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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↗

PubMed2005

A primer on radiometry.

Correctly measuring radiometric quantities and reporting radiometric data is essential in developing a more complete understanding of the requirements and polymerization kinetics of dental resin composites. Presented herein is an introduction to the fundamental concepts, quantities and units of radiometry. A brief discussion of photometry and how it differs from radiometry is also included. While the basic principles of radiometry are relatively straightforward, a great deal of attention must be paid to the details when performing radiometric measurements and reporting radiometric data. Meaningful radiometric measurements require very close attention to nomenclature and mathematical definitions. Radiometric, not photometric quantities should always be used, unless the goal is to report how the human eye perceives light.

Composite Resins↗

PubMed1972

Measurement of inflammation in man and animals by radiometry.

1. A radiometer is described, which is sensitive to infrared radiation in the range 0-25 mum, and which, after calibration with a black body standard can be used as a non-contact, fast reading thermometer.2. An example of acute joint inflammation in a patient with rheumatoid arthritis is described. The temperatures over the joint measured by radiometry, followed inflammatory changes in the joint effusion.3. Using rats, the method of measuring inflammation by radiometry was compared with measurements of increase in joint size. Changes measured by radiometry preceded changes shown by increase in joint size.4. The radiometer method was able to demonstrate the effect of an anti-inflammatory drug, given orally, against carrageenin inflammation.5. The procedure was found to be an accurate means of measuring inflammation and the anti-inflammatory effects of drugs. It was faster and less tedious than the other methods for the quantitative measurement of inflammation in man and animals.

Animals↗

PubMed2004

Quasistationary field of thermal emission and near-field radiometry.

We provide a theory of radiometry measurements of the quasistationary (near) field of thermal emission from a heated conducting medium. It explains why the Rytov effect, which essentially is a drastic growth of the thermal field energy near the medium surface, cannot be detected experimentally. However, we discovered a measurable near-field effect: the effective depth of formation of the received emission proves to be less than the skin-layer depth, depending on the size of the receiving antenna and its height above the surface. For such measurements highly effective antennas of a small aperture size are necessary. We developed and investigated a variety of microwave antennas whose parameters were fairly suitable for near-field radiometry. The measurements conducted with these antennas yielded experimental evidence of the fact that the quasistationary thermal field really exists. Near-field radiometry opens further opportunities for investigating media. In particular, we demonstrate here a technique for retrieval of the subsurface temperature profile in water with the help of near-field measurements.

Journal Article↗

PubMedDate not supplied

New 434 MHz interstitial hyperthermia system monitored by microwave radiometry: theoretical and experimental results.

A new complete microwave interstitial hyperthermia system monitored automatically by microwave radiometry and working at 434 MHz is described in this paper. This system, which includes a new radiometer with two internal temperature references, is detailed. All its characteristics for microwave heating and radiometry are presented. The new possibilities are shown through numerous experiments on acrylamide phantom and excised tissues, which have been carried out for different antennae implantation corresponding to the clinical situation. The clinic protocol, associate to the brachytherapy, imposes the use of semi-loop catheters. Coaxial antennae, inserted in these catheters, are not, therefore, positioned in a rectilinear manner but undergo a curve. So, models based on the FDTD formalism are developed to determine the theoretical power deposition. Owing to these models, the effects of this physical motive on radiation diagrams can be taken into account. The results of the power deposition are presented for two antennae. Thermal patterns can then be determined by the solution of the bioheat-transfer equation in the steady state. Also, the comparison of the results given by the new interstitial hyperthermia system with those obtained with the previous 915 MHz one shows an improvement of the thermal performances.

Electromagnetic Fields↗

PubMed2005

Microwave radiometry for continuous non-contact temperature measurements during microwave heating.

Temperature measurement during microwave heating in industrial and commercial processes can improve quality, throughput, and energy conservation. Conventional ways of measuring temperature inside a microwave oven cavity are costly, inconvenient, or unsuitable for high-volume industrial applications. In this paper, we describe the theory of microwave radiometry as applied to the measurement of temperature during microwave heating. By extending the theory of radiative transfer to the case of thermal microwave radiation inside a cavity, we show that the same characteristics which make a microwave cavity suitable for heating materials also assist in obtaining meaningful temperature data with microwave radiometry. We present experimental data from the heating of liquid and solid materials which confirm the essential features of the theory, and show agreement between this method and more conventional methods of +/-4 degrees C.

Computer Simulation↗

PubMed1987

Ultraviolet radiometry of clinical sources with a miniature multijunction thermopile.

Three versions of the Dexter 2M miniature multijunction thermopile were evaluated for the radiometry of clinical ultraviolet radiation (UVR) sources. The acceptance angle had been increased in two of these devices, and one also contained an additional ceramic heat sink under its receiver element. Measurements were made of their absolute sensitivity and linearity, and their response to various UVR sources was compared to that of Hilger Schwarz FT17 and FT32 vacuum compensated thermopiles. Both of the acceptance angle modifications yielded an angular response less than that of the wide-angle FT32 thermopile. The additional ceramic heat sink diminished, but did not eliminate, the initial surge in the 2M thermopile output voltage following exposure. Under constant irradiance, the 2M output voltage was stable after the initial surge had decayed, even without the additional heat sink. It was concluded that irradiance measurements should be made after the output voltage had stabilised. Any version of the 2M thermopile could be used for relative day-to-day monitoring of all UVR sources, and the version with the widest acceptance angle could be used for the absolute radiometry of certain extended sources.

Evaluation Studies as Topic↗

PubMed2001

The use of portable radiometry to assess Raynaud's phenomenon: a practical alternative to thermal imaging.

OBJECTIVES: To compare the performance of a portable radiometer with thermal imaging and to assess the potential for radiometry to provide a practical alternative for assessing vascular responsiveness in Raynaud's phenomenon (RP). METHODS: Subjects comprised 18 patients with diagnosed RP and 19 non-RP subjects. A thermal imager (Starsight) and a portable radiometer (Cyclops) measured digital temperature at baseline and the subsequent drop and rise in temperature following a cold challenge test. RESULTS: The intra-class correlations between the two instruments for all three measures exceeded 80%. The overall performance of each instrument was almost the same, the Starsight thermal imager correctly classifying 84% of subjects as RP or non-RP and the Cyclops portable radiometer correctly classifying 86% of subjects. The sensitivity of the thermal imager was 83%, compared with 89% for the portable radiometer; the specificity of both instruments was 84%. The positive and negative predictive values of the thermal imager were 83 and 84% respectively, and those for the portable radiometer were 84 and 89%. CONCLUSIONS: The two instruments performed equally well and the differences between them in their absolute measurements did not influence their ability to detect RP. Portable radiometry provides a practical, cheap, accurate and reliable alternative to thermal imaging and has the potential to be used in range of clinical and epidemiological settings.

Adolescent↗

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↗

PubMed1982

UVR radiometry of solar simulated radiation in experimental photocarcinogenesis studies.

The UVR radiometry of a long-term mouse photocarcinogenesis project is described. The methods used were (a) a phototherapy (UV-A) radiometer, (b) an electronic integrating dosimeter, (c) indirect spectroradiometry and (d) polysulphone and phenothiazine film badges for UV-B and UV-A respectively. The merits of the various methods are discussed. All but the phenothiazine film were considered to be satisfactory. The importance of reliable UVR radiometry is emphasized.

Animals↗

PubMed1993

Transurethral thermotherapy of the benign prostate hypertrophy controlled by radiometry.

Up to now control of the microwave heating of the prostate was only possible with rectal or urethral surface catheters. This problem has finally been solved with the help of the Prostcare apparatus (Bruker Spectrospin, Wissembourg, France) and radiometry: the prostate can be treated by the urethral or endorectal route with a 915-MHz generator and coaxial antennae, a unique device which allows us to measure real intraprostatic temperature, to regulate the microwave emission power and to eliminate classic surface controls. A sole antenna is used for the urethral catheter; it is introduced within the Foley-type probe and allows us to heat and measure the heat (radiometry). In this preliminary report, we present clinical results of the first 105 treated patients over 18 months by the transurethral route in a single 1-hour session: 7 have a protuberant median lobe and the treatment is without any effect; 76 patients can be analyzed and the Madsen score before treatment, at 3 months and at 6 months moves from 11.2 to 2.5 and 3.1, the maximum flow rate from 9.6 to 12.3 and 12.5 ml/s, the residue decreases from 102 to 68 and 53 ml. The session is well tolerated and patients mention that the effects are better than those of medical treatment. Hyperthermia is a simple method that will find its place between medical and surgical treatment once the numerous randomized studies have determined the most suitable therapeutic procedures.

Follow-Up Studies↗

PubMedDate not supplied

915 MHz microwave interstitial hyperthermia. Part I: Theoretical and experimental aspects with temperature control by multifrequency radiometry.

Microwave interstitial hyperthermia now plays an increasing part in the various hyperthermia techniques used in cancer treatment. This paper will present the design, construction and theoretical as well as experimental study of miniature coaxial antennas designed to heat tumours of various volumes and sizes. Monitoring temperature using multifrequency radiometry during hyperthermia stems naturally from the very design of these antennas. Experiments on phantoms, animals and patients in phase I clinical assessment have demonstrated that microwave interstitial hyperthermia can be achieved with temperature control and monitoring by microwave radiometry.

Animals↗

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↗

PubMed1985

UV radiometry in dermatology.

UV radiometry in photodermatology remains in an unsatisfactory state, which has been highlighted and, in some respects, worsened by improvements in UV detector technology. Complex, fundamental problems are involved, but matters have not been helped by a failure to recognize the clear distinction between those UV measurements which aim at accurate radiometry, and those which aim only at long-term consistency in a particular irradiation technique within a department.

Dermatology↗

PubMed1983

[Quantitative radiometry of [3H]androgens on silica gel plates with an aluminum layer].

A method for radiometry of [3H] androgens on silica gel aluminium-foil plates, without preliminary extraction of labeled steroids from the sorbent, was proposed. The presence of the plate with sorbent, with or without fluorophore, had no effect on quantitative radiometry. However, possible colour quenching effects should be taken into account. The method proposed allows to avoid losses of radioactive compounds at their quantitation.

Aluminum↗

PubMed1986

Detection of extravasation of antineoplastic drugs by microwave radiometry.

Microwave radiometry may be used as a non-invasive technique for subcutaneous thermal sensing. This technique was capable of demonstrating extravasation of small volumes of fluids, including the antineoplastic agent adriamycin, when these fluids were administered at room temperature in dogs. The rate of temperature drop upon extravasation was proportional to the flow rate. It is feasible that microwave radiometry may be useful as an alarm system to reduce serious complications which often accompany the extravasation of antineoplastic drugs.

Animals↗