J.C. van de Velde

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

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.

Contactless Thermometry of a Textile Web by Microwave Radiometry

We present a new application of microwave radiometry devoted to the contactless thermometry of a textile web. An interpretation of the radiometric data is proposed. It is also shown in which way this process can be used to determine a thermal profile which exists along the web.

A Clinical Evaluation of Microwave Radiometric Imaging About Characterisation of Non Palpable Breast Tumours

Microwave radiometric imaging, i.e. the processing of a lot of radiometric data measured at different points of an area, is able to provide information about temperature gradients at a depth of up to several centimetres in the subcutaneous tissues. The present study starts again a clinical evaluation about diagnosis in cancerology undertaken previously, but with new means in terms of radiometric equipment and data processing. The clinical problem that is being tackled today is the characterisation of non-palpable breast tumours in terms of benignity or malignancy. In fact, the current diagnosis methods lead to too-many false negative answers and unnecessary surgery on some type of tumours. The aim of this new clinical evaluation is to answer to the question: can microwave radiometric imaging work as a diagnosis tool for routine examination ? Beyond this direct medical benefit, the aim of this radiometric technique is a remote quantitative thermometry by means of inversion of the radiometric images. This process is realised by a deconvolution of the absolute weighting functions and a regularisation procedure.

Thermal Response of a Lossy Two-Ports to a Correlation Radiometer

We consider the output signal of a correlation radiometer connected to an isothermal lossy two-ports, such as lossy microstrip lines and coaxial lines filled with a lossy dielectric.

Computation of Three-dimensional Radiometric Signals Detected in Microwave Imaging

AbstractThe present development of microwave radiometry for medical applications encourages the development of methods for computer modelling of the radiometric thermal signals transmitted by living tissues. This method, considers both homogeneous and multilayered tissues. We present here computed data for the definition of microwave radiometric imaging and for the interpretation of radiometric data.

Microwave Thermal Imaging by Radiometry

Microwave radiometry appears to be well suited for treating thermological investigations devoted to moderately deep seated tissues. These investigations are used in diagnosis and follow up methods (for example in the detection of thermogen tissues, or inflammations such as those consecutive to acute ionization radiations...) and also for the monitoring of local heating in hyperthermia. We emphasize a process leading to radiometric imaging, present images obtained in medical examinations, and present in which way we determine the characteristics of a compact thermal volume by the processing of radiometric data obtained at two frequencies.

Microwave radiometric imaging (M.W.I) for subcutaneous thermal investigation

Microwave radiometry, i.e the measurement of the thermal noise spontaneously transmitted by matter, is at the origin of non-contact thermometry. Applied to living tissues, it brings information about the subcutaneous temperatures.[1]

Progress in Microwave Thermography

The principle of microwave thermography (MWT) is mainly based on two factors: all bodies emit electromagnetic radiation, the intensity of which depends upon the temperature of the body; living tissues absorb microwaves generated at depths of several centimeters.