P.-Y. Cresson

Complete three-dimensional modeling of new microstrip-microslot applicators for microwave hyperthermia using the FDTD method

Describes a complete 3D modeling using the finite difference time domain (FDTD) method of a new generation of external applicators for microwave hyperthermia used at either at 434 MHz or 915 MHz without any modifications. With this new model, it is possible to obtain theoretical results concerning the variations of the reflection coefficient as a function of frequency, the power deposition inside the heated lossy tissues and the heating patterns. Experimental electromagnetic and thermal characteristics are presented and compared with the theoretical results obtained with the 3D method. >

Complete three-dimensional modeling of new microstrip-microslot applicators for microwave hyperthermia using F.D.T.D. method

Describes a complete 3D modeling using the finite difference time domain (FDTD) method of a new generation of external applicators for microwave hyperthermia used at either at 434 MHz or 915 MHz without any modifications. With this new model, it is possible to obtain theoretical results concerning the variations of the reflection coefficient as a function of frequency, the power deposition inside the heated lossy tissues and the heating patterns. Experimental electromagnetic and thermal characteristics are presented and compared with the theoretical results obtained with the 3D method.<<ETX>>

Temperature Measurement by Microwave Radiometry: Application to Microwave Sintering

Temperature is a key parameter in industrial manufacturing, and its control is very often directly related to the quality of the products. Microwave-assisted processing has gained worldwide acceptance in powder technologies, in particular for the sintering of ceramic parts. High-energy efficiency, fast heating rate, and new and improved properties of the materials are typically observed. For example, fully dense bodies could be produced with improved mechanical properties due to the finer grain size. In fast-processing conditions, the system is mostly out of thermal equilibrium. A complex temperature-distribution pattern develops inside the heated parts, which can lead to localized melting or detrimental distortions if it is not under control. Today, none of the available thermometric methods (thermocouples, optical fiber, infrared, etc.) gives access to this volumetric information. We propose the use of microwave radiometry to noninvasively measure and control the temperature during the microwave sintering processes.

Temperature Measurement by Microwave Radiometry

Temperature is an important parameter in the industrial world. For example, temperature control is of a greater concern in food processing industry for safety reasons as well as for product quality. Recently, microwave processing of powder metallurgical bodies has been shown to be very promising. Fully dense bodies with improved mechanical properties could be produced due to finer grain size. In the field of the sintering of materials, a control of the temperature inside heated parts is necessary to avoid local melting or distortions. The medical field is another sector particularly interested in non invasive techniques for the measurement of human temperature. In fact, the corporal temperature is proved to be a pertinent parameter in the scope of diagnosis, monitoring of many pathologies and for the posology of some medicines. None of the current methods for measuring temperature (thermocouples, optic fibers, infrared, etc...) give by a non-invasive way continuous temperature information. So, microwave radiometry brings a neat solution to measure and control non-invasively temperature inside a dissipative material. This paper is concerning the design and the realization of specific radiometric sensors in order to measure and control temperatures from a non-invasive way by microwave radiometry either in industrial or in medical applications.

Design and modeling of a specific microwave applicator for the treatment of snoring

One of the main objectives of using microwaves in medical applications is to make use of the therapeutic effects resulting from the interaction between electromagnetic waves and biological tissues in order to obtain a local heating. For this purpose, a large number of devices have been designed and tested for various medical applications. We present in this paper the results concerning the design and the modeling of an applicator developed for the treatment of snoring using microwaves.

Design and modeling of multipatches planar applicators for microwave hyperthermia

Describes a new type of external planar applicator with several patches which have been developed for microwave hyperthermia controlled by microwave radiometry. The possibility to obtain larger heating patterns than with the single patch applicators is clearly focused by the theoretical results which are presented and verified by experimental measurements.<<ETX>>

Non invasive Determination of Temperature Trajectories During a Defrosting Process using Microwave Radiometry

The control of the freezing or defrosting velocity is an important parameter in food industries, for the improvement of product quality. In this paper, radiometric measurements, a noninvasive method, are shown to be effective to follow the defrosting of foodstuff. We describe experiments and the radiometric device used. Simulations based upon the combined algorithms FDTD - heat transport equation are used to predict the radiometric temperature trajectories during the defrosting process by introducing the temperature dependent media. The comparisons between experimental and theoretical results are presented and analyzed.

Design and modeling using the FDTD method of planar multi-applicators for microwave hyperthermia

Describes a new kind of external planar applicators with several patches called multi-applicator which have been developed for microwave hyperthermia controlled by microwave radiometry. The possibility to obtain larger heating patterns than with a single patch applicator is clearly focused by the theoretical results which are presented and verified by experimental measurements.

Bidimensional analysis of planar applicators from spectral domain approach method for 915 MHz hyperthermia

A two-dimensional model of a microstrip-microslot resonator with a protective layer in contact with a multilayered lossy medium is presented. This analysis is based on the spectral domain approach (SDA). Theoretical and experimental results on the resonant frequencies, the power deposition, and the heating patterns of a planar applicator radiating into a human body or phantoms are presented. This work makes it possible to obtain the complex resonant frequency, i.e., the resonant frequency and the Q factor of the structure and the power deposition from which the thermal pattern can be obtained. Good agreement between two-dimensional theory and experiment is obtained. Therefore, this approach constitutes an additional numerical simulation tool which makes it possible to obtain a better optimization of the geometrical parameters of the applicator and to optimize the efficiency of hyperthermia treatments by a better knowledge of the temperature pattern in the heated tissues.<<ETX>>