefly discussed.

Computers↗