A. Mamouni

Microwave radiometric imaging at 3 GHz for the exploration of breast tumors

A process of microwave radiometric imaging at 3 GHz permits the mapping of radiometric intensities on a square area about half a decimeter on a side. These data, translated in terms of a colored image, point out the existence of lateral temperature gradients in tissues. This system was initially used for examining large breast tumors; at present, it is also used for detecting smaller, impalpable tumors. The rules for characterizing benignancy or malignancy of small tumors which appear in a mammographic examination (X-rays) are defined. The definition of an appropriate parameter, deduced from this image processing, makes it possible to indicate benignancy or malignancy. In experiments conducted on 18 patients, all the malignant lesions had a radiometric ratio greater than 65%, while benign lesions were below 55%. However, a zone of uncertainty (between 55% and 70%) exists where it is wise not to assert malignancy or benignancy. >

Non-invasive microwave radiometry thermometry

Near-field microwave radiometry and radiometric imaging are non-invasive techniques that are able to provide temperature information at a depth of up to several centimetres in subcutaneous tissues. They are based on the measurement of microwave electromagnetic thermal noise. This paper describes the basic principles, measurement methods and limitations of the techniques and the results of clinical studies, and it reviews recent progress.

Simultaneous microwave local heating and microwave thermography. Possible clinical applications.

A basic experiment showing the possibility of combining microwave local heating of subcutaneous living tissue, and microwave radiometry by the same system was carried out. The combined process may be used - in hyperthermia therapy, for measurement and control of the local temperature, - in some diagnoses using radiometry to detect diseased tissue.

Computation of near-field microwave radiometric signals: definition and experimental verification

A method is developed for computing the near field transmitted by a monomode rectangular waveguide aperture into a homogeneous lossy material. The principle of this method is discussed, and its results are verified by experiments both in an active process (when the antenna transmits a signal toward the material) and in a passive process (when the antenna receives the thermal noise transmitted by the different subvolumes of the material). The method has been applied to the computation of radiometric signals for both power and correlation radiometry. Comparison of the radiometric with experimental data points out quite a good agreement in the case of models made of water near 1.5 and 3 GHz. Consequently, this method of computing the radiometric signals can be used for medical applications, in which high-water-content tissues are often examined. >

Microwave short baseline interferometers for localization systems

Positioning determination is often associated with GPS or other complex techniques needing a central monitor station and precise reference time. For distances smaller than several tenths of meters, a simpler real-time method for determining position is described in this paper. This method is based on interferometry, whose features are mainly governed by geometrical parameters. This method is first tested by means of a prototype, operating at 10 GHz, with a test area of approximately 0.5 m/sup 2/, for which the location error is about 1 or 2 cm. The extension of this area size to several square decameters has been obtained at 2.45 GHz. For both situations, the size of the receiving system does not exceed 16 cm/spl times/16 cm.

Microwave Methods and Systems for Nondestructive Control

In the past the use of network analyzersfor measuring the electrical properties of materialsmakes the microwave techniques unsuitable for industrial purposes. Butrecently much attention has been paid to the development of microwave systems dedicated to the nondestructive testing of materials. In general these apparatus are designed for a given applicationso the cost in comparison with the network analyzer is considerably lower. The aim of this paper is to present results obtained from utilizing various configurations of original S-Parameters Measurement System (SPMS) constructed for practical use.

Near Field Microwave Radiometric Weighting Functions for Multilayered Materials

A modal method is used for the determination of the near field weighting functions related to the power transmitted from a rectangular waveguide aperture towards a lossy material and, by reciprocity, to the corresponding radiometric signals created by the thermal noise emission. This method is applied to homogeneous or multilayered material, such as in microwave radiometry applied to medicine for non invasive thermometry of the subcutaneous tissues. From the knowledge of the weighting functions, we propose a new definition for the volume of material coupled with the probe, as radiometric measurement terms. We present examples of such coupled volumes, as a function of frequency or size of the probe.

Microwave Radiometry Imaging: Characterization of Breast Tumours

AbstractA microwave imaging (MI) device working at 3 GHz has been used to record temperature images of early breast tumours. 25 patients were investigated prior to surgery. For every patient, the excised tissue was examined histologically. 22 of these patients were found to have only benign lesions using both MI and histology. Histology and MI found a malignant tumour for 3 patients. In all the 25 selected patients we were unable to determine the nature of the tumours by clinical examination, X-ray mammography and cytology. The results of the microwave imaging obtained in this study are therefore encouraging in the detection of cancer

Passive Subcutaneous Temperature Measurement for Investigation of Thermoregulation

Passive microwave sensors allow subcutaneous temperature measurements in living tissues. A previously presented method was improved and probes were carried out. The accuracy of this apparatus, which works at 9 GHzwith a bandwidth 1 GHz, is tested on lossy liquids and on living tissues (animal). In the case of man, variations of subcutaneous temperature (radiometric method) and skin temperature (thermocouple) are recorded during physical activity. The difference between these two sets of results shows the importance of this non invasive thermographic method for thermoregulation investigation.

Non Destructive Thermometry by Means of Microwave Radiometry

The measurement of the thermal noise transmitted by lossy materials in the microwave frequency range is, at the present time, the only one thermometric method able to bring information about the temperature distribution inside a material without insertion of any sensor. In this paper, we first briefly recall the principles of the method, and the present state of the experimental set-ups. This technique interest quite different domains of applications such as industrial thermometry, biomedicai engineering, domotics and microelectronics. In other words, the presentation is related to different situations: ∼ material at uniform or non uniform temperatures ∼ temperatures over or beneath the room, or reference temperature ∼ different materials: high or low losses, homogeneous, multilayered or heterogeneous ∼ measurement of a thermal noise temperature or of a correlation temperature. The paper analyses also the reasons why these method have not still much penetrated the industrial market and explains the arguments for a future extension of these kinds of applications.