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At least 55 records · Page 3Linked to original sources
PubMedDate not supplied

A new method for thermal dosimetry in microwave hyperthermia using microwave radiometry for temperature control.

Microwave radiometry has been used during the last few years in some clinical centres (Lille, Freiburg, Strasbourg, Brussels) for the non-invasive control of temperature during microwave hyperthermia. The principal objective of this paper is to present an atraumatic thermal dosimetry system based on numerical simulations of hyperthermia and radiometric temperature measurements for TEM propagation. To gauge the feasibility and performance of the method, a one-dimensional model in a homogeneous medium is considered, neglecting the curvature of the tissue layer. The good correlation between the theoretical and experimental values obtained allowed the likely thermal profile on the probe axis to be computed using the dielectric and thermal properties of the medium and measurement of the radiometric and cutaneous temperatures.

Computer Simulation↗
PubMedDate not supplied

Non-invasive microwave multifrequency radiometry used in microwave hyperthermia for bidimensional reconstruction of temperature patterns.

Microwave radiometry, used routinely since 1984 for non-invasive temperature measurements during hyperthermia sessions for superficial tumours treatment has proven its efficiency for temperature control. From radiometric temperature measurements in two frequency ranges (around 1 and 3 GHz) and superficial (or cutaneous) temperature measurements achieved during hyperthermia sessions, a numerical method to obtain the two-dimensional thermal profile has been developed and implemented. This method is based on hyperthermia simulation from the bioheat equation, the absorbed microwave power calculation in the medium taking into account the radiative diagram of the applicator, and the calculation of radiometric temperatures. From these experimental measurements (radiometric and superficial temperatures, heating power, dielectric and thermal characteristics), a program to determine the bidimensional distribution of temperature during the hyperthermia session has been developed, tested and used during and after clinical treatments.

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↗
PubMed1988

[Analysis of internal carotid-posterior communicating artery aneurysms with difficulty in clipping: with special reference to radiometry].

Although internal carotid-posterior communicating artery (ICPC) aneurysms seem to be one of the easiest to be operated on, some are known difficult to handle and could not be successfully clipped even with all sorts of preparations. It is, therefore, essential to analyze ICPC aneurysms with difficulty in clipping. Out of 106 cases with ICPC aneurysms admitted to Kyoto University Hospital since May 1977, 83 cases have been registered in this study to the exclusion of either non-operated cases or giant aneurysm cases. Cases with difficulty in clipping procedure are selected and classified depending on its causes, which were judged from operation records as well as operative photographs. Angiograms have been checked to discuss whether possible causes of difficulty in clipping could have been suspected preoperatively. Radiometry were also performed in the following items; distance between the anterior clinoid process (ACP) and proximal side of the aneurysmal neck (W) in AP view, distance of proximal side of the neck from ACP (D) and its height (H) from the baseline between the ACP and posterior clinoid process in lateral view. Causes of difficulty in clipping procedure can be grouped as follows: a) ventrally directed dome of the aneurysm (9 cases), b) incision of the plica petroclinoidea anterior (PPA) or removal of the anterior clinoid process (ACP) to identify proximal side of the neck (7 cases: b group), c) saucer-shaped dome with no apparent neck, d) branches of the internal carotid artery from dome.(ABSTRACT TRUNCATED AT 250 WORDS)

Carotid Artery Diseases↗
PubMed1998

Design of a four-crystal monochromator beamline for radiometry at BESSY II.

A four-crystal monochromator beamline will be part of the radiometry laboratory that the Physikalisch-Technische Bundesanstalt will install at the new storage ring BESSY II. The most important design criteria for the beamline are the tunability of the photon energy in a wide spectral range from 1.75 to 10 keV, the high spectral purity of the radiation, as well as the good reproducibility of the absolute photon flux.

Journal Article↗
PubMed1998

High-accuracy detector calibration in the 3-1500 eV spectral range at the PTB radiometry laboratory.

State-of-the-art detector calibration in the UV/VUV and soft X-ray spectral ranges at the Physikalisch-Technische Bundesanstalt (PTB) is based on the primary detector standard SYRES, a cryogenic electrical substitution radiometer capable of measuring radiant power of a few micro W. At the PTB radiometry laboratory at the synchrotron radiation facility BESSY, two dedicated beamlines are operated, providing monochromatic radiation of high spectral purity, high radiant power and tunable photon energy in the 3-1500 eV range. The spectral responsivity of detectors, e.g. photodiodes, can be measured with a relative uncertainty of about 1% by direct comparison with SYRES, as will be demonstrated for PtSi/Si and GaAsP/Au Schottky and silicon n-on-p photodiodes. The calibration of photon-counting detectors traceable to SYRES can by accomplished by exploiting the unique capability to scale the spectral photon flux over several orders of magnitude by changing the stored electron current. Calibrations of CCDs and photomultipliers are presented as examples.

Journal Article↗
PubMed1998

Components for the X-ray radiometry beamline at BESSY II.

Optical components for the X-ray radiometry beamline of the Physikalisch-Technische Bundesanstalt at BESSY II were investigated at BESSY I. Reflectometry measurements on different mirror coatings were used to calculate their capability to suppress higher-order radiation. An MgF(2) coating proved to be best suited for photon energies below 4 keV. The reflectance of silicon (111) monochromator crystals at low photon energies around 2 keV was homogeneous within +/-1%. In a test at a superconducting wavelength shifter the cooling system for the first crystal was shown to cope with the absorbed power of 14 W.

Journal Article↗
PubMed2002

Radiometry in line-shape modeling of Fourier-transform spectrometers.

A radiometric model of the instrument line shape (ILS) of Fourier-transform spectrometers is presented. We show first that common line-shape models are based on distribution of the radiant intensity in the interferometer. The complete steps between the source and the ILS are exposed as the core of the model. Relationships between the ILS, the spectrum as measured by the instrument, and the spectrum as emitted by the scene are demonstrated from the ILS model. Then the formal radiometric modeling of the ILS is derived, including the contribution of the aperture of the optical system. The particular case of a centered circular aperture with a uniform Lambertian radiance in the field of view is discussed. Conditions are deduced to ensure that the only spectral variation of the ILS is a scaling with wave number, as is usually assumed in current line-shape models. The ILS dependence on the scene is also discussed, and the effect of taking into account the radiometry on the ILS is estimated for the case of an ideal thin lens used as a collimator.

Journal Article↗
PubMed2003

Diffraction loss in radiometry.

Diffraction loss in radiometry has gained in importance recently because of an increased interest in longer wavelengths and the continuous improvement in experimental accuracy. The deviation from geometrical optics now contributes significantly to the errors of experiments. Previous research has concentrated on geometries classified as F1 and F2, leaving an intermediate case yet to be investigated. This intermediate case has some interesting behavior, as it is in this envelope of geometries that it is possible to have zero diffraction loss. We designate this intermediate geometric regime as F3. We introduce a numerical regime to calculate diffraction loss for intermediate geometries, which is also highly efficient for the F1 and F2 regimes.

Journal Article↗
PubMed2004

Passive remote monitoring of chemical vapors by differential Fourier-transform infrared radiometry: results at a range of 1.5 km.

A method for the passive remote monitoring of chemical vapors by differential Fourier-transform infrared radiometry is presented to determine the characteristics of a chemical vapor plume from a stack located at a distance of more than 1 km from the sensor. This measurement technique is based on the use of a double-beam Fourier-transform infrared spectrometer that is optimized for optical subtraction. A description of the interferometer (compact atmospheric sounding interferometer) is given along with the algorithm (GASEM) that has been developed for the on-line detection, identification, and quantification of chemical vapor plumes. The detection method is described with a particular emphasis placed on its monitoring capabilities. The analysis focuses on the experimental results obtained at a recent open-air experiment for vapor plume mixtures of dimethyl methyl phosphonate and SF6 probed at a distance of 1.5 km. The accuracy of a simplified plume radiance model implemented in the detection algorithm is specifically addressed. The measurement technique has been successfully used to detect and identify low, medium, and high concentrations of vapor mixtures but appears to have limited quantification capabilities in its present form.

Journal Article↗
PubMed2004

Multiband fiber optic radiometry for measuring the temperature and emissivity of gray bodies of low or high emissivity.

Infrared fiber optic radiometry was used for noncontact thermometry of gray bodies whose temperature was close to room temperature (40-70 degrees C). We selected three gray bodies, one with high emissivity (epsilon = 0.97), one with medium emissivity (epsilon = 0.71), and one with low emissivity (epsilon = 0.025). We carried out optimization calculations and measurements for a multiband fiber optic radiometer that consisted of a silver halide (AgClBr) infrared-transmitting fiber, a dual-band cooled infrared detector, and a set of 18 narrowband infrared filters that covered the 2-14-microm spectral range. We determined the optimal spectral range, the optimal number of filters to be used, and the optimal chopping scheme. Using these optimal conditions, we performed measurements of the three gray bodies and obtained an accuracy of better than 1 degrees C for body temperature and for room temperature. An accuracy of 0.03 was obtained for body emissivity.

Journal Article↗
PubMed2004

Passive standoff detection of radiological products by Fourier-transform infrared radiometry.

A preliminary investigation is made into the possibility of applying the passive standoff detection technique to the identification of radiological and related products. This work is based on laboratory measurements of the diffuse reflectance from a number of products, including U3O8, CsI, SrO, I2O5, and La2O3. These reflectances are incorporated into the MODTRAN4 radiative-transfer model to simulate the nadir radiance from surfaces consisting of these radiological or related materials. The simulations are performed for two situations: at an altitude of 1 m above the ground, to simulate the passive detection of nuclear products with a hand-held instrument, and at an altitude of 1 km, to simulate a passive sensor carried aboard an aircraft. The results of the simulations under idealized conditions, as well as the results of one measurement, show that the passive standoff detection of radiological products by Fourier-transform infrared radiometry may be possible.

Journal Article↗
PubMed2005

Passive standoff detection of SF6 at a distance of 5.7 km by differential Fourier transform infrared radiometry.

Recent results are presented on the passive detection, identification, and quantification of a vapor cloud of SF6 measured at a horizontal standoff distance of 5.7 km using a dual-beam interferometer optimized for background signal suppression. The measurements were performed at Defense Research and Development Canada (DRDC)-Valcartier during a number of recent open-air experiments. The measurement approach is based on the differential passive standoff detection method that has been developed by DRDC Valcartier during the past few years. This work represents the first such measurement reported in the open literature for a standoff distance as large as 5.7 km. These results clearly demonstrate the capability of the differential radiometry approach to the detection, identification, and quantification of chemical vapor clouds located at long distances from the sensor.

Air Pollutants↗
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↗
PubMed1988

[Whole-body radiometry in the evaluation of the absorptive and motor-evacuatory functions of the small and large intestines].

It is known that pathology of the small and large intestine, particularly in their total involvement, is accompanied by disturbance of the processes of digestion and absorption of fatty acids, proteins and vitamins. The existing methods for a study of absorption are complex and inadequate. The author proposed a comprehensive radionuclide study using whole-body radiometry permitting simultaneous assessment of motor-evacuatory function of the stomach, absorptive and motor-evacuatory function of the small and large intestines. Altogether 15 persons (controls) and 26 patients with inflammatory diseases of the large intestine were examined. The results of the study made it possible to detect disorders of digestion and absorption in the study group. The results should be taken into account for a choice of pathogenetically founded therapy in patients with inflammatory diseases of the small and large intestine.

Adult↗
PubMed1987

Sodium metabolism in Wistar rats during a chronic high-salt or a low-protein diet: 22Na determination by radiometry.

Whole body radiometry was employed to monitor 22Na radionuclide metabolism in Wistar rats of either sex, aged six months and 1.3 years, kept under normal conditions or on a low-protein diet or during chronic salt load over a period of one year. In all the groups studied, the differences in sodium metabolism according to sex and age were determined. Tissue sodium metabolism was statistically significantly slowed (p less than 0.001) in male and female rats on a high-salt diet compared with the control group. Renal sodium excretion was significantly increased in the high-salt diet group. In the low-protein diet group, tissue sodium metabolism was significantly faster than in control animals, and this both in female (p less than 0.01) and male rats (p less than 0.001). Renal sodium excretion was, however, significantly lower in male rats (p less than 0.001) than in control animals.

Animals↗
PubMed1986

[Iodine metabolism in leprosy patients (study using a whole-body radiometry method)].

A method of total body radiometry was used to study iodine metabolism in 47 patients with lepromatous leprosy. Disorders were found in 1/3 of the cases. The level of organic iodine in the body was the most informative of all iodine metabolism indices. In the active stage of leprosy it was twice as low, on an average, as the normal one, in the stage of incomplete and stable regression it rose not reaching, however, the values of healthy persons. The lowest mean value of an organic iodine level in the body was observed in patients with noticeable specific polyneuritis. The content of iodine in the thyroid of leprosy patients showed a tendency to a rise starting from the active stage, however it was only in the stages of incomplete and stable regression that it significantly exceeded the normal level. The data obtained should be considered during therapy of lepers to predict and control an unfavorable complication like specific polyneuritis.

Adult↗
PubMed1980

Modifications in biphasic liquid-scintillation vial system for radiometry.

Several modifications of the biphasic liquid-scintillation vial system for radiometry have been tried in order to improve the counting efficiency. The biphasic system consisted of an inner sterile vial containing medium and substrate, and an outer liquid-scintillation vial lined on the inside with filter paper impregnated with scintillation fluors and alkali. The system gave an overall counting efficiency of 14.6%. Substitution of methanolic NaOH for impregnation of the paper raised the counting efficiency to 29.1%. This could be further enhanced to 33.8% by lining only half of the outer vial with filter paper, thereby allowing improved optical transmission of scintillation light. Increasing the amount of fluor did not change the efficiency significantly. A complete interchange in the system, whereby half of the inner vial was lined with filter paper and was otherwise empty, while the outer vial contained the medium and substrate, gave the highest efficiency (36.9%). This also allowed the use of larger amounts of medium and the inoculum.

Carbon Dioxide↗